{"id":2377,"date":"2019-07-23T21:04:42","date_gmt":"2019-07-24T01:04:42","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/chapter\/catalysis\/"},"modified":"2021-09-15T01:30:47","modified_gmt":"2021-09-15T05:30:47","slug":"catalysis","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/chapter\/catalysis\/","title":{"raw":"4.6 Catalysis","rendered":"4.6 Catalysis"},"content":{"raw":"[latexpage]\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Learning Objectives<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Explain the function of a catalyst in terms of reaction mechanisms and potential energy diagrams<\/li>\r\n \t<li>List examples of catalysis in natural and industrial processes<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<p id=\"fs-idm241568976\">Among the factors affecting chemical reaction rates discussed earlier in this chapter was the presence of a <em data-effect=\"italics\">catalyst<\/em>, a substance that can increase the reaction rate without being consumed in the reaction. The concepts introduced in the previous section on reaction mechanisms provide the basis for understanding how catalysts are able to accomplish this very important function.<\/p>\r\n<p id=\"fs-idm627108512\"><a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_CatReCoDig\">(Figure 4.6.1)<\/a> shows reaction diagrams for a chemical process in the absence and presence of a catalyst. Inspection of the diagrams reveals several traits of these reactions. Consistent with the fact that the two diagrams represent the same overall reaction, both curves begin and end at the same energies (in this case, because products are more energetic than reactants, the reaction is endothermic). The reaction mechanisms, however, are clearly different. The uncatalyzed reaction proceeds via a one-step mechanism (one transition state observed), whereas the catalyzed reaction follows a two-step mechanism (two transition states observed) with <em data-effect=\"italics\">a notably lesser activation energy<\/em>. This difference illustrates the means by which a catalyst functions to accelerate reactions, namely, by providing an alternative reaction mechanism with a lower activation energy. Although the catalyzed reaction mechanism for a reaction needn\u2019t necessarily involve a different number of steps than the uncatalyzed mechanism, it must provide a reaction path whose rate determining step is faster (lower <em data-effect=\"italics\">E<\/em><sub>a<\/sub>).<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_CatReCoDig\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\"><em>\u00a0\u00a0<\/em><\/div>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"650\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2019\/07\/CNX_Chem_12_07_CatReCoDig-1-1.jpg\" alt=\"A graph is shown with the label, \u201cExtent of reaction,\u201d appearing in a right pointing arrow below the x-axis and the label, \u201cEnergy,\u201d in an upward pointing arrow just left of the y-axis. Approximately one-fifth of the way up the y-axis, a very short, somewhat flattened portion of both a red and a blue curve are shown. This region is labeled \u201cReactants.\u201d A red concave down curve extends upward to reach a maximum near the height of the y-axis. From the peak, the curve continues downward to a second horizontally flattened region at a height of about one-third the height of the y-axis. This flattened region is labeled, \u201cProducts.\u201d A second curve is drawn in blue with the same flattened regions at the start and end of the curve. The height of this curve is about two-thirds the height of the first curve and just right of its maximum, the curve dips low, then rises back and continues a downward trend at a lower height, but similar to that of the red curve. A horizontal dashed straight line extends from the point where both curves start in the \u201cReactants\u201d region. A double sided arrow extends from the \u201cProducts\u201d region at the end of both curves to this horizontal dashed line. This is labeled \u201ccapital delta H.\u201d A double sided arrow extends from the dashed horizontal line to the peak of the red concave down curve. This arrow is labeled \u201cE subscript a.\u201d Another double sided arrow extends from the dashed horizontal line to the peak of the blue curve. This arrow is labeled \u201cE subscript a.\u201d\" width=\"650\" height=\"567\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.1 - Reaction diagrams for an endothermic process in the absence (red curve) and presence (blue curve) of a catalyst. The catalyzed pathway involves a two-step mechanism (note the presence of two transition states) and an intermediate species (represented by the valley between the two transitions states).<\/strong>[\/caption]\r\n\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Activity 4.6.1 - Reaction Diagrams for Catalyzed Reactions<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nThe two reaction diagrams here represent the same reaction: one without a catalyst and one with a catalyst. Estimate the activation energy for each process, and identify which one involves a catalyst.\r\n\r\n<span id=\"fs-idm142234720\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy ( k J ).\u201d The y-axes are marked off from 0 to 50 in intervals of five. In a, a blue curve is shown. It begins with a horizontal segment at about 6. The curve then rises sharply near the middle to reach a maximum of about 32 and similarly falls to another horizontal segment at about 10. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\"><img class=\"aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Rxndiagramex_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy ( k J ).\u201d The y-axes are marked off from 0 to 50 in intervals of five. In a, a blue curve is shown. It begins with a horizontal segment at about 6. The curve then rises sharply near the middle to reach a maximum of about 32 and similarly falls to another horizontal segment at about 10. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<h2 id=\"fs-idm154613456\">Solution<\/h2>\r\nActivation energies are calculated by subtracting the reactant energy from the transition state energy.\r\n\r\n&nbsp;\r\n<div id=\"fs-idm239782272\" data-type=\"equation\">\\(\\begin{array}{c}\\text{diagram (a):}\\phantom{\\rule{0.2em}{0ex}}{E}_{\\text{a}}=32\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}-6\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}=26\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}\\hfill \\\\ \\text{diagram (b):}\\phantom{\\rule{0.2em}{0ex}}{E}_{\\text{a}}=20\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}-6\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}=14\\phantom{\\rule{0.2em}{0ex}}\\text{kJ}\\hfill \\end{array}\\)<\/div>\r\n<div data-type=\"equation\"><em>\u00a0\u00a0<\/em><\/div>\r\n<p id=\"fs-idm202838144\">The catalyzed reaction is the one with lesser activation energy, in this case represented by diagram b.<\/p>\r\n\r\n<h2 id=\"fs-idm163597616\"><span data-type=\"title\">Check Your Learning<\/span><\/h2>\r\nReaction diagrams for a chemical process with and without a catalyst are shown below. Both reactions involve a two-step mechanism with a rate-determining first step. Compute activation energies for the first step of each mechanism, and identify which corresponds to the catalyzed reaction. How do the second steps of these two mechanisms compare?\r\n\r\n<span id=\"fs-idm153634048\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeledc \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 100 at intervals of 10. In a, a blue curve is shown. It begins with a horizontal segment at about 10. The curve then rises sharply near the middle to reach a maximum of about 91, then sharply falls to about 52, again rises sharply to about 73 and falls to another horizontal segment at about 5. In b, the curve begins and ends similarly, but the first peak reaches about 81, drops to about 55, then rises to about 77 before falling to the horizontal region at about 5.\"><img class=\"aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Rxndiagramcyl_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeledc \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 100 at intervals of 10. In a, a blue curve is shown. It begins with a horizontal segment at about 10. The curve then rises sharply near the middle to reach a maximum of about 91, then sharply falls to about 52, again rises sharply to about 73 and falls to another horizontal segment at about 5. In b, the curve begins and ends similarly, but the first peak reaches about 81, drops to about 55, then rises to about 77 before falling to the horizontal region at about 5.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<div id=\"fs-idm215189760\" data-type=\"note\">\r\n<h3 style=\"text-align: right\" data-type=\"title\">Answer<\/h3>\r\n<p id=\"fs-idm239441760\" style=\"text-align: right\">For the first step, <em data-effect=\"italics\">E<\/em><sub>a<\/sub> = 80 kJ for (a) and 70 kJ for (b), so diagram (b) depicts the catalyzed reaction. Activation energies for the second steps of both mechanisms are the same, 20 kJ.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\r\n<h2 data-type=\"title\">Homogeneous Catalysts<\/h2>\r\n<p id=\"fs-idm243256336\">A <span data-type=\"term\">homogeneous catalyst<\/span> is present in the same phase as the reactants. It interacts with a reactant to form an intermediate substance, which then decomposes or reacts with another reactant in one or more steps to regenerate the original catalyst and form product. As an important illustration of homogeneous catalysis, consider the earth\u2019s ozone layer. Ozone in the upper atmosphere, which protects the earth from ultraviolet radiation, is formed when oxygen molecules absorb ultraviolet light and undergo the reaction:<\/p>\r\n\r\n<div id=\"fs-idm276049600\" data-type=\"equation\">\\(3{\\text{O}}_{2}\\left(g\\right)\\stackrel{\\phantom{\\rule{0.7em}{0ex}}hv\\phantom{\\rule{0.7em}{0ex}}}{\\to }2{\\text{O}}_{3}\\left(g\\right)\\)<\/div>\r\n<p id=\"fs-idm291675632\">Ozone is a relatively unstable molecule that decomposes to yield diatomic oxygen by the reverse of this equation. This decomposition reaction is consistent with the following two-step mechanism:<\/p>\r\n\r\n<div id=\"fs-idm37859104\" data-type=\"equation\">\\(\\begin{array}{}\\\\ {\\text{O}}_{3}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{O}}_{2}+\\text{O}\\\\ \\text{O}+{\\text{O}}_{3}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}2{\\text{O}}_{2}\\end{array}\\)<\/div>\r\n<p id=\"fs-idm103646832\">A number of substances can catalyze the decomposition of ozone. For example, the nitric oxide\u2013catalyzed decomposition of ozone is believed to occur via the following three-step mechanism:<\/p>\r\n\r\n<\/div>\r\n&nbsp;\r\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\r\n<div id=\"fs-idm109392\" data-type=\"equation\">\\(\\begin{array}{}\\\\ \\text{NO}\\left(g\\right)+{\\text{O}}_{3}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{NO}}_{\\text{2}}\\left(g\\right)+{\\text{O}}_{\\text{2}}\\left(g\\right)\\\\ {\\text{O}}_{3}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{O}}_{2}\\left(g\\right)+\\text{O}\\left(g\\right)\\\\\u00a0{\\text{NO}}_{2}\\left(g\\right)+\\text{O}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{NO}\\left(g\\right)+{\\text{O}}_{2}\\left(g\\right)\\end{array}\\)<\/div>\r\n<\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<div data-type=\"equation\"><span style=\"text-align: initial;font-size: 1em\">As required, the overall reaction is the same for both the two-step uncatalyzed mechanism and the three-step NO-catalyzed mechanism:<\/span><\/div>\r\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\r\n\r\n&nbsp;\r\n<div id=\"fs-idm46801248\" data-type=\"equation\">\\(2{\\text{O}}_{3}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}3{\\text{O}}_{2}\\left(g\\right)\\)<\/div>\r\n<p id=\"fs-idm251830192\">Notice that NO is a reactant in the first step of the mechanism and a product in the last step. This is another characteristic trait of a catalyst: Though it participates in the chemical reaction, it is not consumed by the reaction.<\/p>\r\n\r\n<div id=\"fs-idm195911072\" class=\"chemistry chemist-portrait\" data-type=\"note\">\r\n<h2 data-type=\"title\">Mario J. Molina<\/h2>\r\n<p id=\"fs-idm149608448\">The 1995 Nobel Prize in Chemistry was shared by Paul J. Crutzen, Mario J. <span class=\"no-emphasis\" data-type=\"term\">Molina<\/span> (<a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Molina\">Figure 4.6.2<\/a>), and F. Sherwood Rowland \u201cfor their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone.\u201d[footnote]\u201cThe Nobel Prize in Chemistry 1995,\u201d Nobel Prize.org, accessed February 18, 2015, http:\/\/www.nobelprize.org\/nobel_prizes\/chemistry\/laureates\/1995\/[\/footnote] Molina, a Mexican citizen, carried out the majority of his work at the Massachusetts Institute of Technology (MIT).<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_Molina\" class=\"bc-figure figure\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1200\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Molina-1.jpg\" alt=\"A photograph is shown of Mario Molina. To the right of the photo, an image of Earth\u2019s southern hemisphere is shown with a central circular region in purple with a radius of about half that of the entire hemisphere. Just outside this region is a narrow royal blue band, followed by an outer thin turquoise blue band. The majority of the outermost region is green. Two small bands of yellow are present in the lower regions of the image.\" width=\"1200\" height=\"511\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.2 - (a) Mexican chemist Mario Molina (1943 \u2013) shared the Nobel Prize in Chemistry in 1995 for his research on (b) the Antarctic ozone hole. (credit a: courtesy of Mario Molina; credit b: modification of work by NASA)<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-idm242073328\">In 1974, Molina and Rowland published a paper in the journal <em data-effect=\"italics\">Nature<\/em> detailing the threat of chlorofluorocarbon gases to the stability of the ozone layer in earth\u2019s upper atmosphere. The ozone layer protects earth from solar radiation by absorbing ultraviolet light. As chemical reactions deplete the amount of ozone in the upper atmosphere, a measurable \u201chole\u201d forms above Antarctica, and an increase in the amount of solar ultraviolet radiation\u2014 strongly linked to the prevalence of skin cancers\u2014reaches earth\u2019s surface. The work of Molina and Rowland was instrumental in the adoption of the Montreal Protocol, an international treaty signed in 1987 that successfully began phasing out production of chemicals linked to ozone destruction.<\/p>\r\n<p id=\"fs-idm4297296\">Molina and Rowland demonstrated that chlorine atoms from human-made chemicals can catalyze ozone destruction in a process similar to that by which NO accelerates the depletion of ozone. Chlorine atoms are generated when chlorocarbons or chlorofluorocarbons\u2014once widely used as refrigerants and propellants\u2014are photochemically decomposed by ultraviolet light or react with hydroxyl radicals. A sample mechanism is shown here using methyl chloride:<\/p>\r\n\r\n<div id=\"fs-idm241556704\" data-type=\"equation\">\\({\\text{CH}}_{3}\\text{Cl}+\\text{OH}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{Cl}+\\text{other products}\\)<\/div>\r\n<p id=\"fs-idm211108656\">Chlorine radicals break down ozone and are regenerated by the following catalytic cycle:<\/p>\r\n\r\n<div id=\"fs-idm150620768\" data-type=\"equation\">\\(\\begin{array}{}\\\\ \\text{Cl}+{\\text{O}}_{3}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{ClO}+{\\text{O}}_{2}\\\\ \\text{ClO}+\\text{O}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{Cl}+{\\text{O}}_{2}\\\\ \\text{overall Reaction:}\\phantom{\\rule{0.2em}{0ex}}{\\text{O}}_{3}+\\text{O}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}2{\\text{O}}_{2}\\end{array}\\)<\/div>\r\n<p id=\"fs-idm225343040\">A single monatomic chlorine can break down thousands of ozone molecules. Luckily, the majority of atmospheric chlorine exists as the catalytically inactive forms Cl<sub>2<\/sub> and ClONO<sub>2<\/sub>. Since receiving his portion of the Nobel Prize, Molina has continued his work in atmospheric chemistry at MIT.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm220632992\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\r\n<h2 data-type=\"title\">Glucose-6-Phosphate Dehydrogenase Deficiency<\/h2>\r\n<p id=\"fs-idm119819152\">Enzymes in the human body act as catalysts for important chemical reactions in cellular metabolism. As such, a deficiency of a particular enzyme can translate to a life-threatening disease. G6PD (glucose-6-phosphate dehydrogenase) deficiency, a genetic condition that results in a shortage of the enzyme glucose-6-phosphate dehydrogenase, is the most common enzyme deficiency in humans. This enzyme, shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Gluc6PhoDe\">(Figure 4.6.3)<\/a>, is the rate-limiting enzyme for the metabolic pathway that supplies NADPH to cells <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_HMPShuntPa\">(Figure 4.6.4)<\/a>.<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_Gluc6PhoDe\" class=\"scaled-down\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"351\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Gluc6PhoDe-1.jpg\" alt=\"A colorful model of the Glucose-6-phosphate dehydrogenase structure is shown. The molecule has two distinct lobes which are filled with spiraled ribbon-like regions of yellow, lavender, blue, silver, green, and pink.\" width=\"351\" height=\"272\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.3 -\u00a0Glucose-6-phosphate dehydrogenase is a rate-limiting enzyme for the metabolic pathway that supplies NADPH to cells.<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-idm227628064\">A disruption in this pathway can lead to reduced glutathione in red blood cells; once all glutathione is consumed, enzymes and other proteins such as hemoglobin are susceptible to damage. For example, hemoglobin can be metabolized to bilirubin, which leads to jaundice, a condition that can become severe. People who suffer from G6PD deficiency must avoid certain foods and medicines containing chemicals that can trigger damage their glutathione-deficient red blood cells.<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_HMPShuntPa\" class=\"bc-figure figure\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1200\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_HMPShuntPa-1.jpg\" alt=\"A reaction mechanism is diagrammed in this figure. At the left, the name Glucose is followed by a horizontal, right pointing arrow, labeled, \u201cHexokinase.\u201d Below this arrow and to the left is a yellow star shape labeled, \u201cA T P.\u201d A curved arrow extends from this shape to the right pointing arrow, and down to the right to a small brown oval labeled, \u201cA D P.\u201d To the right of the horizontal arrow is the name Glucose 6 phosphate, which is followed by another horizontal, right pointing arrow which is labeled, \u201cG 6 P D.\u201d A small orange rectangle below and left of this arrow is labeled \u201cN A D P superscript plus.\u201d A curved arrow extends from this shape to the right pointing arrow, and down to the right to a small salmon-colored rectangle labeled \u201cN A P D H.\u201d A curved arrow extends from this shape below and to the left, back to the orange rectangle labeled, \u201cN A D P superscript plus.\u201d Another curved arrow extends from a green oval labeled \u201cG S S G\u201d below the orange rectangle, up to the arrow curving back to the orange rectangle. This last curved arrow continues on to the lower right to a second green oval labeled, \u201cG S H.\u201d The end of this curved arrow is labeled, \u201cGlutathione reductase.\u201d To the right of the rightmost horizontal arrow appears the name 6 phosphogluconate.\" width=\"1200\" height=\"428\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.4 - In the mechanism for the pentose phosphate pathway, G6PD catalyzes the reaction that regulates NADPH, a co-enzyme that regulates glutathione, an antioxidant that protects red blood cells and other cells from oxidative damage.<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm254642320\" class=\"bc-section section\" data-depth=\"1\">\r\n<h2 data-type=\"title\">Heterogeneous Catalysts<\/h2>\r\n<p id=\"fs-idm31937584\">A <span data-type=\"term\">heterogeneous catalyst<\/span> is a catalyst that is present in a different phase (usually a solid) than the reactants. Such catalysts generally function by furnishing an active surface upon which a reaction can occur. Gas and liquid phase reactions catalyzed by heterogeneous catalysts occur on the surface of the catalyst rather than within the gas or liquid phase.<\/p>\r\n<p id=\"fs-idm52671504\">Heterogeneous catalysis typically involves the following processes:<\/p>\r\n\r\n<ol id=\"fs-idm202987392\" type=\"1\">\r\n \t<li>Adsorption of the reactant(s) onto the surface of the catalyst<\/li>\r\n \t<li>Activation of the adsorbed reactant(s)<\/li>\r\n \t<li>Reaction of the adsorbed reactant(s)<\/li>\r\n \t<li>Desorption of product(s) from the surface of the catalyst<\/li>\r\n<\/ol>\r\n<p id=\"fs-idm173407040\"><a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_HetCats\">(Figure 4.6.5)<\/a> illustrates the steps of a mechanism for the reaction of compounds containing a carbon\u2013carbon double bond with hydrogen on a nickel catalyst. Nickel is the catalyst used in the hydrogenation of polyunsaturated fats and oils (which contain several carbon\u2013carbon double bonds) to produce saturated fats and oils (which contain only carbon\u2013carbon single bonds).<\/p>\r\n<em>\u00a0\u00a0<\/em>\r\n<div id=\"CNX_Chem_12_07_HetCats\" class=\"scaled-down\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_HetCats-1.jpg\" alt=\"In this figure, four diagrams labeled a through d are shown. In each, a green square surface is shown in perspective to provide a three-dimensional appearance. In a, the label \u201cN i surface\u201d is placed above with a line segment extending to the green square. At the lower left and upper right, pairs of white spheres bonded tougher together appear as well as white spheres on the green surface. Black arrows are drawn from each of the white spheres above the surface to the white sphere on the green surface. In b, the white spheres are still present on the green surface. Near the center of this surface is a molecule with two central black spheres with a double bond indicated by two horizontal black rods between them. Above and below to the left and right, a total of four white spheres are connected to the black spheres with white rods. A line segment extends from this structure to the label, \u201cEthylene absorbed on surface breaking pi bonds.\u201d Just above this is a nearly identical structure greyed out with three downward pointing arrows to the black and white structure to indicate downward motion. The label \u201cEthylene\u201d at the top of the diagram is connected to the greyed out structure with a line segment. In c, the diagram is very similar to b except that the greyed out structure and labels are gone and one of the white spheres near the black and white structure in each pair on the green surface is greyed out. Arrows point from the greyed out white spheres to the double bond between the two black spheres. In d, only a single white sphere remains from each pair in the green surface. A curved arrow points from the middle of the green surface to a model above with two central black spheres with a single black rod indicating a single bond between them. Each of the black rods has three small white spheres bonded as indicated by white rods between the black spheres and the small white spheres. The four bonds around each black sphere are evenly distributed about the black spheres.\" width=\"975\" height=\"401\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.5 - Mechanism for the Ni-catalyzed reaction \\({\\text{C}}_{2}{\\text{H}}_{4}+{\\text{H}}_{2}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{C}}_{2}{\\text{H}}_{6}.\\) (a) Hydrogen is adsorbed on the surface, breaking the H\u2013H bonds and forming Ni\u2013H bonds. (b) Ethylene is adsorbed on the surface, breaking the C\u2013C \u03c0-bond and forming Ni\u2013C bonds. (c) Atoms diffuse across the surface and form new C\u2013H bonds when they collide. (d) C<sub>2<\/sub>H<sub>6<\/sub> molecules desorb from the Ni surface.<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-idm108887776\">Many important chemical products are prepared via industrial processes that use heterogeneous catalysts, including ammonia, nitric acid, sulfuric acid, and methanol. Heterogeneous catalysts are also used in the catalytic converters found on most gasoline-powered automobiles <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_CatConvert\">(Figure 4.6.6)<\/a>.<\/p>\r\n\r\n<h2><span style=\"font-family: 'Cormorant Garamond', serif;font-size: 1.602em\">Automobile Catalytic Converters<\/span><\/h2>\r\n<div id=\"fs-idm214293568\" class=\"chemistry everyday-life\" data-type=\"note\">\r\n<p id=\"fs-idm151500176\">Scientists developed catalytic converters to reduce the amount of toxic emissions produced by burning gasoline in internal combustion engines. By utilizing a carefully selected blend of catalytically active metals, it is possible to effect complete combustion of all carbon-containing compounds to carbon dioxide while also reducing the output of nitrogen oxides. This is particularly impressive when we consider that one step involves adding more oxygen to the molecule and the other involves removing the oxygen.<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_CatConvert\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\"><em>\u00a0 \u00a0<\/em><\/div>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"877\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_CatConvert-1.jpg\" alt=\"An image is shown of a catalytic converter. At the upper left, a blue arrow pointing into a pipe that enters a larger, widened chamber is labeled, \u201cDirty emissions.\u201d A small black arrow that points to the lower right is positioned along the upper left side of the widened region. This arrow is labeled, \u201cAdditional oxygen from air pump.\u201d The image shows the converter with the upper surface removed, exposing a red-brown interior. The portion of the converter closest to the dirty emissions inlet shows small, round components in an interior layer. This layer is labeled \u201cThree-way reduction catalyst.\u201d The middle region shows closely packed small brown rods that are aligned parallel to the dirty emissions inlet pipe. The final quarter of the interior of the catalytic converter again shows a layer of closely packed small red brown circles. Two large light grey arrows extend from this layer to the open region at the lower right of the image to the label \u201cClean emissions.\u201d\" width=\"877\" height=\"533\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.6 - A catalytic converter allows for the combustion of all carbon-containing compounds to carbon dioxide, while at the same time reducing the output of nitrogen oxide and other pollutants in emissions from gasoline-burning engines.<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-idm247003792\">Most modern, three-way catalytic converters possess a surface impregnated with a platinum-rhodium catalyst, which catalyzes the conversion of nitric oxide into dinitrogen and oxygen as well as the conversion of carbon monoxide and hydrocarbons such as octane into carbon dioxide and water vapor:<\/p>\r\n<em>\u00a0\u00a0<\/em>\r\n<div id=\"fs-idm216459392\" data-type=\"equation\">\\(\\begin{array}{l}2{\\text{NO}}_{\\text{2}}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{N}}_{\\text{2}}\\left(g\\right)+2{\\text{O}}_{\\text{2}}\\left(g\\right)\\\\ 2{\\text{CO}}\\left(g\\right)+{\\text{O}}_{2}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}2{\\text{CO}}_{\\text{2}}\\left(g\\right)\\\\ 2{\\text{C}}_{8}{\\text{H}}_{18}\\left(g\\right)+25{\\text{O}}_{2}\\left(g\\right)\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}16{\\text{CO}}_{2}\\left(g\\right)+18{\\text{H}}_{2}\\text{O}\\left(g\\right)\\end{array}\\)<\/div>\r\n<div data-type=\"equation\"><em>\u00a0\u00a0<\/em><\/div>\r\n<p id=\"fs-idm228107536\">In order to be as efficient as possible, most catalytic converters are preheated by an electric heater. This ensures that the metals in the catalyst are fully active even before the automobile exhaust is hot enough to maintain appropriate reaction temperatures.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm194237936\" class=\"chemistry link-to-learning\" data-type=\"note\">\r\n<p id=\"fs-idm266375520\">The University of California at Davis\u2019 \u201cChemWiki\u201d provides a <a href=\"http:\/\/openstaxcollege.org\/l\/16catconvert\">thorough explanation<\/a> of how catalytic converters work.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm26203536\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\r\n<h2 data-type=\"title\">Enzyme Structure and Function<\/h2>\r\n<p id=\"fs-idm220395040\">The study of enzymes is an important interconnection between biology and chemistry. Enzymes are usually proteins (polypeptides) that help to control the rate of chemical reactions between biologically important compounds, particularly those that are involved in cellular metabolism. Different classes of enzymes perform a variety of functions, as shown in <a class=\"autogenerated-content\" href=\"#fs-idm184565904\">(Table 4.6.1)<\/a>.<\/p>\r\n\r\n<table id=\"fs-idm184565904\" class=\"aligncenter\" summary=\"This table has two columns and seven rows. The first row is a header row, and it labels each column, \u201cClass,\u201d and, \u201cFunction.\u201d Under the \u201cClass\u201d column are the following: \u201coxidoreductases,\u201d \u201ctransferases,\u201d \u201chydrolases,\u201d \u201clyases,\u201d \u201cisomerases,\u201d and \u201cligases.\u201d Under the \u201cFunction\u201d column are the following: \u201credox reactions,\u201d \u201ctransfer of functional groups,\u201d \u201chydrolysis reactions,\u201d \u201cgroup elimination to form double bonds,\u201d \u201cisomerization,\u201d and \u201cbond formation with ATP hydrolysis.\u201d\"><caption><strong>Table 4.6.1 - <\/strong>Classes of Enzymes and Their Functions<\/caption>\r\n<thead>\r\n<tr valign=\"middle\">\r\n<th data-align=\"left\">Class<\/th>\r\n<th data-align=\"left\">Function<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">oxidoreductases<\/td>\r\n<td data-align=\"left\">redox reactions<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">transferases<\/td>\r\n<td data-align=\"left\">transfer of functional groups<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">hydrolases<\/td>\r\n<td data-align=\"left\">hydrolysis reactions<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">lyases<\/td>\r\n<td data-align=\"left\">group elimination to form double bonds<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">isomerases<\/td>\r\n<td data-align=\"left\">isomerization<\/td>\r\n<\/tr>\r\n<tr valign=\"middle\">\r\n<td data-align=\"left\">ligases<\/td>\r\n<td data-align=\"left\">bond formation with ATP hydrolysis<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-idm189720768\">Enzyme molecules possess an active site, a part of the molecule with a shape that allows it to bond to a specific substrate (a reactant molecule), forming an enzyme-substrate complex as a reaction intermediate. There are two models that attempt to explain how this active site works. The most simplistic model is referred to as the lock-and-key hypothesis, which suggests that the molecular shapes of the active site and substrate are complementary, fitting together like a key in a lock. The induced fit hypothesis, on the other hand, suggests that the enzyme molecule is flexible and changes shape to accommodate a bond with the substrate. This is not to suggest that an enzyme\u2019s active site is completely malleable, however. Both the lock-and-key model and the induced fit model account for the fact that enzymes can only bind with specific substrates, since in general a particular enzyme only catalyzes a particular reaction <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Enzyme\">(Figure 4.6.7)<\/a>.<\/p>\r\n\r\n<div id=\"CNX_Chem_12_07_Enzyme\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\"><em>\u00a0<\/em><\/div>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Enzyme-1.jpg\" alt=\"A diagram is shown of two possible interactions of an enzyme and a substrate. In a, which is labeled \u201cLock-and-key,\u201d two diagrams are shown. The first shows a green wedge-like shape with two small depressions in the upper surface of similar size, but the depression on the left has a curved shape, and the depression on the right has a pointed shape. This green shape is labeled \u201cEnzyme.\u201d Just above this shape are two smaller, irregular, lavender shapes each with a projection from its lower surface. The lavender shape on the left has a curved projection which matches the shape of the depression on the left in the green shape below. This projection is shaded orange and has a curved arrow extending from in to the matching depression in the green shape below. Similarly, the lavender shape on the right has a projection with a pointed tip which matches the shape of the depression on the right in the green shape below. This projection is shaded orange and has a curved arrow extending from in to the matching depression in the green shape below. Two line segments extend from the depressions in the green shape to form an inverted V shape above the depressions. Above this and between the lavender shapes is the label, \u201cActive site is proper shape.\u201d The label \u201cSubstrates\u201d is at the very top of the diagram with line segments extending to the two lavender shapes. To the right of this diagram is a second diagram showing the lavender shapes positioned next to each other, fit snugly into the depressions in the green shape, which is labeled \u201cEnzyme.\u201d Above this diagram is the label, \u201cSubstrate complex formed.\u201d In b, which is labeled \u201cInduced fit,\u201d two diagrams are shown. The first shows a green wedge-like shape with two small depressions in the upper surface of similar size, but irregular shape. This green shape is labeled \u201cEnzyme.\u201d Just above this shape are two smaller irregular lavender shapes each with a projection from its lower surface. The lavender shape on the left has a curved projection. This projection is shaded orange and has a curved arrow extending from it to the irregular depression just below it in the green shape below. Similarly, the lavender shape on the right has a projection with a pointed tip. This projection is shaded orange and has a curved arrow extending from it to the irregular depression just below it in the green shape below. Two line segments extend from the depressions in the green shape to form an inverted V shape above the depressions. Above this and between the lavender shapes is the label, \u201cActive site changes to fit.\u201d The label, \u201cSubstrates\u201d is at the very top of the diagram with line segments extending to the two lavender shapes. To the right of this diagram is a second diagram showing the purple shapes positioned next to each other, fit snugly into the depressions in the green shape, which is labeled \u201cEnzyme.\u201d Above this diagram is the label \u201cSubstrate complex formed.\u201d The projections from the lavender shapes match the depression shapes in the green shape, resulting in a proper fit.\" width=\"975\" height=\"428\" data-media-type=\"image\/jpeg\" \/> <strong>Figure 4.6.7 - (a) According to the lock-and-key model, the shape of an enzyme\u2019s active site is a perfect fit for the substrate. (b) According to the induced fit model, the active site is somewhat flexible, and can change shape in order to bond with the substrate.<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm145649744\" class=\"chemistry link-to-learning\" data-type=\"note\">\r\n<p id=\"fs-idm187403424\">The <a href=\"http:\/\/openstaxcollege.org\/l\/16enzymes\">Royal Society of Chemistry<\/a> provides an excellent introduction to enzymes for students and teachers.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm181838416\" class=\"summary\" data-depth=\"1\">\r\n<h1 data-type=\"title\">Key Concepts and Summary<\/h1>\r\n<p id=\"fs-idm186233248\">Catalysts affect the rate of a chemical reaction by altering its mechanism to provide a lower activation energy. Catalysts can be homogenous (in the same phase as the reactants) or heterogeneous (a different phase than the reactants).<\/p>\r\n\r\n<\/div>\r\n<strong>Some useful links on heterogeneous catalysis:<\/strong>\r\n<ul>\r\n \t<li><a href=\"https:\/\/cen.acs.org\/articles\/95\/i29\/Hunting-hidden-chemistry-heterogeneous-catalysts.html\">https:\/\/cen.acs.org\/articles\/95\/i29\/Hunting-hidden-chemistry-heterogeneous-catalysts.html<\/a><\/li>\r\n \t<li><a href=\"https:\/\/www.preprints.org\/manuscript\/201901.0175\/v1\">https:\/\/www.preprints.org\/manuscript\/201901.0175\/v1<\/a><\/li>\r\n \t<li><a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.accounts.6b00510\">https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.accounts.6b00510<\/a><\/li>\r\n \t<li><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/9781119951438.eibc0079.pub2\">https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/9781119951438.eibc0079.pub2<\/a><\/li>\r\n \t<li><a href=\"http:\/\/web.uvic.ca\/~mcindoe\/423\/homovshet.pdf\">http:\/\/web.uvic.ca\/~mcindoe\/423\/homovshet.pdf<\/a><\/li>\r\n \t<li><a href=\"https:\/\/www.sciencedaily.com\/releases\/2019\/05\/190528140112.htm\">https:\/\/www.sciencedaily.com\/releases\/2019\/05\/190528140112.htm<\/a><\/li>\r\n \t<li><a href=\"https:\/\/www.degruyter.com\/downloadpdf\/j\/eces.2018.25.issue-1\/eces-2018-0001\/eces-2018-0001.pdf\">https:\/\/www.degruyter.com\/downloadpdf\/j\/eces.2018.25.issue-1\/eces-2018-0001\/eces-2018-0001.pdf<\/a><\/li>\r\n \t<li><a href=\"http:\/\/www.lifesci.sussex.ac.uk\/research\/fluorine\/p5qsp3l\/Teaching\/chem_533\/Catalysis.pdf\">http:\/\/www.lifesci.sussex.ac.uk\/research\/fluorine\/p5qsp3l\/Teaching\/chem_533\/Catalysis.pdf<\/a><\/li>\r\n<\/ul>\r\n<div id=\"fs-idm181838416\" class=\"summary\" data-depth=\"1\">\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">End of Chapter Exercises<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<div id=\"fs-idm121944048\" data-type=\"exercise\">\r\n<div id=\"fs-idm262670608\" data-type=\"problem\">\r\n<p id=\"fs-idm127239504\">(1) Account for the increase in reaction rate brought about by a catalyst.<\/p>\r\n\r\n<\/div>\r\n&nbsp;\r\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\r\n\r\n<div id=\"fs-idm162244848\" style=\"padding-left: 40px\" data-type=\"solution\">\r\n<p id=\"fs-idm276597024\">The general mode of action for a catalyst is to provide a mechanism by which the reactants can unite more readily by taking a path with a lower reaction energy. The rates of both the forward and the reverse reactions are increased, leading to a faster achievement of equilibrium.<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm119808848\" data-type=\"exercise\">\r\n<div id=\"fs-idm209867568\" data-type=\"problem\">\r\n<p id=\"fs-idm221201728\">(2) Compare the functions of homogeneous and heterogeneous catalysts.<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm268031984\" data-type=\"exercise\">\r\n<div id=\"fs-idm121870880\" data-type=\"problem\">\r\n<p id=\"fs-idm224601824\">(3) Consider this scenario and answer the following questions:<\/p>\r\nChlorine atoms resulting from decomposition of chlorofluoromethanes, such as CCl<sub>2<\/sub>F<sub>2<\/sub>, catalyze the decomposition of ozone in the atmosphere. One simplified mechanism for the decomposition is:\r\n\r\n<span data-type=\"newline\">\r\n<\/span> \\(\\begin{array}{}\\\\ \\\\ {\\text{O}}_{3}\\stackrel{\\phantom{\\rule{0.2em}{0ex}}\\text{sunlight}\\phantom{\\rule{0.2em}{0ex}}}{\\to }{\\text{O}}_{2}+\\text{O}\\\\ {\\text{O}}_{3}+\\text{Cl}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{O}}_{2}+\\text{ClO}\\\\ \\text{ClO}+\\text{O}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{Cl}+{\\text{O}}_{2}\\end{array}\\)\r\n\r\n&nbsp;\r\n<p id=\"fs-idm174347728\">(3a) Explain why chlorine atoms are catalysts in the gas-phase transformation:<\/p>\r\n<span data-type=\"newline\">\r\n<\/span> \\(2{\\text{O}}_{3}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}3{\\text{O}}_{2}\\)\r\n<p id=\"fs-idm280039520\">(3b) Nitric oxide is also involved in the decomposition of ozone by the mechanism:<\/p>\r\n<span data-type=\"newline\">\r\n<\/span> \\(\\begin{array}{}\\\\ {\\text{O}}_{3}\\stackrel{\\phantom{\\rule{0.2em}{0ex}}\\text{sunlight}\\phantom{\\rule{0.2em}{0ex}}}{\\to }{\\text{O}}_{2}+\\text{O}\\\\ {\\text{O}}_{3}+\\text{NO}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}{\\text{NO}}_{2}+{\\text{O}}_{2}\\\\ {\\text{NO}}_{2}+\\text{O}\\phantom{\\rule{0.2em}{0ex}}$\\rightarrow$\\phantom{\\rule{0.2em}{0ex}}\\text{NO}+{\\text{O}}_{2}\\end{array}\\)\r\n<p id=\"fs-idm271887104\">Is NO a catalyst for the decomposition? Explain your answer.<\/p>\r\n\r\n<\/div>\r\n&nbsp;\r\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\r\n\r\n<div id=\"fs-idm242301568\" style=\"padding-left: 40px\" data-type=\"solution\">\r\n<p id=\"fs-idm226654304\">(a) Chlorine atoms are a catalyst because they react in the second step but are regenerated in the third step. Thus, they are not used up, which is a characteristic of catalysts. (b) NO is a catalyst for the same reason as in part (a).<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm194307024\" data-type=\"exercise\">\r\n<div id=\"fs-idm126642096\" data-type=\"problem\">\r\n<p id=\"fs-idm279414832\">(4) For each of the following pairs of reaction diagrams, identify which of the pair is catalyzed:<\/p>\r\n<p id=\"fs-idm3297152\">(4a)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm228138944\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axis of the first graph is marked off from 0 to 30 in intervals of 5. The y-axis of the second graph is marked off from 0 to 25 by intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 12. The curve then rises sharply near the middle to reach a maximum of about 24 and similarly falls to another horizontal segment at 5. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise4a_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axis of the first graph is marked off from 0 to 30 in intervals of 5. The y-axis of the second graph is marked off from 0 to 25 by intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 12. The curve then rises sharply near the middle to reach a maximum of about 24 and similarly falls to another horizontal segment at 5. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idm188080944\">(4b)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm190586416\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy.\u201d The y-axes are marked off from 0 to 50 in intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 2. The curve then rises sharply near the middle to reach a maximum of about 43 and similarly falls to another horizontal segment at 15. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only about 32.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise4b_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy.\u201d The y-axes are marked off from 0 to 50 in intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 2. The curve then rises sharply near the middle to reach a maximum of about 43 and similarly falls to another horizontal segment at 15. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only about 32.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm219276192\" data-type=\"exercise\">\r\n\r\n&nbsp;\r\n<div id=\"fs-idm152746480\" data-type=\"problem\">\r\n\r\n&nbsp;\r\n<p id=\"fs-idm178760704\">(5) For each of the following pairs of reaction diagrams, identify which of the pairs is catalyzed:<\/p>\r\n<p id=\"fs-idm338845344\">(5a)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm241665200\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 2J. The curve then rises sharply near the middle to reach a maximum of about 46, then sharply falls to about 35, again rises to about 38 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 46, drops to about 35, then rises to about 43 before falling to the horizontal region at about 15.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise5a_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 2J. The curve then rises sharply near the middle to reach a maximum of about 46, then sharply falls to about 35, again rises to about 38 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 46, drops to about 35, then rises to about 43 before falling to the horizontal region at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idm210073232\">(5b)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm274120656\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 34. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 25, again rises sharply to about 35 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 40, drops to 25, then rises to 35 before falling to the horizontal region at about 15.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise5b_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 34. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 25, again rises sharply to about 35 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 40, drops to 25, then rises to 35 before falling to the horizontal region at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<div id=\"fs-idm29928320\" data-type=\"solution\">\r\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\r\n<p id=\"fs-idm222281872\" style=\"padding-left: 40px\">The lowering of the transition state energy indicates the effect of a catalyst. (a) B; (b) B<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm260004768\" data-type=\"exercise\">\r\n<div id=\"fs-idm224432608\" data-type=\"problem\">\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n<p id=\"fs-idm245642464\">(6) For each of the following reaction diagrams, estimate the activation energy (<em data-effect=\"italics\">E<\/em><sub>a<\/sub>) of the reaction:<\/p>\r\n<p id=\"fs-idm211017072\">(6a)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm271936272\" class=\"scaled-down\" data-type=\"media\" data-alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 35 and similarly falls to another horizontal segment at 5.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise6a_img-1.jpg\" alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 35 and similarly falls to another horizontal segment at 5.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idm220847584\">(6b)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm239333712\" class=\"scaled-down\" data-type=\"media\" data-alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 20 and similarly falls to another horizontal segment at 5.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise6b_img-1.jpg\" alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 20 and similarly falls to another horizontal segment at 5.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm218836096\" data-type=\"exercise\">\r\n<div id=\"fs-idm224927248\" data-type=\"problem\">\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n<p id=\"fs-idm159516400\">(7) For each of the following reaction diagrams, estimate the activation energy (<em data-effect=\"italics\">E<\/em><sub>a<\/sub>) of the reaction:<\/p>\r\n<p id=\"fs-idm197289104\">(7a)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm235765824\" class=\"scaled-down\" data-type=\"media\" data-alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 24, again rises to about 30 and falls to another horizontal segment at about 15.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise7a_img-1.jpg\" alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 24, again rises to about 30 and falls to another horizontal segment at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idm290032736\">(7b)<span data-type=\"newline\">\r\n<\/span><\/p>\r\n<span id=\"fs-idm266488640\" class=\"scaled-down\" data-type=\"media\" data-alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 40, again rises to about 45 and falls to another horizontal segment at about 20.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise7b_img-1.jpg\" alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 40, again rises to about 45 and falls to another horizontal segment at about 20.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<div id=\"fs-idm202007568\" data-type=\"solution\">\r\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\r\n<p id=\"fs-idm35117840\" style=\"padding-left: 40px\">The energy needed to go from the initial state to the transition state is (a) 10 kJ; (b) 10 kJ.<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm189363504\" data-type=\"exercise\">\r\n<div id=\"fs-idm152738576\" data-type=\"problem\">\r\n<p id=\"fs-idm252327824\">(8) Assuming the diagrams in Q6 represent different mechanisms for the same reaction, which of the reactions has the faster rate?<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm225889216\" data-type=\"exercise\">\r\n<div id=\"fs-idm209352752\" data-type=\"problem\">\r\n<p id=\"fs-idm286704000\">(9) Consider the similarities and differences in the two reaction diagrams shown in Q7.\u00a0Do these diagrams represent two different overall reactions, or do they represent the same overall reaction taking place by two different mechanisms? Explain your answer.<\/p>\r\n&nbsp;\r\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm241364160\" style=\"padding-left: 40px\" data-type=\"solution\">\r\n<p id=\"fs-idm218832672\">Both diagrams describe two-step, exothermic reactions, but with different changes in enthalpy, suggesting the diagrams depict two different overall reactions.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\" data-type=\"glossary\">\r\n<h2 data-type=\"glossary-title\">Glossary<\/h2>\r\n<dl id=\"fs-idm228167568\">\r\n \t<dt>[pb_glossary id=\"3134\"]heterogeneous catalyst[\/pb_glossary]<\/dt>\r\n \t<dd id=\"fs-idm173613040\">catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm218392224\">\r\n \t<dt>[pb_glossary id=\"3135\"]homogeneous catalyst[\/pb_glossary]<\/dt>\r\n \t<dd id=\"fs-idm192625440\">catalyst present in the same phase as the reactants<\/dd>\r\n<\/dl>\r\n<\/div>","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Learning Objectives<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Explain the function of a catalyst in terms of reaction mechanisms and potential energy diagrams<\/li>\n<li>List examples of catalysis in natural and industrial processes<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p id=\"fs-idm241568976\">Among the factors affecting chemical reaction rates discussed earlier in this chapter was the presence of a <em data-effect=\"italics\">catalyst<\/em>, a substance that can increase the reaction rate without being consumed in the reaction. The concepts introduced in the previous section on reaction mechanisms provide the basis for understanding how catalysts are able to accomplish this very important function.<\/p>\n<p id=\"fs-idm627108512\"><a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_CatReCoDig\">(Figure 4.6.1)<\/a> shows reaction diagrams for a chemical process in the absence and presence of a catalyst. Inspection of the diagrams reveals several traits of these reactions. Consistent with the fact that the two diagrams represent the same overall reaction, both curves begin and end at the same energies (in this case, because products are more energetic than reactants, the reaction is endothermic). The reaction mechanisms, however, are clearly different. The uncatalyzed reaction proceeds via a one-step mechanism (one transition state observed), whereas the catalyzed reaction follows a two-step mechanism (two transition states observed) with <em data-effect=\"italics\">a notably lesser activation energy<\/em>. This difference illustrates the means by which a catalyst functions to accelerate reactions, namely, by providing an alternative reaction mechanism with a lower activation energy. Although the catalyzed reaction mechanism for a reaction needn\u2019t necessarily involve a different number of steps than the uncatalyzed mechanism, it must provide a reaction path whose rate determining step is faster (lower <em data-effect=\"italics\">E<\/em><sub>a<\/sub>).<\/p>\n<div id=\"CNX_Chem_12_07_CatReCoDig\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\"><em>\u00a0\u00a0<\/em><\/div>\n<figure style=\"width: 650px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2019\/07\/CNX_Chem_12_07_CatReCoDig-1-1.jpg\" alt=\"A graph is shown with the label, \u201cExtent of reaction,\u201d appearing in a right pointing arrow below the x-axis and the label, \u201cEnergy,\u201d in an upward pointing arrow just left of the y-axis. Approximately one-fifth of the way up the y-axis, a very short, somewhat flattened portion of both a red and a blue curve are shown. This region is labeled \u201cReactants.\u201d A red concave down curve extends upward to reach a maximum near the height of the y-axis. From the peak, the curve continues downward to a second horizontally flattened region at a height of about one-third the height of the y-axis. This flattened region is labeled, \u201cProducts.\u201d A second curve is drawn in blue with the same flattened regions at the start and end of the curve. The height of this curve is about two-thirds the height of the first curve and just right of its maximum, the curve dips low, then rises back and continues a downward trend at a lower height, but similar to that of the red curve. A horizontal dashed straight line extends from the point where both curves start in the \u201cReactants\u201d region. A double sided arrow extends from the \u201cProducts\u201d region at the end of both curves to this horizontal dashed line. This is labeled \u201ccapital delta H.\u201d A double sided arrow extends from the dashed horizontal line to the peak of the red concave down curve. This arrow is labeled \u201cE subscript a.\u201d Another double sided arrow extends from the dashed horizontal line to the peak of the blue curve. This arrow is labeled \u201cE subscript a.\u201d\" width=\"650\" height=\"567\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.1 &#8211; Reaction diagrams for an endothermic process in the absence (red curve) and presence (blue curve) of a catalyst. The catalyzed pathway involves a two-step mechanism (note the presence of two transition states) and an intermediate species (represented by the valley between the two transitions states).<\/strong><\/figcaption><\/figure>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Activity 4.6.1 &#8211; Reaction Diagrams for Catalyzed Reactions<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>The two reaction diagrams here represent the same reaction: one without a catalyst and one with a catalyst. Estimate the activation energy for each process, and identify which one involves a catalyst.<\/p>\n<p><span id=\"fs-idm142234720\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy ( k J ).\u201d The y-axes are marked off from 0 to 50 in intervals of five. In a, a blue curve is shown. It begins with a horizontal segment at about 6. The curve then rises sharply near the middle to reach a maximum of about 32 and similarly falls to another horizontal segment at about 10. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\"><img decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Rxndiagramex_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy ( k J ).\u201d The y-axes are marked off from 0 to 50 in intervals of five. In a, a blue curve is shown. It begins with a horizontal segment at about 6. The curve then rises sharply near the middle to reach a maximum of about 32 and similarly falls to another horizontal segment at about 10. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<h2 id=\"fs-idm154613456\">Solution<\/h2>\n<p>Activation energies are calculated by subtracting the reactant energy from the transition state energy.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm239782272\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-dcdc73239adbf1a8740773461824003f_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#99;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#100;&#105;&#97;&#103;&#114;&#97;&#109;&#32;&#40;&#97;&#41;&#58;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#69;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#97;&#125;&#125;&#61;&#51;&#50;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#45;&#54;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#61;&#50;&#54;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#92;&#104;&#102;&#105;&#108;&#108;&#32;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#100;&#105;&#97;&#103;&#114;&#97;&#109;&#32;&#40;&#98;&#41;&#58;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#69;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#97;&#125;&#125;&#61;&#50;&#48;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#45;&#54;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#61;&#49;&#52;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#107;&#74;&#125;&#92;&#104;&#102;&#105;&#108;&#108;&#32;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"41\" width=\"301\" style=\"vertical-align: -16px;\" \/><\/div>\n<div data-type=\"equation\"><em>\u00a0\u00a0<\/em><\/div>\n<p id=\"fs-idm202838144\">The catalyzed reaction is the one with lesser activation energy, in this case represented by diagram b.<\/p>\n<h2 id=\"fs-idm163597616\"><span data-type=\"title\">Check Your Learning<\/span><\/h2>\n<p>Reaction diagrams for a chemical process with and without a catalyst are shown below. Both reactions involve a two-step mechanism with a rate-determining first step. Compute activation energies for the first step of each mechanism, and identify which corresponds to the catalyzed reaction. How do the second steps of these two mechanisms compare?<\/p>\n<p><span id=\"fs-idm153634048\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeledc \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 100 at intervals of 10. In a, a blue curve is shown. It begins with a horizontal segment at about 10. The curve then rises sharply near the middle to reach a maximum of about 91, then sharply falls to about 52, again rises sharply to about 73 and falls to another horizontal segment at about 5. In b, the curve begins and ends similarly, but the first peak reaches about 81, drops to about 55, then rises to about 77 before falling to the horizontal region at about 5.\"><img decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Rxndiagramcyl_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeledc \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 100 at intervals of 10. In a, a blue curve is shown. It begins with a horizontal segment at about 10. The curve then rises sharply near the middle to reach a maximum of about 91, then sharply falls to about 52, again rises sharply to about 73 and falls to another horizontal segment at about 5. In b, the curve begins and ends similarly, but the first peak reaches about 81, drops to about 55, then rises to about 77 before falling to the horizontal region at about 5.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<div id=\"fs-idm215189760\" data-type=\"note\">\n<h3 style=\"text-align: right\" data-type=\"title\">Answer<\/h3>\n<p id=\"fs-idm239441760\" style=\"text-align: right\">For the first step, <em data-effect=\"italics\">E<\/em><sub>a<\/sub> = 80 kJ for (a) and 70 kJ for (b), so diagram (b) depicts the catalyzed reaction. Activation energies for the second steps of both mechanisms are the same, 20 kJ.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\n<h2 data-type=\"title\">Homogeneous Catalysts<\/h2>\n<p id=\"fs-idm243256336\">A <span data-type=\"term\">homogeneous catalyst<\/span> is present in the same phase as the reactants. It interacts with a reactant to form an intermediate substance, which then decomposes or reacts with another reactant in one or more steps to regenerate the original catalyst and form product. As an important illustration of homogeneous catalysis, consider the earth\u2019s ozone layer. Ozone in the upper atmosphere, which protects the earth from ultraviolet radiation, is formed when oxygen molecules absorb ultraviolet light and undergo the reaction:<\/p>\n<div id=\"fs-idm276049600\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-9d2d06dd6f858dbd55744432c71d0ce1_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#51;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#115;&#116;&#97;&#99;&#107;&#114;&#101;&#108;&#123;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#55;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#104;&#118;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#55;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#125;&#123;&#92;&#116;&#111;&#32;&#125;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"24\" width=\"161\" style=\"vertical-align: -5px;\" \/><\/div>\n<p id=\"fs-idm291675632\">Ozone is a relatively unstable molecule that decomposes to yield diatomic oxygen by the reverse of this equation. This decomposition reaction is consistent with the following two-step mechanism:<\/p>\n<div id=\"fs-idm37859104\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-b44ad7571cb7cff97fabcd40c49c5c8b_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#125;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"37\" width=\"104\" style=\"vertical-align: -25px;\" \/><\/div>\n<p id=\"fs-idm103646832\">A number of substances can catalyze the decomposition of ozone. For example, the nitric oxide\u2013catalyzed decomposition of ozone is believed to occur via the following three-step mechanism:<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\n<div id=\"fs-idm109392\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-c153e4766a76815ab53b0427781ad6d5_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"63\" width=\"275\" style=\"vertical-align: -38px;\" \/><\/div>\n<\/div>\n<div data-type=\"equation\"><\/div>\n<div data-type=\"equation\"><span style=\"text-align: initial;font-size: 1em\">As required, the overall reaction is the same for both the two-step uncatalyzed mechanism and the three-step NO-catalyzed mechanism:<\/span><\/div>\n<div id=\"fs-idm65053840\" class=\"bc-section section\" data-depth=\"1\">\n<p>&nbsp;<\/p>\n<div id=\"fs-idm46801248\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-83dc60007b72d18ff3983a4c73d2e0fd_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#51;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;\" title=\"Rendered by QuickLaTeX.com\" height=\"19\" width=\"139\" style=\"vertical-align: -5px;\" \/><\/div>\n<p id=\"fs-idm251830192\">Notice that NO is a reactant in the first step of the mechanism and a product in the last step. This is another characteristic trait of a catalyst: Though it participates in the chemical reaction, it is not consumed by the reaction.<\/p>\n<div id=\"fs-idm195911072\" class=\"chemistry chemist-portrait\" data-type=\"note\">\n<h2 data-type=\"title\">Mario J. Molina<\/h2>\n<p id=\"fs-idm149608448\">The 1995 Nobel Prize in Chemistry was shared by Paul J. Crutzen, Mario J. <span class=\"no-emphasis\" data-type=\"term\">Molina<\/span> (<a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Molina\">Figure 4.6.2<\/a>), and F. Sherwood Rowland \u201cfor their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone.\u201d<a class=\"footnote\" title=\"\u201cThe Nobel Prize in Chemistry 1995,\u201d Nobel Prize.org, accessed February 18, 2015, http:\/\/www.nobelprize.org\/nobel_prizes\/chemistry\/laureates\/1995\/\" id=\"return-footnote-2377-1\" href=\"#footnote-2377-1\" aria-label=\"Footnote 1\"><sup class=\"footnote\">[1]<\/sup><\/a> Molina, a Mexican citizen, carried out the majority of his work at the Massachusetts Institute of Technology (MIT).<\/p>\n<div id=\"CNX_Chem_12_07_Molina\" class=\"bc-figure figure\">\n<figure style=\"width: 1200px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Molina-1.jpg\" alt=\"A photograph is shown of Mario Molina. To the right of the photo, an image of Earth\u2019s southern hemisphere is shown with a central circular region in purple with a radius of about half that of the entire hemisphere. Just outside this region is a narrow royal blue band, followed by an outer thin turquoise blue band. The majority of the outermost region is green. Two small bands of yellow are present in the lower regions of the image.\" width=\"1200\" height=\"511\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.2 &#8211; (a) Mexican chemist Mario Molina (1943 \u2013) shared the Nobel Prize in Chemistry in 1995 for his research on (b) the Antarctic ozone hole. (credit a: courtesy of Mario Molina; credit b: modification of work by NASA)<\/strong><\/figcaption><\/figure>\n<\/div>\n<p id=\"fs-idm242073328\">In 1974, Molina and Rowland published a paper in the journal <em data-effect=\"italics\">Nature<\/em> detailing the threat of chlorofluorocarbon gases to the stability of the ozone layer in earth\u2019s upper atmosphere. The ozone layer protects earth from solar radiation by absorbing ultraviolet light. As chemical reactions deplete the amount of ozone in the upper atmosphere, a measurable \u201chole\u201d forms above Antarctica, and an increase in the amount of solar ultraviolet radiation\u2014 strongly linked to the prevalence of skin cancers\u2014reaches earth\u2019s surface. The work of Molina and Rowland was instrumental in the adoption of the Montreal Protocol, an international treaty signed in 1987 that successfully began phasing out production of chemicals linked to ozone destruction.<\/p>\n<p id=\"fs-idm4297296\">Molina and Rowland demonstrated that chlorine atoms from human-made chemicals can catalyze ozone destruction in a process similar to that by which NO accelerates the depletion of ozone. Chlorine atoms are generated when chlorocarbons or chlorofluorocarbons\u2014once widely used as refrigerants and propellants\u2014are photochemically decomposed by ultraviolet light or react with hydroxyl radicals. A sample mechanism is shown here using methyl chloride:<\/p>\n<div id=\"fs-idm241556704\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-3a6e842515449b2d2bc1636c19253eff_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#72;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#72;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#111;&#116;&#104;&#101;&#114;&#32;&#112;&#114;&#111;&#100;&#117;&#99;&#116;&#115;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"16\" width=\"271\" style=\"vertical-align: -4px;\" \/><\/div>\n<p id=\"fs-idm211108656\">Chlorine radicals break down ozone and are regenerated by the following catalytic cycle:<\/p>\n<div id=\"fs-idm150620768\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-379dde7ae90e814b38a2ddb8f115775f_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#79;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#79;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#111;&#118;&#101;&#114;&#97;&#108;&#108;&#32;&#82;&#101;&#97;&#99;&#116;&#105;&#111;&#110;&#58;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"59\" width=\"245\" style=\"vertical-align: -36px;\" \/><\/div>\n<p id=\"fs-idm225343040\">A single monatomic chlorine can break down thousands of ozone molecules. Luckily, the majority of atmospheric chlorine exists as the catalytically inactive forms Cl<sub>2<\/sub> and ClONO<sub>2<\/sub>. Since receiving his portion of the Nobel Prize, Molina has continued his work in atmospheric chemistry at MIT.<\/p>\n<\/div>\n<div id=\"fs-idm220632992\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\n<h2 data-type=\"title\">Glucose-6-Phosphate Dehydrogenase Deficiency<\/h2>\n<p id=\"fs-idm119819152\">Enzymes in the human body act as catalysts for important chemical reactions in cellular metabolism. As such, a deficiency of a particular enzyme can translate to a life-threatening disease. G6PD (glucose-6-phosphate dehydrogenase) deficiency, a genetic condition that results in a shortage of the enzyme glucose-6-phosphate dehydrogenase, is the most common enzyme deficiency in humans. This enzyme, shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Gluc6PhoDe\">(Figure 4.6.3)<\/a>, is the rate-limiting enzyme for the metabolic pathway that supplies NADPH to cells <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_HMPShuntPa\">(Figure 4.6.4)<\/a>.<\/p>\n<div id=\"CNX_Chem_12_07_Gluc6PhoDe\" class=\"scaled-down\">\n<figure style=\"width: 351px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Gluc6PhoDe-1.jpg\" alt=\"A colorful model of the Glucose-6-phosphate dehydrogenase structure is shown. The molecule has two distinct lobes which are filled with spiraled ribbon-like regions of yellow, lavender, blue, silver, green, and pink.\" width=\"351\" height=\"272\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.3 &#8211;\u00a0Glucose-6-phosphate dehydrogenase is a rate-limiting enzyme for the metabolic pathway that supplies NADPH to cells.<\/strong><\/figcaption><\/figure>\n<\/div>\n<p id=\"fs-idm227628064\">A disruption in this pathway can lead to reduced glutathione in red blood cells; once all glutathione is consumed, enzymes and other proteins such as hemoglobin are susceptible to damage. For example, hemoglobin can be metabolized to bilirubin, which leads to jaundice, a condition that can become severe. People who suffer from G6PD deficiency must avoid certain foods and medicines containing chemicals that can trigger damage their glutathione-deficient red blood cells.<\/p>\n<div id=\"CNX_Chem_12_07_HMPShuntPa\" class=\"bc-figure figure\">\n<figure style=\"width: 1200px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_HMPShuntPa-1.jpg\" alt=\"A reaction mechanism is diagrammed in this figure. At the left, the name Glucose is followed by a horizontal, right pointing arrow, labeled, \u201cHexokinase.\u201d Below this arrow and to the left is a yellow star shape labeled, \u201cA T P.\u201d A curved arrow extends from this shape to the right pointing arrow, and down to the right to a small brown oval labeled, \u201cA D P.\u201d To the right of the horizontal arrow is the name Glucose 6 phosphate, which is followed by another horizontal, right pointing arrow which is labeled, \u201cG 6 P D.\u201d A small orange rectangle below and left of this arrow is labeled \u201cN A D P superscript plus.\u201d A curved arrow extends from this shape to the right pointing arrow, and down to the right to a small salmon-colored rectangle labeled \u201cN A P D H.\u201d A curved arrow extends from this shape below and to the left, back to the orange rectangle labeled, \u201cN A D P superscript plus.\u201d Another curved arrow extends from a green oval labeled \u201cG S S G\u201d below the orange rectangle, up to the arrow curving back to the orange rectangle. This last curved arrow continues on to the lower right to a second green oval labeled, \u201cG S H.\u201d The end of this curved arrow is labeled, \u201cGlutathione reductase.\u201d To the right of the rightmost horizontal arrow appears the name 6 phosphogluconate.\" width=\"1200\" height=\"428\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.4 &#8211; In the mechanism for the pentose phosphate pathway, G6PD catalyzes the reaction that regulates NADPH, a co-enzyme that regulates glutathione, an antioxidant that protects red blood cells and other cells from oxidative damage.<\/strong><\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm254642320\" class=\"bc-section section\" data-depth=\"1\">\n<h2 data-type=\"title\">Heterogeneous Catalysts<\/h2>\n<p id=\"fs-idm31937584\">A <span data-type=\"term\">heterogeneous catalyst<\/span> is a catalyst that is present in a different phase (usually a solid) than the reactants. Such catalysts generally function by furnishing an active surface upon which a reaction can occur. Gas and liquid phase reactions catalyzed by heterogeneous catalysts occur on the surface of the catalyst rather than within the gas or liquid phase.<\/p>\n<p id=\"fs-idm52671504\">Heterogeneous catalysis typically involves the following processes:<\/p>\n<ol id=\"fs-idm202987392\" type=\"1\">\n<li>Adsorption of the reactant(s) onto the surface of the catalyst<\/li>\n<li>Activation of the adsorbed reactant(s)<\/li>\n<li>Reaction of the adsorbed reactant(s)<\/li>\n<li>Desorption of product(s) from the surface of the catalyst<\/li>\n<\/ol>\n<p id=\"fs-idm173407040\"><a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_HetCats\">(Figure 4.6.5)<\/a> illustrates the steps of a mechanism for the reaction of compounds containing a carbon\u2013carbon double bond with hydrogen on a nickel catalyst. Nickel is the catalyst used in the hydrogenation of polyunsaturated fats and oils (which contain several carbon\u2013carbon double bonds) to produce saturated fats and oils (which contain only carbon\u2013carbon single bonds).<\/p>\n<p><em>\u00a0\u00a0<\/em><\/p>\n<div id=\"CNX_Chem_12_07_HetCats\" class=\"scaled-down\">\n<figure style=\"width: 975px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_HetCats-1.jpg\" alt=\"In this figure, four diagrams labeled a through d are shown. In each, a green square surface is shown in perspective to provide a three-dimensional appearance. In a, the label \u201cN i surface\u201d is placed above with a line segment extending to the green square. At the lower left and upper right, pairs of white spheres bonded tougher together appear as well as white spheres on the green surface. Black arrows are drawn from each of the white spheres above the surface to the white sphere on the green surface. In b, the white spheres are still present on the green surface. Near the center of this surface is a molecule with two central black spheres with a double bond indicated by two horizontal black rods between them. Above and below to the left and right, a total of four white spheres are connected to the black spheres with white rods. A line segment extends from this structure to the label, \u201cEthylene absorbed on surface breaking pi bonds.\u201d Just above this is a nearly identical structure greyed out with three downward pointing arrows to the black and white structure to indicate downward motion. The label \u201cEthylene\u201d at the top of the diagram is connected to the greyed out structure with a line segment. In c, the diagram is very similar to b except that the greyed out structure and labels are gone and one of the white spheres near the black and white structure in each pair on the green surface is greyed out. Arrows point from the greyed out white spheres to the double bond between the two black spheres. In d, only a single white sphere remains from each pair in the green surface. A curved arrow points from the middle of the green surface to a model above with two central black spheres with a single black rod indicating a single bond between them. Each of the black rods has three small white spheres bonded as indicated by white rods between the black spheres and the small white spheres. The four bonds around each black sphere are evenly distributed about the black spheres.\" width=\"975\" height=\"401\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.5 &#8211; Mechanism for the Ni-catalyzed reaction <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-0facd99b1aa0df04f663ec3afdefe828_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#125;&#125;&#95;&#123;&#50;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#72;&#125;&#125;&#95;&#123;&#52;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#72;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#125;&#125;&#95;&#123;&#50;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#72;&#125;&#125;&#95;&#123;&#54;&#125;&#46;\" title=\"Rendered by QuickLaTeX.com\" height=\"15\" width=\"154\" style=\"vertical-align: -3px;\" \/> (a) Hydrogen is adsorbed on the surface, breaking the H\u2013H bonds and forming Ni\u2013H bonds. (b) Ethylene is adsorbed on the surface, breaking the C\u2013C \u03c0-bond and forming Ni\u2013C bonds. (c) Atoms diffuse across the surface and form new C\u2013H bonds when they collide. (d) C<sub>2<\/sub>H<sub>6<\/sub> molecules desorb from the Ni surface.<\/strong><\/figcaption><\/figure>\n<\/div>\n<p id=\"fs-idm108887776\">Many important chemical products are prepared via industrial processes that use heterogeneous catalysts, including ammonia, nitric acid, sulfuric acid, and methanol. Heterogeneous catalysts are also used in the catalytic converters found on most gasoline-powered automobiles <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_CatConvert\">(Figure 4.6.6)<\/a>.<\/p>\n<h2><span style=\"font-family: 'Cormorant Garamond', serif;font-size: 1.602em\">Automobile Catalytic Converters<\/span><\/h2>\n<div id=\"fs-idm214293568\" class=\"chemistry everyday-life\" data-type=\"note\">\n<p id=\"fs-idm151500176\">Scientists developed catalytic converters to reduce the amount of toxic emissions produced by burning gasoline in internal combustion engines. By utilizing a carefully selected blend of catalytically active metals, it is possible to effect complete combustion of all carbon-containing compounds to carbon dioxide while also reducing the output of nitrogen oxides. This is particularly impressive when we consider that one step involves adding more oxygen to the molecule and the other involves removing the oxygen.<\/p>\n<div id=\"CNX_Chem_12_07_CatConvert\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\"><em>\u00a0 \u00a0<\/em><\/div>\n<figure style=\"width: 877px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_CatConvert-1.jpg\" alt=\"An image is shown of a catalytic converter. At the upper left, a blue arrow pointing into a pipe that enters a larger, widened chamber is labeled, \u201cDirty emissions.\u201d A small black arrow that points to the lower right is positioned along the upper left side of the widened region. This arrow is labeled, \u201cAdditional oxygen from air pump.\u201d The image shows the converter with the upper surface removed, exposing a red-brown interior. The portion of the converter closest to the dirty emissions inlet shows small, round components in an interior layer. This layer is labeled \u201cThree-way reduction catalyst.\u201d The middle region shows closely packed small brown rods that are aligned parallel to the dirty emissions inlet pipe. The final quarter of the interior of the catalytic converter again shows a layer of closely packed small red brown circles. Two large light grey arrows extend from this layer to the open region at the lower right of the image to the label \u201cClean emissions.\u201d\" width=\"877\" height=\"533\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.6 &#8211; A catalytic converter allows for the combustion of all carbon-containing compounds to carbon dioxide, while at the same time reducing the output of nitrogen oxide and other pollutants in emissions from gasoline-burning engines.<\/strong><\/figcaption><\/figure>\n<\/div>\n<p id=\"fs-idm247003792\">Most modern, three-way catalytic converters possess a surface impregnated with a platinum-rhodium catalyst, which catalyzes the conversion of nitric oxide into dinitrogen and oxygen as well as the conversion of carbon monoxide and hydrocarbons such as octane into carbon dioxide and water vapor:<\/p>\n<p><em>\u00a0\u00a0<\/em><\/p>\n<div id=\"fs-idm216459392\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-6124fb2d7929af7e4054816fe3156791_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#108;&#125;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#92;&#32;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#79;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#79;&#125;&#125;&#95;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#50;&#125;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#92;&#32;&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#125;&#125;&#95;&#123;&#56;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#72;&#125;&#125;&#95;&#123;&#49;&#56;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#50;&#53;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#49;&#54;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#43;&#49;&#56;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#72;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#108;&#101;&#102;&#116;&#40;&#103;&#92;&#114;&#105;&#103;&#104;&#116;&#41;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"63\" width=\"375\" style=\"vertical-align: -27px;\" \/><\/div>\n<div data-type=\"equation\"><em>\u00a0\u00a0<\/em><\/div>\n<p id=\"fs-idm228107536\">In order to be as efficient as possible, most catalytic converters are preheated by an electric heater. This ensures that the metals in the catalyst are fully active even before the automobile exhaust is hot enough to maintain appropriate reaction temperatures.<\/p>\n<\/div>\n<div id=\"fs-idm194237936\" class=\"chemistry link-to-learning\" data-type=\"note\">\n<p id=\"fs-idm266375520\">The University of California at Davis\u2019 \u201cChemWiki\u201d provides a <a href=\"http:\/\/openstaxcollege.org\/l\/16catconvert\">thorough explanation<\/a> of how catalytic converters work.<\/p>\n<\/div>\n<div id=\"fs-idm26203536\" class=\"chemistry sciences-interconnect\" data-type=\"note\">\n<h2 data-type=\"title\">Enzyme Structure and Function<\/h2>\n<p id=\"fs-idm220395040\">The study of enzymes is an important interconnection between biology and chemistry. Enzymes are usually proteins (polypeptides) that help to control the rate of chemical reactions between biologically important compounds, particularly those that are involved in cellular metabolism. Different classes of enzymes perform a variety of functions, as shown in <a class=\"autogenerated-content\" href=\"#fs-idm184565904\">(Table 4.6.1)<\/a>.<\/p>\n<table id=\"fs-idm184565904\" class=\"aligncenter\" summary=\"This table has two columns and seven rows. The first row is a header row, and it labels each column, \u201cClass,\u201d and, \u201cFunction.\u201d Under the \u201cClass\u201d column are the following: \u201coxidoreductases,\u201d \u201ctransferases,\u201d \u201chydrolases,\u201d \u201clyases,\u201d \u201cisomerases,\u201d and \u201cligases.\u201d Under the \u201cFunction\u201d column are the following: \u201credox reactions,\u201d \u201ctransfer of functional groups,\u201d \u201chydrolysis reactions,\u201d \u201cgroup elimination to form double bonds,\u201d \u201cisomerization,\u201d and \u201cbond formation with ATP hydrolysis.\u201d\">\n<caption><strong>Table 4.6.1 &#8211; <\/strong>Classes of Enzymes and Their Functions<\/caption>\n<thead>\n<tr valign=\"middle\">\n<th data-align=\"left\">Class<\/th>\n<th data-align=\"left\">Function<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr valign=\"middle\">\n<td data-align=\"left\">oxidoreductases<\/td>\n<td data-align=\"left\">redox reactions<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"left\">transferases<\/td>\n<td data-align=\"left\">transfer of functional groups<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"left\">hydrolases<\/td>\n<td data-align=\"left\">hydrolysis reactions<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"left\">lyases<\/td>\n<td data-align=\"left\">group elimination to form double bonds<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"left\">isomerases<\/td>\n<td data-align=\"left\">isomerization<\/td>\n<\/tr>\n<tr valign=\"middle\">\n<td data-align=\"left\">ligases<\/td>\n<td data-align=\"left\">bond formation with ATP hydrolysis<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-idm189720768\">Enzyme molecules possess an active site, a part of the molecule with a shape that allows it to bond to a specific substrate (a reactant molecule), forming an enzyme-substrate complex as a reaction intermediate. There are two models that attempt to explain how this active site works. The most simplistic model is referred to as the lock-and-key hypothesis, which suggests that the molecular shapes of the active site and substrate are complementary, fitting together like a key in a lock. The induced fit hypothesis, on the other hand, suggests that the enzyme molecule is flexible and changes shape to accommodate a bond with the substrate. This is not to suggest that an enzyme\u2019s active site is completely malleable, however. Both the lock-and-key model and the induced fit model account for the fact that enzymes can only bind with specific substrates, since in general a particular enzyme only catalyzes a particular reaction <a class=\"autogenerated-content\" href=\"#CNX_Chem_12_07_Enzyme\">(Figure 4.6.7)<\/a>.<\/p>\n<div id=\"CNX_Chem_12_07_Enzyme\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\"><em>\u00a0<\/em><\/div>\n<figure style=\"width: 975px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Enzyme-1.jpg\" alt=\"A diagram is shown of two possible interactions of an enzyme and a substrate. In a, which is labeled \u201cLock-and-key,\u201d two diagrams are shown. The first shows a green wedge-like shape with two small depressions in the upper surface of similar size, but the depression on the left has a curved shape, and the depression on the right has a pointed shape. This green shape is labeled \u201cEnzyme.\u201d Just above this shape are two smaller, irregular, lavender shapes each with a projection from its lower surface. The lavender shape on the left has a curved projection which matches the shape of the depression on the left in the green shape below. This projection is shaded orange and has a curved arrow extending from in to the matching depression in the green shape below. Similarly, the lavender shape on the right has a projection with a pointed tip which matches the shape of the depression on the right in the green shape below. This projection is shaded orange and has a curved arrow extending from in to the matching depression in the green shape below. Two line segments extend from the depressions in the green shape to form an inverted V shape above the depressions. Above this and between the lavender shapes is the label, \u201cActive site is proper shape.\u201d The label \u201cSubstrates\u201d is at the very top of the diagram with line segments extending to the two lavender shapes. To the right of this diagram is a second diagram showing the lavender shapes positioned next to each other, fit snugly into the depressions in the green shape, which is labeled \u201cEnzyme.\u201d Above this diagram is the label, \u201cSubstrate complex formed.\u201d In b, which is labeled \u201cInduced fit,\u201d two diagrams are shown. The first shows a green wedge-like shape with two small depressions in the upper surface of similar size, but irregular shape. This green shape is labeled \u201cEnzyme.\u201d Just above this shape are two smaller irregular lavender shapes each with a projection from its lower surface. The lavender shape on the left has a curved projection. This projection is shaded orange and has a curved arrow extending from it to the irregular depression just below it in the green shape below. Similarly, the lavender shape on the right has a projection with a pointed tip. This projection is shaded orange and has a curved arrow extending from it to the irregular depression just below it in the green shape below. Two line segments extend from the depressions in the green shape to form an inverted V shape above the depressions. Above this and between the lavender shapes is the label, \u201cActive site changes to fit.\u201d The label, \u201cSubstrates\u201d is at the very top of the diagram with line segments extending to the two lavender shapes. To the right of this diagram is a second diagram showing the purple shapes positioned next to each other, fit snugly into the depressions in the green shape, which is labeled \u201cEnzyme.\u201d Above this diagram is the label \u201cSubstrate complex formed.\u201d The projections from the lavender shapes match the depression shapes in the green shape, resulting in a proper fit.\" width=\"975\" height=\"428\" data-media-type=\"image\/jpeg\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4.6.7 &#8211; (a) According to the lock-and-key model, the shape of an enzyme\u2019s active site is a perfect fit for the substrate. (b) According to the induced fit model, the active site is somewhat flexible, and can change shape in order to bond with the substrate.<\/strong><\/figcaption><\/figure>\n<\/div>\n<\/div>\n<div id=\"fs-idm145649744\" class=\"chemistry link-to-learning\" data-type=\"note\">\n<p id=\"fs-idm187403424\">The <a href=\"http:\/\/openstaxcollege.org\/l\/16enzymes\">Royal Society of Chemistry<\/a> provides an excellent introduction to enzymes for students and teachers.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm181838416\" class=\"summary\" data-depth=\"1\">\n<h1 data-type=\"title\">Key Concepts and Summary<\/h1>\n<p id=\"fs-idm186233248\">Catalysts affect the rate of a chemical reaction by altering its mechanism to provide a lower activation energy. Catalysts can be homogenous (in the same phase as the reactants) or heterogeneous (a different phase than the reactants).<\/p>\n<\/div>\n<p><strong>Some useful links on heterogeneous catalysis:<\/strong><\/p>\n<ul>\n<li><a href=\"https:\/\/cen.acs.org\/articles\/95\/i29\/Hunting-hidden-chemistry-heterogeneous-catalysts.html\">https:\/\/cen.acs.org\/articles\/95\/i29\/Hunting-hidden-chemistry-heterogeneous-catalysts.html<\/a><\/li>\n<li><a href=\"https:\/\/www.preprints.org\/manuscript\/201901.0175\/v1\">https:\/\/www.preprints.org\/manuscript\/201901.0175\/v1<\/a><\/li>\n<li><a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.accounts.6b00510\">https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.accounts.6b00510<\/a><\/li>\n<li><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/9781119951438.eibc0079.pub2\">https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/9781119951438.eibc0079.pub2<\/a><\/li>\n<li><a href=\"http:\/\/web.uvic.ca\/~mcindoe\/423\/homovshet.pdf\">http:\/\/web.uvic.ca\/~mcindoe\/423\/homovshet.pdf<\/a><\/li>\n<li><a href=\"https:\/\/www.sciencedaily.com\/releases\/2019\/05\/190528140112.htm\">https:\/\/www.sciencedaily.com\/releases\/2019\/05\/190528140112.htm<\/a><\/li>\n<li><a href=\"https:\/\/www.degruyter.com\/downloadpdf\/j\/eces.2018.25.issue-1\/eces-2018-0001\/eces-2018-0001.pdf\">https:\/\/www.degruyter.com\/downloadpdf\/j\/eces.2018.25.issue-1\/eces-2018-0001\/eces-2018-0001.pdf<\/a><\/li>\n<li><a href=\"http:\/\/www.lifesci.sussex.ac.uk\/research\/fluorine\/p5qsp3l\/Teaching\/chem_533\/Catalysis.pdf\">http:\/\/www.lifesci.sussex.ac.uk\/research\/fluorine\/p5qsp3l\/Teaching\/chem_533\/Catalysis.pdf<\/a><\/li>\n<\/ul>\n<div id=\"fs-idm181838416\" class=\"summary\" data-depth=\"1\">\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">End of Chapter Exercises<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<div id=\"fs-idm121944048\" data-type=\"exercise\">\n<div id=\"fs-idm262670608\" data-type=\"problem\">\n<p id=\"fs-idm127239504\">(1) Account for the increase in reaction rate brought about by a catalyst.<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\n<div id=\"fs-idm162244848\" style=\"padding-left: 40px\" data-type=\"solution\">\n<p id=\"fs-idm276597024\">The general mode of action for a catalyst is to provide a mechanism by which the reactants can unite more readily by taking a path with a lower reaction energy. The rates of both the forward and the reverse reactions are increased, leading to a faster achievement of equilibrium.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm119808848\" data-type=\"exercise\">\n<div id=\"fs-idm209867568\" data-type=\"problem\">\n<p id=\"fs-idm221201728\">(2) Compare the functions of homogeneous and heterogeneous catalysts.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm268031984\" data-type=\"exercise\">\n<div id=\"fs-idm121870880\" data-type=\"problem\">\n<p id=\"fs-idm224601824\">(3) Consider this scenario and answer the following questions:<\/p>\n<p>Chlorine atoms resulting from decomposition of chlorofluoromethanes, such as CCl<sub>2<\/sub>F<sub>2<\/sub>, catalyze the decomposition of ozone in the atmosphere. One simplified mechanism for the decomposition is:<\/p>\n<p><span data-type=\"newline\"><br \/>\n<\/span> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-346f20aeb29d539b7ce588d14860f852_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#125;&#92;&#92;&#32;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#115;&#116;&#97;&#99;&#107;&#114;&#101;&#108;&#123;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#115;&#117;&#110;&#108;&#105;&#103;&#104;&#116;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#125;&#123;&#92;&#116;&#111;&#32;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#79;&#125;&#92;&#92;&#32;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#79;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#67;&#108;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"67\" width=\"160\" style=\"vertical-align: -50px;\" \/><\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm174347728\">(3a) Explain why chlorine atoms are catalysts in the gas-phase transformation:<\/p>\n<p><span data-type=\"newline\"><br \/>\n<\/span> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-95ef20baf97517975ed370f15fb08884_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#50;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#51;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"15\" width=\"85\" style=\"vertical-align: -3px;\" \/><\/p>\n<p id=\"fs-idm280039520\">(3b) Nitric oxide is also involved in the decomposition of ozone by the mechanism:<\/p>\n<p><span data-type=\"newline\"><br \/>\n<\/span> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/ql-cache\/quicklatex.com-5bb062f8afd3d8af04cb50b2eba92168_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#92;&#98;&#101;&#103;&#105;&#110;&#123;&#97;&#114;&#114;&#97;&#121;&#125;&#123;&#125;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#92;&#115;&#116;&#97;&#99;&#107;&#114;&#101;&#108;&#123;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#115;&#117;&#110;&#108;&#105;&#103;&#104;&#116;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#125;&#123;&#92;&#116;&#111;&#32;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#51;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#92;&#32;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#43;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#36;&#92;&#114;&#105;&#103;&#104;&#116;&#97;&#114;&#114;&#111;&#119;&#36;&#92;&#112;&#104;&#97;&#110;&#116;&#111;&#109;&#123;&#92;&#114;&#117;&#108;&#101;&#123;&#48;&#46;&#50;&#101;&#109;&#125;&#123;&#48;&#101;&#120;&#125;&#125;&#92;&#116;&#101;&#120;&#116;&#123;&#78;&#79;&#125;&#43;&#123;&#92;&#116;&#101;&#120;&#116;&#123;&#79;&#125;&#125;&#95;&#123;&#50;&#125;&#92;&#101;&#110;&#100;&#123;&#97;&#114;&#114;&#97;&#121;&#125;\" title=\"Rendered by QuickLaTeX.com\" height=\"67\" width=\"172\" style=\"vertical-align: -39px;\" \/><\/p>\n<p id=\"fs-idm271887104\">Is NO a catalyst for the decomposition? Explain your answer.<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\n<div id=\"fs-idm242301568\" style=\"padding-left: 40px\" data-type=\"solution\">\n<p id=\"fs-idm226654304\">(a) Chlorine atoms are a catalyst because they react in the second step but are regenerated in the third step. Thus, they are not used up, which is a characteristic of catalysts. (b) NO is a catalyst for the same reason as in part (a).<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm194307024\" data-type=\"exercise\">\n<div id=\"fs-idm126642096\" data-type=\"problem\">\n<p id=\"fs-idm279414832\">(4) For each of the following pairs of reaction diagrams, identify which of the pair is catalyzed:<\/p>\n<p id=\"fs-idm3297152\">(4a)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm228138944\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axis of the first graph is marked off from 0 to 30 in intervals of 5. The y-axis of the second graph is marked off from 0 to 25 by intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 12. The curve then rises sharply near the middle to reach a maximum of about 24 and similarly falls to another horizontal segment at 5. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise4a_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axis of the first graph is marked off from 0 to 30 in intervals of 5. The y-axis of the second graph is marked off from 0 to 25 by intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 12. The curve then rises sharply near the middle to reach a maximum of about 24 and similarly falls to another horizontal segment at 5. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only 20.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idm188080944\">(4b)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm190586416\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy.\u201d The y-axes are marked off from 0 to 50 in intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 2. The curve then rises sharply near the middle to reach a maximum of about 43 and similarly falls to another horizontal segment at 15. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only about 32.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise4b_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy.\u201d The y-axes are marked off from 0 to 50 in intervals of 5. In a, a blue curve is shown. It begins with a horizontal region at about 2. The curve then rises sharply near the middle to reach a maximum of about 43 and similarly falls to another horizontal segment at 15. In b, the curve begins and ends similarly, but the maximum reached near the center of the graph is only about 32.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm219276192\" data-type=\"exercise\">\n<p>&nbsp;<\/p>\n<div id=\"fs-idm152746480\" data-type=\"problem\">\n<p>&nbsp;<\/p>\n<p id=\"fs-idm178760704\">(5) For each of the following pairs of reaction diagrams, identify which of the pairs is catalyzed:<\/p>\n<p id=\"fs-idm338845344\">(5a)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm241665200\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 2J. The curve then rises sharply near the middle to reach a maximum of about 46, then sharply falls to about 35, again rises to about 38 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 46, drops to about 35, then rises to about 43 before falling to the horizontal region at about 15.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise5a_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 2J. The curve then rises sharply near the middle to reach a maximum of about 46, then sharply falls to about 35, again rises to about 38 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 46, drops to about 35, then rises to about 43 before falling to the horizontal region at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idm210073232\">(5b)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm274120656\" data-type=\"media\" data-alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 34. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 25, again rises sharply to about 35 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 40, drops to 25, then rises to 35 before falling to the horizontal region at about 15.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise5b_img-1.jpg\" alt=\"In this figure, two graphs are shown. The x-axes are labeled, \u201cExtent of reaction,\u201d and the y-axes are labeled, \u201cEnergy (k J).\u201d The y-axes are marked off from 0 to 50 at intervals of 5. In a, a blue curve is shown. It begins with a horizontal segment at about 34. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 25, again rises sharply to about 35 and falls to another horizontal segment at about 15. In b, the curve begins and ends similarly, but the first peak reaches about 40, drops to 25, then rises to 35 before falling to the horizontal region at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<div id=\"fs-idm29928320\" data-type=\"solution\">\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\n<p id=\"fs-idm222281872\" style=\"padding-left: 40px\">The lowering of the transition state energy indicates the effect of a catalyst. (a) B; (b) B<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm260004768\" data-type=\"exercise\">\n<div id=\"fs-idm224432608\" data-type=\"problem\">\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm245642464\">(6) For each of the following reaction diagrams, estimate the activation energy (<em data-effect=\"italics\">E<\/em><sub>a<\/sub>) of the reaction:<\/p>\n<p id=\"fs-idm211017072\">(6a)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm271936272\" class=\"scaled-down\" data-type=\"media\" data-alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 35 and similarly falls to another horizontal segment at 5.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise6a_img-1.jpg\" alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 35 and similarly falls to another horizontal segment at 5.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idm220847584\">(6b)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm239333712\" class=\"scaled-down\" data-type=\"media\" data-alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 20 and similarly falls to another horizontal segment at 5.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise6b_img-1.jpg\" alt=\"This figure shows a graph. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d The y-axis is marked off from 0 to 40 at intervals of 5. A blue curve is shown. It begins with a horizontal region at 10. The curve then rises sharply near the middle to reach a maximum of 20 and similarly falls to another horizontal segment at 5.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm218836096\" data-type=\"exercise\">\n<div id=\"fs-idm224927248\" data-type=\"problem\">\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p id=\"fs-idm159516400\">(7) For each of the following reaction diagrams, estimate the activation energy (<em data-effect=\"italics\">E<\/em><sub>a<\/sub>) of the reaction:<\/p>\n<p id=\"fs-idm197289104\">(7a)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm235765824\" class=\"scaled-down\" data-type=\"media\" data-alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 24, again rises to about 30 and falls to another horizontal segment at about 15.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise7a_img-1.jpg\" alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 24, again rises to about 30 and falls to another horizontal segment at about 15.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idm290032736\">(7b)<span data-type=\"newline\"><br \/>\n<\/span><\/p>\n<p><span id=\"fs-idm266488640\" class=\"scaled-down\" data-type=\"media\" data-alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 40, again rises to about 45 and falls to another horizontal segment at about 20.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-content\/uploads\/sites\/989\/2020\/06\/CNX_Chem_12_07_Exercise7b_img-1.jpg\" alt=\"In this figure, a graph is shown. The x-axis is labeled, \u201cExtent of reaction,\u201d and the y-axis is labeled, \u201cEnergy (k J).\u201d A blue curve is shown. It begins with a horizontal segment at about 35. The curve then rises sharply near the middle to reach a maximum of about 45, then sharply falls to about 40, again rises to about 45 and falls to another horizontal segment at about 20.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<div id=\"fs-idm202007568\" data-type=\"solution\">\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\n<p id=\"fs-idm35117840\" style=\"padding-left: 40px\">The energy needed to go from the initial state to the transition state is (a) 10 kJ; (b) 10 kJ.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm189363504\" data-type=\"exercise\">\n<div id=\"fs-idm152738576\" data-type=\"problem\">\n<p id=\"fs-idm252327824\">(8) Assuming the diagrams in Q6 represent different mechanisms for the same reaction, which of the reactions has the faster rate?<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm225889216\" data-type=\"exercise\">\n<div id=\"fs-idm209352752\" data-type=\"problem\">\n<p id=\"fs-idm286704000\">(9) Consider the similarities and differences in the two reaction diagrams shown in Q7.\u00a0Do these diagrams represent two different overall reactions, or do they represent the same overall reaction taking place by two different mechanisms? Explain your answer.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"padding-left: 40px\"><em>Solution<\/em><\/p>\n<\/div>\n<div id=\"fs-idm241364160\" style=\"padding-left: 40px\" data-type=\"solution\">\n<p id=\"fs-idm218832672\">Both diagrams describe two-step, exothermic reactions, but with different changes in enthalpy, suggesting the diagrams depict two different overall reactions.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\" data-type=\"glossary\">\n<h2 data-type=\"glossary-title\">Glossary<\/h2>\n<dl id=\"fs-idm228167568\">\n<dt><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_2377_3134\">heterogeneous catalyst<\/a><\/dt>\n<dd id=\"fs-idm173613040\">catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur<\/dd>\n<\/dl>\n<dl id=\"fs-idm218392224\">\n<dt><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_2377_3135\">homogeneous catalyst<\/a><\/dt>\n<dd id=\"fs-idm192625440\">catalyst present in the same phase as the reactants<\/dd>\n<\/dl>\n<\/div>\n<hr class=\"before-footnotes clear\" \/><div class=\"footnotes\"><ol><li id=\"footnote-2377-1\">\u201cThe Nobel Prize in Chemistry 1995,\u201d Nobel Prize.org, accessed February 18, 2015, http:\/\/www.nobelprize.org\/nobel_prizes\/chemistry\/laureates\/1995\/ <a href=\"#return-footnote-2377-1\" class=\"return-footnote\" aria-label=\"Return to footnote 1\">&crarr;<\/a><\/li><\/ol><\/div><div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_2377_3134\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_2377_3134\"><div tabindex=\"-1\"><p>catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_2377_3135\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_2377_3135\"><div tabindex=\"-1\"><p>catalyst present in the same phase as the reactants<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":801,"menu_order":6,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["paul-flowers","klaus-theopold","richard-langley","william-r-robinson"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[61,60,62,63],"license":[52],"class_list":["post-2377","chapter","type-chapter","status-publish","hentry","contributor-klaus-theopold","contributor-paul-flowers","contributor-richard-langley","contributor-william-r-robinson","license-cc-by"],"part":2124,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapters\/2377","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/wp\/v2\/users\/801"}],"version-history":[{"count":15,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapters\/2377\/revisions"}],"predecessor-version":[{"id":3567,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapters\/2377\/revisions\/3567"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/parts\/2124"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapters\/2377\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/wp\/v2\/media?parent=2377"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/pressbooks\/v2\/chapter-type?post=2377"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/wp\/v2\/contributor?post=2377"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/inorganicchemistrychem250\/wp-json\/wp\/v2\/license?post=2377"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}