{"id":898,"date":"2021-07-23T09:21:02","date_gmt":"2021-07-23T13:21:02","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/electrolysis\/"},"modified":"2022-06-23T09:26:13","modified_gmt":"2022-06-23T13:26:13","slug":"electrolysis","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/electrolysis\/","title":{"raw":"17.7 Electrolysis","rendered":"17.7 Electrolysis"},"content":{"raw":"&nbsp;\r\n<div class=\"textbox textbox--learning-objectives\">\r\n<h3><strong>Learning Objectives<\/strong><\/h3>\r\nBy the end of this section you will be able to:\r\n<ul>\r\n \t<li>Describe the process of electrolysis<\/li>\r\n \t<li>Compare the operation of electrolytic cells with that of galvanic cells<\/li>\r\n \t<li>Perform stoichiometric calculations for electrolytic processes<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idm133590080\">Electrochemical cells in which spontaneous redox reactions take place (<em data-effect=\"italics\">galvanic cells<\/em>) have been the topic of discussion so far in this chapter. In these cells, <em data-effect=\"italics\">electrical work is done by a redox system on its surroundings<\/em> as electrons produced by the redox reaction are transferred through an external circuit. This final section of the chapter will address an alternative scenario in which <em data-effect=\"italics\">an external circuit does work on a redox system<\/em> by imposing a voltage sufficient to drive an otherwise nonspontaneous reaction, a process known as <strong>electrolysis<\/strong>. A familiar example of electrolysis is recharging a battery, which involves use of an external power source to drive the spontaneous (discharge) cell reaction in the reverse direction, restoring to some extent the composition of the half-cells and the voltage of the battery. Perhaps less familiar is the use of electrolysis in the refinement of metallic ores, the manufacture of commodity chemicals, and the <em data-effect=\"italics\">electroplating<\/em> of metallic coatings on various products (e.g., jewelry, utensils, auto parts). To illustrate the essential concepts of electrolysis, a few specific processes will be considered.<\/p>\r\n\r\n<div id=\"fs-idp7089472\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>The Electrolysis of Molten Sodium Chloride<\/strong><\/h3>\r\n<p id=\"fs-idm157333328\">Metallic sodium, Na, and chlorine gas, Cl<sub>2<\/sub>, are used in numerous applications, and their industrial production relies on the large-scale electrolysis of molten sodium chloride, NaCl(<em data-effect=\"italics\">l<\/em>). The industrial process typically uses a <em data-effect=\"italics\">Downs cell<\/em> similar to the simplified illustration shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_NaCl\">(Figure)<\/a>. The reactions associated with this process are:<\/p>\r\n\r\n<div id=\"fs-idm155730240\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 2Cl<sup>\u2212<\/sup>(<em>l<\/em>) \u27f6 Cl<sub>2<\/sub>(<em>g<\/em>) + 2e<sup>\u2212<\/sup><\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 2 \u00d7 (Na<sup>+<\/sup>(<em>l<\/em>) + e<sup>\u2212<\/sup> \u27f6 Na(<em>l<\/em>))<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2Na<sup>+<\/sup>(<em>l<\/em>) + 2Cl<sup>\u2212<\/sup>(<em>l<\/em>) \u27f6 2Na(<em>l<\/em>) + Cl<sub>2<\/sub>(<em>g<\/em>)<\/div>\r\n<p id=\"fs-idm174200080\">The cell potential for the above process is negative, indicating the reaction as written (decomposition of liquid NaCl) is not spontaneous. To force this reaction, <em data-effect=\"italics\">a positive potential of magnitude greater than the negative cell potential<\/em> must be applied to the cell.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_17_07_NaCl\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Cells of this sort (a cell for the electrolysis of molten sodium chloride) are used in the <em data-effect=\"italics\">Downs process<\/em> for production of sodium and chlorine, and they typically use iron cathodes and carbon anodes.<\/div>\r\n<span id=\"fs-idm121873696\" data-type=\"media\" data-alt=\"This diagram shows a tank containing a light blue liquid, labeled \u201cMolten N a C l.\u201d A vertical dark grey divider with small, evenly distributed dark dots, labeled \u201cPorous screen\u201d is located at the center of the tank dividing it into two halves. Dark grey bars are positioned at the center of each of the halves of the tank. The bar on the left, which is labeled \u201cAnode\u201d has green bubbles originating from it. The bar on the right which is labeled \u201cCathode\u201d has light grey bubbles originating from it. An arrow points left from the center of the tank toward the anode, which is labeled \u201cC l superscript negative.\u201d An arrow points right from the center of the tank toward the cathode, which is labeled \u201cN a superscript plus.\u201d A line extends from the tops of the anode and cathode to a rectangle centrally placed above the tank which is labeled \u201cVoltage source.\u201d An arrow extends upward above the anode to the left of the line which is labeled \u201ce superscript negative.\u201d A plus symbol is located to the left of the voltage source and a negative sign it located to its right. An arrow points downward along the line segment leading to the cathode. This arrow is labeled \u201ce superscript negative.\u201d The left side of below the diagram is the label \u201c2 C l superscript negative right pointing arrow C l subscript 2 ( g ) plus 2 e superscript negative.\u201d At the right, below the diagram is the label \u201c2 N a superscript plus plus 2 e superscript negative right pointing arrow 2 N a ( l ).\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_NaCl.jpg\" alt=\"This diagram shows a tank containing a light blue liquid, labeled \u201cMolten N a C l.\u201d A vertical dark grey divider with small, evenly distributed dark dots, labeled \u201cPorous screen\u201d is located at the center of the tank dividing it into two halves. Dark grey bars are positioned at the center of each of the halves of the tank. The bar on the left, which is labeled \u201cAnode\u201d has green bubbles originating from it. The bar on the right which is labeled \u201cCathode\u201d has light grey bubbles originating from it. An arrow points left from the center of the tank toward the anode, which is labeled \u201cC l superscript negative.\u201d An arrow points right from the center of the tank toward the cathode, which is labeled \u201cN a superscript plus.\u201d A line extends from the tops of the anode and cathode to a rectangle centrally placed above the tank which is labeled \u201cVoltage source.\u201d An arrow extends upward above the anode to the left of the line which is labeled \u201ce superscript negative.\u201d A plus symbol is located to the left of the voltage source and a negative sign it located to its right. An arrow points downward along the line segment leading to the cathode. This arrow is labeled \u201ce superscript negative.\u201d The left side of below the diagram is the label \u201c2 C l superscript negative right pointing arrow C l subscript 2 ( g ) plus 2 e superscript negative.\u201d At the right, below the diagram is the label \u201c2 N a superscript plus plus 2 e superscript negative right pointing arrow 2 N a ( l ).\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm118223680\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>The Electrolysis of Water<\/strong><\/h3>\r\n<p id=\"fs-idm178403632\">Water may be electrolytically decomposed in a cell similar to the one illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_Water\">(Figure)<\/a>. To improve electrical conductivity without introducing a different redox species, the hydrogen ion concentration of the water is typically increased by addition of a strong acid. The redox processes associated with this cell are<\/p>\r\n\r\n<div id=\"fs-idm33413904\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 O<sub>2<\/sub>(<em>g<\/em>) + 4H<sup>+<\/sup>(<em>aq<\/em>) + 4e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.229 V<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 2 \u00d7(2H<sup>+<\/sup>(<em>aq<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>))\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = 0 V<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 2H<sub>2<\/sub>(<em>g<\/em>) + O<sub>2<\/sub>(g)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cell<\/sub> = \u22121.229 V<\/div>\r\n<p id=\"fs-idp152393360\">Again, the cell potential as written is negative, indicating a nonspontaneous cell reaction that must be driven by imposing a cell voltage greater than +1.229 V. Keep in mind that <em data-effect=\"italics\">standard<\/em> electrode potentials are used to inform thermodynamic predictions here, though the cell is <em data-effect=\"italics\">not<\/em> operating under standard state conditions. Therefore, at best, calculated cell potentials should be considered ballpark estimates.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_17_07_Water\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">The electrolysis of water produces stoichiometric amounts of oxygen gas at the anode and hydrogen at the anode.<\/div>\r\n<span id=\"fs-idm328048\" data-type=\"media\" data-alt=\"This figure shows an apparatus used for electrolysis. A central chamber with an open top has a vertical column extending below that is nearly full of a clear, colorless liquid, which is labeled \u201cH subscript 2 O plus H subscript 2 S O subscript 4.\u201d A horizontal tube in the apparatus connects the central region to vertical columns to the left and right, each of which has a valve or stopcock at the top and a stoppered bottom. On the left, the stopper at the bottom has a small brown square connected just above it in the liquid. The square is labeled \u201cAnode plus.\u201d A black wire extends from the stopper at the left to a rectangle which is labeled \u201cVoltage source\u201d on to the stopper at the right. The left side of the rectangle is labeled with a plus symbol and the right side is labeled with a negative sign. The stopper on the right also has a brown square connected to it which is in the liquid in the apparatus. This square is labeled \u201cCathode negative.\u201d The level of the solution on the left arm or tube of the apparatus is significantly higher than the level of the right arm. Bubbles are present near the surface of the liquid on each side of the apparatus, with the bubbles labeled as \u201cO subscript 2 ( g )\u201d on the left and \u201cH subscript 2 ( g )\u201d on the right.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_Water.jpg\" alt=\"This figure shows an apparatus used for electrolysis. A central chamber with an open top has a vertical column extending below that is nearly full of a clear, colorless liquid, which is labeled \u201cH subscript 2 O plus H subscript 2 S O subscript 4.\u201d A horizontal tube in the apparatus connects the central region to vertical columns to the left and right, each of which has a valve or stopcock at the top and a stoppered bottom. On the left, the stopper at the bottom has a small brown square connected just above it in the liquid. The square is labeled \u201cAnode plus.\u201d A black wire extends from the stopper at the left to a rectangle which is labeled \u201cVoltage source\u201d on to the stopper at the right. The left side of the rectangle is labeled with a plus symbol and the right side is labeled with a negative sign. The stopper on the right also has a brown square connected to it which is in the liquid in the apparatus. This square is labeled \u201cCathode negative.\u201d The level of the solution on the left arm or tube of the apparatus is significantly higher than the level of the right arm. Bubbles are present near the surface of the liquid on each side of the apparatus, with the bubbles labeled as \u201cO subscript 2 ( g )\u201d on the left and \u201cH subscript 2 ( g )\u201d on the right.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm95712768\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>The Electrolysis of Aqueous Sodium Chloride<\/strong><\/h3>\r\n<p id=\"fs-idm37835104\">When aqueous solutions of ionic compounds are electrolyzed, the anode and cathode half-reactions may involve the electrolysis of either water species (H<sub>2<\/sub>O, H<sup>+<\/sup>, OH<sup>-<\/sup>) or solute species (the cations and anions of the compound). As an example, the electrolysis of aqueous sodium chloride could involve either of these two anode reactions:<\/p>\r\n\r\n<div id=\"fs-idm165376416\" style=\"padding-left: 40px\" data-type=\"equation\">(i)\u00a0 2Cl<sup>\u2212<\/sup>(<em>aq<\/em>) \u27f6 Cl<sub>2<\/sub>(<em>g<\/em>) + 2e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.35827 V<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">(ii)\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 O<sub>2<\/sub>(<em>g<\/em>) + 4H<sup>+<\/sup>(<em>aq<\/em>) + 4e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.229 V<\/div>\r\n<p id=\"fs-idm172416352\">The standard electrode (<em data-effect=\"italics\">reduction<\/em>) potentials of these two half-reactions indicate water may be <em data-effect=\"italics\">oxidized<\/em> at a less negative\/more positive potential (\u20131.229 V) than chloride ion (\u20131.358 V). Thermodynamics thus predicts that water would be more readily oxidized, though in practice it is observed that both water and chloride ion are oxidized under typical conditions, producing a mixture of oxygen and chlorine gas.<\/p>\r\n<p id=\"fs-idp30637792\">Turning attention to the cathode, the possibilities for reduction are:<\/p>\r\n\r\n<div id=\"fs-idm37951824\" style=\"padding-left: 40px\" data-type=\"equation\">(iii)\u00a0 2H<sup>+<\/sup>(<em>aq<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = 0 V<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">(iv)\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>) + 2OH<sup>\u2212<\/sup>(<em>aq<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = \u22120.8277 V<\/div>\r\n<div style=\"padding-left: 40px\" data-type=\"equation\">(v)\u00a0 Na<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup> \u27f6 Na(<em>s<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = \u22122.71 V<\/div>\r\n<p id=\"fs-idm194552416\">Comparison of these <em data-effect=\"italics\">standard<\/em> half-reaction potentials suggests the reduction of hydrogen ion is thermodynamically favored. However, in a neutral aqueous sodium chloride solution, the concentration of hydrogen ion is far below the standard state value of 1 <em data-effect=\"italics\">M<\/em> (approximately 10<sup>-7<\/sup><em data-effect=\"italics\">M<\/em>), and so the observed cathode reaction is actually reduction of water. The net cell reaction in this case is then<\/p>\r\n\r\n<div id=\"fs-idm146681264\" style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) + 2Cl<sup>\u2212<\/sup>(<em>aq<\/em>) \u27f6 H<sub>2<\/sub>(<em>g<\/em>) + Cl<sub>2<\/sub>(<em>g<\/em>) + 2OH<sup>\u2212<\/sup>(<em>aq<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cell<\/sub> = -2.186 V<\/div>\r\n<p id=\"fs-idm37680480\">This electrolysis reaction is part of the <em data-effect=\"italics\">chlor-alkali process<\/em> used by industry to produce chlorine and sodium hydroxide (lye).<\/p>\r\n&nbsp;\r\n<div id=\"fs-idm153943488\" class=\"chemistry everyday-life\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Electroplating<\/strong><\/div>\r\n<p id=\"fs-idm182126896\">An important use for electrolytic cells is in <span data-type=\"term\">electroplating<\/span>. Electroplating results in a thin coating of one metal on top of a conducting surface. Reasons for electroplating include making the object more corrosion resistant, strengthening the surface, producing a more attractive finish, or for purifying metal. The metals commonly used in electroplating include cadmium, chromium, copper, gold, nickel, silver, and tin. Common consumer products include silver-plated or gold-plated tableware, chrome-plated automobile parts, and jewelry. The silver plating of eating utensils is used here to illustrate the process. (<a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_Electroplate\">(Figure)<\/a>).<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_17_07_Electroplate\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">This schematic shows an electrolytic cell for silver plating eating utensils.<\/div>\r\n<span id=\"fs-idp6902432\" data-type=\"media\" data-alt=\"This figure contains a diagram of an electrochemical cell. One beakers is shown that is just over half full. The beaker contains a clear, colorless solution that is labeled \u201cA g N O subscript 3 ( a q ).\u201d A silver strip is mostly submerged in the liquid on the left. This strip is labeled \u201cSilver (anode).\u201d The top of the strip is labeled with a red plus symbol. An arrow points right from the surface of the metal strip into the solution to the label \u201cA g superscript plus\u201d to the right. A spoon is similarly suspended in the solution and is labeled \u201cSpoon (cathode).\u201d It is labeled with a black negative sign on the tip of the spoon\u2019s handle above the surface of the liquid. An arrow extends from the label \u201cA g superscript plus\u201d to the spoon on the right. A wire extends from the top of the spoon and the strip to a rectangle labeled \u201cVoltage source.\u201d An arrow points upward from silver strip which is labeled \u201ce superscript negative.\u201d Similarly, an arrow points down at the right to the surface of the spoon which is also labeled \u201ce superscript negative.\u201d A plus sign is shown just outside the voltage source to the left and a negative is shown to its right.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_Electroplate.jpg\" alt=\"This figure contains a diagram of an electrochemical cell. One beakers is shown that is just over half full. The beaker contains a clear, colorless solution that is labeled \u201cA g N O subscript 3 ( a q ).\u201d A silver strip is mostly submerged in the liquid on the left. This strip is labeled \u201cSilver (anode).\u201d The top of the strip is labeled with a red plus symbol. An arrow points right from the surface of the metal strip into the solution to the label \u201cA g superscript plus\u201d to the right. A spoon is similarly suspended in the solution and is labeled \u201cSpoon (cathode).\u201d It is labeled with a black negative sign on the tip of the spoon\u2019s handle above the surface of the liquid. An arrow extends from the label \u201cA g superscript plus\u201d to the spoon on the right. A wire extends from the top of the spoon and the strip to a rectangle labeled \u201cVoltage source.\u201d An arrow points upward from silver strip which is labeled \u201ce superscript negative.\u201d Similarly, an arrow points down at the right to the surface of the spoon which is also labeled \u201ce superscript negative.\u201d A plus sign is shown just outside the voltage source to the left and a negative is shown to its right.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idm52313424\">In the figure, the anode consists of a silver electrode, shown on the left. The cathode is located on the right and is the spoon, which is made from inexpensive metal. Both electrodes are immersed in a solution of silver nitrate. Applying a sufficient potential results in the oxidation of the silver anode<\/p>\r\n\r\n<div id=\"fs-idm36008608\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 Ag(<em>s<\/em>) \u27f6 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup><\/div>\r\n<p id=\"fs-idm104543584\">and reduction of silver ion at the (spoon) cathode:<\/p>\r\n\r\n<div id=\"fs-idm27151168\" style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup> \u27f6 Ag(<em>s<\/em>)<\/div>\r\n<p id=\"fs-idm28358112\">The net result is the transfer of silver metal from the anode to the cathode. Several experimental factors must be carefully controlled to obtain high-quality silver coatings, including the exact composition of the electrolyte solution, the cell voltage applied, and the rate of the electrolysis reaction (electrical current).<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm135232752\" class=\"bc-section section\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Quantitative Aspects of Electrolysis<\/strong><\/h3>\r\n<p id=\"fs-idp48850016\">Electrical current is defined as the rate of flow for any charged species. Most relevant to this discussion is the flow of electrons. Current is measured in a composite unit called an ampere, defined as one coulomb per second (A = 1 C\/s). The charge transferred, <em data-effect=\"italics\">Q<\/em>, by passage of a constant current, <em data-effect=\"italics\">I<\/em>, over a specified time interval, <em data-effect=\"italics\">t<\/em>, is then given by the simple mathematical product<\/p>\r\n\r\n<div id=\"fs-idm199736560\" style=\"padding-left: 40px\" data-type=\"equation\"><em>Q<\/em> = <em>It<\/em><\/div>\r\n<p id=\"fs-idm90272368\">When electrons are transferred during a redox process, the stoichiometry of the reaction may be used to derive the total amount of (electronic) charge involved. For example, the generic reduction process<\/p>\r\n\r\n<div id=\"fs-idm357954672\" style=\"padding-left: 40px\" data-type=\"equation\">M<sup>n+<\/sup>(<em>aq<\/em>) + <em>n<\/em>e<sup>\u2212<\/sup> \u27f6 M(<em>s<\/em>)<\/div>\r\n<p id=\"fs-idm90332432\">involves the transfer of <em data-effect=\"italics\">n<\/em> mole of electrons. The charge transferred is, therefore,<\/p>\r\n\r\n<div id=\"fs-idm389355760\" style=\"padding-left: 40px\" data-type=\"equation\"><em>Q<\/em> = <em>nF<\/em><\/div>\r\n<p id=\"fs-idm371971168\">where <em data-effect=\"italics\">F<\/em> is Faraday\u2019s constant, the charge in coulombs for one mole of electrons. If the reaction takes place in an electrochemical cell, the current flow is conveniently measured, and it may be used to assist in stoichiometric calculations related to the cell reaction.<\/p>\r\n\r\n<div id=\"fs-idm34493360\" class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"fs-idm194716208\"><strong>Converting Current to Moles of Electrons <\/strong><\/p>\r\nIn one process used for electroplating silver, a current of 10.23 A was passed through an electrolytic cell for exactly 1 hour. How many moles of electrons passed through the cell? What mass of silver was deposited at the cathode from the silver nitrate solution?\r\n<p id=\"fs-idm117750304\"><strong>Solution:<\/strong><\/p>\r\nFaraday\u2019s constant can be used to convert the charge (<em data-effect=\"italics\">Q<\/em>) into moles of electrons (<em data-effect=\"italics\">n<\/em>). The charge is the current (<em data-effect=\"italics\">I<\/em>) multiplied by the time\r\n<div id=\"fs-idm184726272\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2086\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-300x28.png\" alt=\"\" width=\"450\" height=\"42\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm196164496\">From the problem, the solution contains AgNO<sub>3<\/sub>, so the reaction at the cathode involves 1 mole of electrons for each mole of silver<\/p>\r\n\r\n<div id=\"fs-idm34803168\" style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212 <\/sup>\u27f6 Ag(<em>s<\/em>)<\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm34245792\">The atomic mass of silver is 107.9 g\/mol, so<\/p>\r\n\r\n<div id=\"fs-idm119439696\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2087\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-300x26.png\" alt=\"\" width=\"438\" height=\"38\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm156206976\"><strong>Check Your Learning:<\/strong><\/p>\r\nAluminum metal can be made from aluminum(III) ions by electrolysis. What is the half-reaction at the cathode? What mass of aluminum metal would be recovered if a current of 25.0 A passed through the solution for 15.0 minutes?\r\n\r\n&nbsp;\r\n<div id=\"fs-idm28202384\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\r\n<p id=\"fs-idp74418928\">Al<sup>3+<\/sup>(<em>aq<\/em>) + 3e<sup>\u2212<\/sup> \u27f6Al(<em>s<\/em>); 0.0777 mol Al = 2.10 g Al.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm33432704\" class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"fs-idm180222336\"><strong>Time Required for Deposition <\/strong><\/p>\r\nIn one application, a 0.010-mm layer of chromium must be deposited on a part with a total surface area of 3.3 m<sup>2<\/sup> from a solution of containing chromium(III) ions. How long would it take to deposit the layer of chromium if the current was 33.46 A? The density of chromium (metal) is 7.19 g\/cm<sup>3<\/sup>.\r\n<p id=\"fs-idp14564880\"><strong>Solution:<\/strong><\/p>\r\nFirst, compute the volume of chromium that must be produced (equal to the product of surface area and thickness):\r\n<div id=\"fs-idm83716288\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2088\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-300x24.png\" alt=\"\" width=\"438\" height=\"35\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm171372560\">Use the computed volume and the provided density to calculate the molar amount of chromium required:<\/p>\r\n\r\n<div id=\"fs-idm145248288\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2089\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-300x82.png\" alt=\"\" width=\"359\" height=\"98\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm2746496\">The stoichiometry of the chromium(III) reduction process requires three moles of electrons for each mole of chromium(0) produced, and so the total charge required is:<\/p>\r\n\r\n<div id=\"fs-idm168712592\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2091\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-300x31.png\" alt=\"\" width=\"445\" height=\"46\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm154329376\">Finally, if this charge is passed at a rate of 33.46 C\/s, the required time is:<\/p>\r\n\r\n<div id=\"fs-idm194820160\" style=\"padding-left: 40px\" data-type=\"equation\"><img class=\"alignnone wp-image-2092\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-300x36.png\" alt=\"\" width=\"333\" height=\"40\" \/><\/div>\r\n<div data-type=\"equation\"><\/div>\r\n<p id=\"fs-idm135932032\"><strong>Check Your Learning:<\/strong><\/p>\r\nWhat mass of zinc is required to galvanize the top of a 3.00 m \u00d7 5.50 m sheet of iron to a thickness of 0.100 mm of zinc? If the zinc comes from a solution of Zn(NO<sub>3<\/sub>)<sub>2<\/sub> and the current is 25.5 A, how long will it take to galvanize the top of the iron? The density of zinc is 7.140 g\/cm<sup>3<\/sup>.\r\n\r\n&nbsp;\r\n<div id=\"fs-idm206575840\" data-type=\"note\">\r\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\r\n<p id=\"fs-idm188224944\">11.8 kg Zn requires 382 hours.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp28955808\" class=\"summary\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\r\n<p id=\"fs-idm118987184\">Nonspontaneous redox processes may be forced to occur in electrochemical cells by the application of an appropriate potential using an external power source\u2014a process known as electrolysis. Electrolysis is the basis for certain ore refining processes, the industrial production of many chemical commodities, and the electroplating of metal coatings on various products. Measurement of the current flow during electrolysis permits stoichiometric calculations.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm102923952\" class=\"key-equations\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Key Equations<\/strong><\/h3>\r\n<ul id=\"fs-idm151238256\" data-bullet-style=\"bullet\">\r\n \t<li><em data-effect=\"italics\">Q<\/em> = <em data-effect=\"italics\">I<\/em> \u00d7 <em data-effect=\"italics\">t<\/em> = <em data-effect=\"italics\">n<\/em> \u00d7 <em data-effect=\"italics\">F<\/em><\/li>\r\n<\/ul>\r\n<\/div>\r\n<div id=\"fs-idm194007232\" class=\"exercises\" data-depth=\"1\">\r\n<div id=\"fs-idm13758224\" data-type=\"exercise\">\r\n<div id=\"fs-idm169556880\" data-type=\"problem\">\r\n<p id=\"fs-idm92543968\"><\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\" data-type=\"glossary\">\r\n<h3 data-type=\"glossary-title\"><strong>Glossary<\/strong><\/h3>\r\n<dl id=\"fs-idm213056464\">\r\n \t<dt>electrolysis<\/dt>\r\n \t<dd id=\"fs-idp18847920\">process using electrical energy to cause a nonspontaneous process to occur<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-idm117181824\">\r\n \t<dt>electrolytic cell<\/dt>\r\n \t<dd id=\"fs-idm168733936\">electrochemical cell in which an external source of electrical power is used to drive an otherwise nonspontaneous process<\/dd>\r\n<\/dl>\r\n<\/div>","rendered":"<p>&nbsp;<\/p>\n<div class=\"textbox textbox--learning-objectives\">\n<h3><strong>Learning Objectives<\/strong><\/h3>\n<p>By the end of this section you will be able to:<\/p>\n<ul>\n<li>Describe the process of electrolysis<\/li>\n<li>Compare the operation of electrolytic cells with that of galvanic cells<\/li>\n<li>Perform stoichiometric calculations for electrolytic processes<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idm133590080\">Electrochemical cells in which spontaneous redox reactions take place (<em data-effect=\"italics\">galvanic cells<\/em>) have been the topic of discussion so far in this chapter. In these cells, <em data-effect=\"italics\">electrical work is done by a redox system on its surroundings<\/em> as electrons produced by the redox reaction are transferred through an external circuit. This final section of the chapter will address an alternative scenario in which <em data-effect=\"italics\">an external circuit does work on a redox system<\/em> by imposing a voltage sufficient to drive an otherwise nonspontaneous reaction, a process known as <strong>electrolysis<\/strong>. A familiar example of electrolysis is recharging a battery, which involves use of an external power source to drive the spontaneous (discharge) cell reaction in the reverse direction, restoring to some extent the composition of the half-cells and the voltage of the battery. Perhaps less familiar is the use of electrolysis in the refinement of metallic ores, the manufacture of commodity chemicals, and the <em data-effect=\"italics\">electroplating<\/em> of metallic coatings on various products (e.g., jewelry, utensils, auto parts). To illustrate the essential concepts of electrolysis, a few specific processes will be considered.<\/p>\n<div id=\"fs-idp7089472\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>The Electrolysis of Molten Sodium Chloride<\/strong><\/h3>\n<p id=\"fs-idm157333328\">Metallic sodium, Na, and chlorine gas, Cl<sub>2<\/sub>, are used in numerous applications, and their industrial production relies on the large-scale electrolysis of molten sodium chloride, NaCl(<em data-effect=\"italics\">l<\/em>). The industrial process typically uses a <em data-effect=\"italics\">Downs cell<\/em> similar to the simplified illustration shown in <a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_NaCl\">(Figure)<\/a>. The reactions associated with this process are:<\/p>\n<div id=\"fs-idm155730240\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 2Cl<sup>\u2212<\/sup>(<em>l<\/em>) \u27f6 Cl<sub>2<\/sub>(<em>g<\/em>) + 2e<sup>\u2212<\/sup><\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 2 \u00d7 (Na<sup>+<\/sup>(<em>l<\/em>) + e<sup>\u2212<\/sup> \u27f6 Na(<em>l<\/em>))<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2Na<sup>+<\/sup>(<em>l<\/em>) + 2Cl<sup>\u2212<\/sup>(<em>l<\/em>) \u27f6 2Na(<em>l<\/em>) + Cl<sub>2<\/sub>(<em>g<\/em>)<\/div>\n<p id=\"fs-idm174200080\">The cell potential for the above process is negative, indicating the reaction as written (decomposition of liquid NaCl) is not spontaneous. To force this reaction, <em data-effect=\"italics\">a positive potential of magnitude greater than the negative cell potential<\/em> must be applied to the cell.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_17_07_NaCl\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Cells of this sort (a cell for the electrolysis of molten sodium chloride) are used in the <em data-effect=\"italics\">Downs process<\/em> for production of sodium and chlorine, and they typically use iron cathodes and carbon anodes.<\/div>\n<p><span id=\"fs-idm121873696\" data-type=\"media\" data-alt=\"This diagram shows a tank containing a light blue liquid, labeled \u201cMolten N a C l.\u201d A vertical dark grey divider with small, evenly distributed dark dots, labeled \u201cPorous screen\u201d is located at the center of the tank dividing it into two halves. Dark grey bars are positioned at the center of each of the halves of the tank. The bar on the left, which is labeled \u201cAnode\u201d has green bubbles originating from it. The bar on the right which is labeled \u201cCathode\u201d has light grey bubbles originating from it. An arrow points left from the center of the tank toward the anode, which is labeled \u201cC l superscript negative.\u201d An arrow points right from the center of the tank toward the cathode, which is labeled \u201cN a superscript plus.\u201d A line extends from the tops of the anode and cathode to a rectangle centrally placed above the tank which is labeled \u201cVoltage source.\u201d An arrow extends upward above the anode to the left of the line which is labeled \u201ce superscript negative.\u201d A plus symbol is located to the left of the voltage source and a negative sign it located to its right. An arrow points downward along the line segment leading to the cathode. This arrow is labeled \u201ce superscript negative.\u201d The left side of below the diagram is the label \u201c2 C l superscript negative right pointing arrow C l subscript 2 ( g ) plus 2 e superscript negative.\u201d At the right, below the diagram is the label \u201c2 N a superscript plus plus 2 e superscript negative right pointing arrow 2 N a ( l ).\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_NaCl.jpg\" alt=\"This diagram shows a tank containing a light blue liquid, labeled \u201cMolten N a C l.\u201d A vertical dark grey divider with small, evenly distributed dark dots, labeled \u201cPorous screen\u201d is located at the center of the tank dividing it into two halves. Dark grey bars are positioned at the center of each of the halves of the tank. The bar on the left, which is labeled \u201cAnode\u201d has green bubbles originating from it. The bar on the right which is labeled \u201cCathode\u201d has light grey bubbles originating from it. An arrow points left from the center of the tank toward the anode, which is labeled \u201cC l superscript negative.\u201d An arrow points right from the center of the tank toward the cathode, which is labeled \u201cN a superscript plus.\u201d A line extends from the tops of the anode and cathode to a rectangle centrally placed above the tank which is labeled \u201cVoltage source.\u201d An arrow extends upward above the anode to the left of the line which is labeled \u201ce superscript negative.\u201d A plus symbol is located to the left of the voltage source and a negative sign it located to its right. An arrow points downward along the line segment leading to the cathode. This arrow is labeled \u201ce superscript negative.\u201d The left side of below the diagram is the label \u201c2 C l superscript negative right pointing arrow C l subscript 2 ( g ) plus 2 e superscript negative.\u201d At the right, below the diagram is the label \u201c2 N a superscript plus plus 2 e superscript negative right pointing arrow 2 N a ( l ).\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm118223680\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>The Electrolysis of Water<\/strong><\/h3>\n<p id=\"fs-idm178403632\">Water may be electrolytically decomposed in a cell similar to the one illustrated in <a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_Water\">(Figure)<\/a>. To improve electrical conductivity without introducing a different redox species, the hydrogen ion concentration of the water is typically increased by addition of a strong acid. The redox processes associated with this cell are<\/p>\n<div id=\"fs-idm33413904\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 O<sub>2<\/sub>(<em>g<\/em>) + 4H<sup>+<\/sup>(<em>aq<\/em>) + 4e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.229 V<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 2 \u00d7(2H<sup>+<\/sup>(<em>aq<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>))\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = 0 V<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 2H<sub>2<\/sub>(<em>g<\/em>) + O<sub>2<\/sub>(g)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cell<\/sub> = \u22121.229 V<\/div>\n<p id=\"fs-idp152393360\">Again, the cell potential as written is negative, indicating a nonspontaneous cell reaction that must be driven by imposing a cell voltage greater than +1.229 V. Keep in mind that <em data-effect=\"italics\">standard<\/em> electrode potentials are used to inform thermodynamic predictions here, though the cell is <em data-effect=\"italics\">not<\/em> operating under standard state conditions. Therefore, at best, calculated cell potentials should be considered ballpark estimates.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_17_07_Water\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">The electrolysis of water produces stoichiometric amounts of oxygen gas at the anode and hydrogen at the anode.<\/div>\n<p><span id=\"fs-idm328048\" data-type=\"media\" data-alt=\"This figure shows an apparatus used for electrolysis. A central chamber with an open top has a vertical column extending below that is nearly full of a clear, colorless liquid, which is labeled \u201cH subscript 2 O plus H subscript 2 S O subscript 4.\u201d A horizontal tube in the apparatus connects the central region to vertical columns to the left and right, each of which has a valve or stopcock at the top and a stoppered bottom. On the left, the stopper at the bottom has a small brown square connected just above it in the liquid. The square is labeled \u201cAnode plus.\u201d A black wire extends from the stopper at the left to a rectangle which is labeled \u201cVoltage source\u201d on to the stopper at the right. The left side of the rectangle is labeled with a plus symbol and the right side is labeled with a negative sign. The stopper on the right also has a brown square connected to it which is in the liquid in the apparatus. This square is labeled \u201cCathode negative.\u201d The level of the solution on the left arm or tube of the apparatus is significantly higher than the level of the right arm. Bubbles are present near the surface of the liquid on each side of the apparatus, with the bubbles labeled as \u201cO subscript 2 ( g )\u201d on the left and \u201cH subscript 2 ( g )\u201d on the right.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_Water.jpg\" alt=\"This figure shows an apparatus used for electrolysis. A central chamber with an open top has a vertical column extending below that is nearly full of a clear, colorless liquid, which is labeled \u201cH subscript 2 O plus H subscript 2 S O subscript 4.\u201d A horizontal tube in the apparatus connects the central region to vertical columns to the left and right, each of which has a valve or stopcock at the top and a stoppered bottom. On the left, the stopper at the bottom has a small brown square connected just above it in the liquid. The square is labeled \u201cAnode plus.\u201d A black wire extends from the stopper at the left to a rectangle which is labeled \u201cVoltage source\u201d on to the stopper at the right. The left side of the rectangle is labeled with a plus symbol and the right side is labeled with a negative sign. The stopper on the right also has a brown square connected to it which is in the liquid in the apparatus. This square is labeled \u201cCathode negative.\u201d The level of the solution on the left arm or tube of the apparatus is significantly higher than the level of the right arm. Bubbles are present near the surface of the liquid on each side of the apparatus, with the bubbles labeled as \u201cO subscript 2 ( g )\u201d on the left and \u201cH subscript 2 ( g )\u201d on the right.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm95712768\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>The Electrolysis of Aqueous Sodium Chloride<\/strong><\/h3>\n<p id=\"fs-idm37835104\">When aqueous solutions of ionic compounds are electrolyzed, the anode and cathode half-reactions may involve the electrolysis of either water species (H<sub>2<\/sub>O, H<sup>+<\/sup>, OH<sup>&#8211;<\/sup>) or solute species (the cations and anions of the compound). As an example, the electrolysis of aqueous sodium chloride could involve either of these two anode reactions:<\/p>\n<div id=\"fs-idm165376416\" style=\"padding-left: 40px\" data-type=\"equation\">(i)\u00a0 2Cl<sup>\u2212<\/sup>(<em>aq<\/em>) \u27f6 Cl<sub>2<\/sub>(<em>g<\/em>) + 2e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.35827 V<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">(ii)\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) \u27f6 O<sub>2<\/sub>(<em>g<\/em>) + 4H<sup>+<\/sup>(<em>aq<\/em>) + 4e<sup>\u2212<\/sup>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>anode<\/sub> = +1.229 V<\/div>\n<p id=\"fs-idm172416352\">The standard electrode (<em data-effect=\"italics\">reduction<\/em>) potentials of these two half-reactions indicate water may be <em data-effect=\"italics\">oxidized<\/em> at a less negative\/more positive potential (\u20131.229 V) than chloride ion (\u20131.358 V). Thermodynamics thus predicts that water would be more readily oxidized, though in practice it is observed that both water and chloride ion are oxidized under typical conditions, producing a mixture of oxygen and chlorine gas.<\/p>\n<p id=\"fs-idp30637792\">Turning attention to the cathode, the possibilities for reduction are:<\/p>\n<div id=\"fs-idm37951824\" style=\"padding-left: 40px\" data-type=\"equation\">(iii)\u00a0 2H<sup>+<\/sup>(<em>aq<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = 0 V<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">(iv)\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) + 2e<sup>\u2212<\/sup> \u27f6 H<sub>2<\/sub>(<em>g<\/em>) + 2OH<sup>\u2212<\/sup>(<em>aq<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = \u22120.8277 V<\/div>\n<div style=\"padding-left: 40px\" data-type=\"equation\">(v)\u00a0 Na<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup> \u27f6 Na(<em>s<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cathode<\/sub> = \u22122.71 V<\/div>\n<p id=\"fs-idm194552416\">Comparison of these <em data-effect=\"italics\">standard<\/em> half-reaction potentials suggests the reduction of hydrogen ion is thermodynamically favored. However, in a neutral aqueous sodium chloride solution, the concentration of hydrogen ion is far below the standard state value of 1 <em data-effect=\"italics\">M<\/em> (approximately 10<sup>-7<\/sup><em data-effect=\"italics\">M<\/em>), and so the observed cathode reaction is actually reduction of water. The net cell reaction in this case is then<\/p>\n<div id=\"fs-idm146681264\" style=\"padding-left: 40px\" data-type=\"equation\">cell:\u00a0 2H<sub>2<\/sub>O(<em>l<\/em>) + 2Cl<sup>\u2212<\/sup>(<em>aq<\/em>) \u27f6 H<sub>2<\/sub>(<em>g<\/em>) + Cl<sub>2<\/sub>(<em>g<\/em>) + 2OH<sup>\u2212<\/sup>(<em>aq<\/em>)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 E\u00b0<sub>cell<\/sub> = -2.186 V<\/div>\n<p id=\"fs-idm37680480\">This electrolysis reaction is part of the <em data-effect=\"italics\">chlor-alkali process<\/em> used by industry to produce chlorine and sodium hydroxide (lye).<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm153943488\" class=\"chemistry everyday-life\" data-type=\"note\">\n<div data-type=\"title\"><strong>Electroplating<\/strong><\/div>\n<p id=\"fs-idm182126896\">An important use for electrolytic cells is in <span data-type=\"term\">electroplating<\/span>. Electroplating results in a thin coating of one metal on top of a conducting surface. Reasons for electroplating include making the object more corrosion resistant, strengthening the surface, producing a more attractive finish, or for purifying metal. The metals commonly used in electroplating include cadmium, chromium, copper, gold, nickel, silver, and tin. Common consumer products include silver-plated or gold-plated tableware, chrome-plated automobile parts, and jewelry. The silver plating of eating utensils is used here to illustrate the process. (<a class=\"autogenerated-content\" href=\"#CNX_Chem_17_07_Electroplate\">(Figure)<\/a>).<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_17_07_Electroplate\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">This schematic shows an electrolytic cell for silver plating eating utensils.<\/div>\n<p><span id=\"fs-idp6902432\" data-type=\"media\" data-alt=\"This figure contains a diagram of an electrochemical cell. One beakers is shown that is just over half full. The beaker contains a clear, colorless solution that is labeled \u201cA g N O subscript 3 ( a q ).\u201d A silver strip is mostly submerged in the liquid on the left. This strip is labeled \u201cSilver (anode).\u201d The top of the strip is labeled with a red plus symbol. An arrow points right from the surface of the metal strip into the solution to the label \u201cA g superscript plus\u201d to the right. A spoon is similarly suspended in the solution and is labeled \u201cSpoon (cathode).\u201d It is labeled with a black negative sign on the tip of the spoon\u2019s handle above the surface of the liquid. An arrow extends from the label \u201cA g superscript plus\u201d to the spoon on the right. A wire extends from the top of the spoon and the strip to a rectangle labeled \u201cVoltage source.\u201d An arrow points upward from silver strip which is labeled \u201ce superscript negative.\u201d Similarly, an arrow points down at the right to the surface of the spoon which is also labeled \u201ce superscript negative.\u201d A plus sign is shown just outside the voltage source to the left and a negative is shown to its right.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_17_07_Electroplate.jpg\" alt=\"This figure contains a diagram of an electrochemical cell. One beakers is shown that is just over half full. The beaker contains a clear, colorless solution that is labeled \u201cA g N O subscript 3 ( a q ).\u201d A silver strip is mostly submerged in the liquid on the left. This strip is labeled \u201cSilver (anode).\u201d The top of the strip is labeled with a red plus symbol. An arrow points right from the surface of the metal strip into the solution to the label \u201cA g superscript plus\u201d to the right. A spoon is similarly suspended in the solution and is labeled \u201cSpoon (cathode).\u201d It is labeled with a black negative sign on the tip of the spoon\u2019s handle above the surface of the liquid. An arrow extends from the label \u201cA g superscript plus\u201d to the spoon on the right. A wire extends from the top of the spoon and the strip to a rectangle labeled \u201cVoltage source.\u201d An arrow points upward from silver strip which is labeled \u201ce superscript negative.\u201d Similarly, an arrow points down at the right to the surface of the spoon which is also labeled \u201ce superscript negative.\u201d A plus sign is shown just outside the voltage source to the left and a negative is shown to its right.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idm52313424\">In the figure, the anode consists of a silver electrode, shown on the left. The cathode is located on the right and is the spoon, which is made from inexpensive metal. Both electrodes are immersed in a solution of silver nitrate. Applying a sufficient potential results in the oxidation of the silver anode<\/p>\n<div id=\"fs-idm36008608\" style=\"padding-left: 40px\" data-type=\"equation\">anode:\u00a0 Ag(<em>s<\/em>) \u27f6 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup><\/div>\n<p id=\"fs-idm104543584\">and reduction of silver ion at the (spoon) cathode:<\/p>\n<div id=\"fs-idm27151168\" style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212<\/sup> \u27f6 Ag(<em>s<\/em>)<\/div>\n<p id=\"fs-idm28358112\">The net result is the transfer of silver metal from the anode to the cathode. Several experimental factors must be carefully controlled to obtain high-quality silver coatings, including the exact composition of the electrolyte solution, the cell voltage applied, and the rate of the electrolysis reaction (electrical current).<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm135232752\" class=\"bc-section section\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Quantitative Aspects of Electrolysis<\/strong><\/h3>\n<p id=\"fs-idp48850016\">Electrical current is defined as the rate of flow for any charged species. Most relevant to this discussion is the flow of electrons. Current is measured in a composite unit called an ampere, defined as one coulomb per second (A = 1 C\/s). The charge transferred, <em data-effect=\"italics\">Q<\/em>, by passage of a constant current, <em data-effect=\"italics\">I<\/em>, over a specified time interval, <em data-effect=\"italics\">t<\/em>, is then given by the simple mathematical product<\/p>\n<div id=\"fs-idm199736560\" style=\"padding-left: 40px\" data-type=\"equation\"><em>Q<\/em> = <em>It<\/em><\/div>\n<p id=\"fs-idm90272368\">When electrons are transferred during a redox process, the stoichiometry of the reaction may be used to derive the total amount of (electronic) charge involved. For example, the generic reduction process<\/p>\n<div id=\"fs-idm357954672\" style=\"padding-left: 40px\" data-type=\"equation\">M<sup>n+<\/sup>(<em>aq<\/em>) + <em>n<\/em>e<sup>\u2212<\/sup> \u27f6 M(<em>s<\/em>)<\/div>\n<p id=\"fs-idm90332432\">involves the transfer of <em data-effect=\"italics\">n<\/em> mole of electrons. The charge transferred is, therefore,<\/p>\n<div id=\"fs-idm389355760\" style=\"padding-left: 40px\" data-type=\"equation\"><em>Q<\/em> = <em>nF<\/em><\/div>\n<p id=\"fs-idm371971168\">where <em data-effect=\"italics\">F<\/em> is Faraday\u2019s constant, the charge in coulombs for one mole of electrons. If the reaction takes place in an electrochemical cell, the current flow is conveniently measured, and it may be used to assist in stoichiometric calculations related to the cell reaction.<\/p>\n<div id=\"fs-idm34493360\" class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"fs-idm194716208\"><strong>Converting Current to Moles of Electrons <\/strong><\/p>\n<p>In one process used for electroplating silver, a current of 10.23 A was passed through an electrolytic cell for exactly 1 hour. How many moles of electrons passed through the cell? What mass of silver was deposited at the cathode from the silver nitrate solution?<\/p>\n<p id=\"fs-idm117750304\"><strong>Solution:<\/strong><\/p>\n<p>Faraday\u2019s constant can be used to convert the charge (<em data-effect=\"italics\">Q<\/em>) into moles of electrons (<em data-effect=\"italics\">n<\/em>). The charge is the current (<em data-effect=\"italics\">I<\/em>) multiplied by the time<\/p>\n<div id=\"fs-idm184726272\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2086\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-300x28.png\" alt=\"\" width=\"450\" height=\"42\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-300x28.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-1024x96.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-768x72.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-1536x145.png 1536w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-65x6.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-225x21.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a-350x33.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7a.png 1731w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm196164496\">From the problem, the solution contains AgNO<sub>3<\/sub>, so the reaction at the cathode involves 1 mole of electrons for each mole of silver<\/p>\n<div id=\"fs-idm34803168\" style=\"padding-left: 40px\" data-type=\"equation\">cathode:\u00a0 Ag<sup>+<\/sup>(<em>aq<\/em>) + e<sup>\u2212 <\/sup>\u27f6 Ag(<em>s<\/em>)<\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm34245792\">The atomic mass of silver is 107.9 g\/mol, so<\/p>\n<div id=\"fs-idm119439696\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2087\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-300x26.png\" alt=\"\" width=\"438\" height=\"38\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-300x26.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-1024x88.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-768x66.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-65x6.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-225x19.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b-350x30.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7b.png 1438w\" sizes=\"auto, (max-width: 438px) 100vw, 438px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm156206976\"><strong>Check Your Learning:<\/strong><\/p>\n<p>Aluminum metal can be made from aluminum(III) ions by electrolysis. What is the half-reaction at the cathode? What mass of aluminum metal would be recovered if a current of 25.0 A passed through the solution for 15.0 minutes?<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm28202384\" data-type=\"note\">\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\n<p id=\"fs-idp74418928\">Al<sup>3+<\/sup>(<em>aq<\/em>) + 3e<sup>\u2212<\/sup> \u27f6Al(<em>s<\/em>); 0.0777 mol Al = 2.10 g Al.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm33432704\" class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"fs-idm180222336\"><strong>Time Required for Deposition <\/strong><\/p>\n<p>In one application, a 0.010-mm layer of chromium must be deposited on a part with a total surface area of 3.3 m<sup>2<\/sup> from a solution of containing chromium(III) ions. How long would it take to deposit the layer of chromium if the current was 33.46 A? The density of chromium (metal) is 7.19 g\/cm<sup>3<\/sup>.<\/p>\n<p id=\"fs-idp14564880\"><strong>Solution:<\/strong><\/p>\n<p>First, compute the volume of chromium that must be produced (equal to the product of surface area and thickness):<\/p>\n<div id=\"fs-idm83716288\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2088\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-300x24.png\" alt=\"\" width=\"438\" height=\"35\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-300x24.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-1024x83.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-768x63.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-1536x125.png 1536w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-65x5.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-225x18.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c-350x28.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7c.png 1683w\" sizes=\"auto, (max-width: 438px) 100vw, 438px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm171372560\">Use the computed volume and the provided density to calculate the molar amount of chromium required:<\/p>\n<div id=\"fs-idm145248288\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2089\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-300x82.png\" alt=\"\" width=\"359\" height=\"98\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-300x82.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-1024x281.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-768x211.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-65x18.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-225x62.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d-350x96.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7d.png 1272w\" sizes=\"auto, (max-width: 359px) 100vw, 359px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm2746496\">The stoichiometry of the chromium(III) reduction process requires three moles of electrons for each mole of chromium(0) produced, and so the total charge required is:<\/p>\n<div id=\"fs-idm168712592\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2091\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-300x31.png\" alt=\"\" width=\"445\" height=\"46\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-300x31.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-1024x106.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-768x80.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-65x7.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-225x23.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1-350x36.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7e-1.png 1302w\" sizes=\"auto, (max-width: 445px) 100vw, 445px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm154329376\">Finally, if this charge is passed at a rate of 33.46 C\/s, the required time is:<\/p>\n<div id=\"fs-idm194820160\" style=\"padding-left: 40px\" data-type=\"equation\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-2092\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-300x36.png\" alt=\"\" width=\"333\" height=\"40\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-300x36.png 300w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-1024x125.png 1024w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-768x93.png 768w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-65x8.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-225x27.png 225w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f-350x43.png 350w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/17.7f.png 1044w\" sizes=\"auto, (max-width: 333px) 100vw, 333px\" \/><\/div>\n<div data-type=\"equation\"><\/div>\n<p id=\"fs-idm135932032\"><strong>Check Your Learning:<\/strong><\/p>\n<p>What mass of zinc is required to galvanize the top of a 3.00 m \u00d7 5.50 m sheet of iron to a thickness of 0.100 mm of zinc? If the zinc comes from a solution of Zn(NO<sub>3<\/sub>)<sub>2<\/sub> and the current is 25.5 A, how long will it take to galvanize the top of the iron? The density of zinc is 7.140 g\/cm<sup>3<\/sup>.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"fs-idm206575840\" data-type=\"note\">\n<div data-type=\"title\"><strong>Answer:<\/strong><\/div>\n<p id=\"fs-idm188224944\">11.8 kg Zn requires 382 hours.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idp28955808\" class=\"summary\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\n<p id=\"fs-idm118987184\">Nonspontaneous redox processes may be forced to occur in electrochemical cells by the application of an appropriate potential using an external power source\u2014a process known as electrolysis. Electrolysis is the basis for certain ore refining processes, the industrial production of many chemical commodities, and the electroplating of metal coatings on various products. Measurement of the current flow during electrolysis permits stoichiometric calculations.<\/p>\n<\/div>\n<div id=\"fs-idm102923952\" class=\"key-equations\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Key Equations<\/strong><\/h3>\n<ul id=\"fs-idm151238256\" data-bullet-style=\"bullet\">\n<li><em data-effect=\"italics\">Q<\/em> = <em data-effect=\"italics\">I<\/em> \u00d7 <em data-effect=\"italics\">t<\/em> = <em data-effect=\"italics\">n<\/em> \u00d7 <em data-effect=\"italics\">F<\/em><\/li>\n<\/ul>\n<\/div>\n<div id=\"fs-idm194007232\" class=\"exercises\" data-depth=\"1\">\n<div id=\"fs-idm13758224\" data-type=\"exercise\">\n<div id=\"fs-idm169556880\" data-type=\"problem\">\n<p id=\"fs-idm92543968\">\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\" data-type=\"glossary\">\n<h3 data-type=\"glossary-title\"><strong>Glossary<\/strong><\/h3>\n<dl id=\"fs-idm213056464\">\n<dt>electrolysis<\/dt>\n<dd id=\"fs-idp18847920\">process using electrical energy to cause a nonspontaneous process to occur<\/dd>\n<\/dl>\n<dl id=\"fs-idm117181824\">\n<dt>electrolytic cell<\/dt>\n<dd id=\"fs-idm168733936\">electrochemical cell in which an external source of electrical power is used to drive an otherwise nonspontaneous process<\/dd>\n<\/dl>\n<\/div>\n","protected":false},"author":1392,"menu_order":8,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-898","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":870,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/898","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/users\/1392"}],"version-history":[{"count":5,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/898\/revisions"}],"predecessor-version":[{"id":2190,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/898\/revisions\/2190"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/parts\/870"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/898\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/media?parent=898"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapter-type?post=898"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/contributor?post=898"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/license?post=898"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}