{"id":3907,"date":"2026-03-27T14:36:11","date_gmt":"2026-03-27T18:36:11","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/?post_type=chapter&p=3907"},"modified":"2026-05-01T09:38:38","modified_gmt":"2026-05-01T13:38:38","slug":"quiz-solutions-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/chapter\/quiz-solutions-3\/","title":{"raw":"Quiz Solutions","rendered":"Quiz Solutions"},"content":{"raw":"1. Electrowinning is a common way to produce pure metals. However, chemical reduction is also feasible in some instances. Consider the Eh-pH diagram below. Over what pH range would you expect to be able to reduce Co +2 to cobalt metal. Explain your answer by considering the sign of \u0394E for the reaction over that pH range.\r\n\r\nFrom the diagram below the pH range for reduction of Co+2 by H2 at 10 atm pressure is about 4.56 < pH < 6.46. Above pH 4.56 EhCo+2\/Co<\/sub> > EhH+\/H2<\/sub>. The reaction is:\r\n\r\nCo+2 + H2 = Co + 2H+\r\n\r\n\u0394E = EhCo+2\/Co - EhH+\/H2 > 0 above pH 4.56.\r\n
\r\n
\r\n\r\n2. After copper solvent extraction electrowinning will be practiced to produce high-purity copper metal.\r\n\r\n(a) If the annual copper production is 45,000 tonnes per year, the PLS copper concentration is 1.9 g\/L and the extent of extraction from the PLS is 91%, what will the PLS flow rate be in m3\/h?<\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n
\r\n\r\n(i) PLS flow rate\r\n\r\nAnnual copper production:\r\n\r\n45,000 t\/y * 1000kg\/t * y\/365 days * day\/24 hrs = 5,137 kg Cu\/h\r\n\r\nCopper removed per m\u00b3:\r\n\r\n(0.91) * (1.9) = 1.71 kg\/m\u00b3\r\n\r\nPLS flow rate:\r\n\r\nA \u2248 3004 m\u00b3\/h\r\n\r\n(b) If the rich electrolyte copper concentration is 42 g\/L and the electrolyte flow rate is 570 m3\/h what will the lean electrolyte copper concentration be? (Assume 365 day\/year operation.)<\/span>\r\n\r\n(ii) Lean electrolyte concentration\r\n\r\nCopper balance:\r\n\r\nA*(CRE<\/sub> \u2212 CLE<\/sub>) = MCu<\/sub>\r\n\r\nLean electrolyte:\r\n\r\nCLE<\/sub> \u2248 33.0 g\/L\r\n\r\n3. The EW plant has four banks of 28 cells each. The current efficiency is 90%. The cathodes are 1.2 m deep x 1 m wide. The current density is about 300 A\/m2. The cell voltage is 2.05 V.<\/span>\r\n
\r\n
\r\n\r\n(a) Determine the number of cathode sheets per cell (must be an integer; round off as needed).\r\n<\/colgroup>\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Cells\/bank<\/td>\r\n<\/td>\r\n<\/td>\r\n28<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\r\n
\r\n
Cells in the plant<\/div>\r\n<\/div><\/td>\r\n
<\/td>\r\n<\/td>\r\n112<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\r\n
\r\n
Cathode sheet dimensions<\/div>\r\n<\/div><\/td>\r\n
<\/td>\r\n<\/td>\r\n\r\n
\r\n
1 m X 1.2 m<\/div>\r\n<\/div><\/td>\r\n
<\/td>\r\n<\/tr>\r\n
\r\n
\r\n
Current efficiency<\/div>\r\n<\/div><\/td>\r\n
<\/td>\r\n<\/td>\r\n90<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\r\n
\r\n
Current density (approx.)<\/div>\r\n<\/div><\/td>\r\n
<\/td>\r\n<\/td>\r\n300<\/td>\r\nA\/m2<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nN = 45000 * 100 * 2 * 96485 \/ (300*2.4*90*63.546*0.000001*3600*24*365*112) = 59.71 = 60<\/span> sheets per cell.\r\n\r\n(b) Calculate an accurate value for the current density given that the number of cathode sheets\/cell is an integer.\r\n\r\nJ = 45000*200*96485\/(2.4*60*112*90*63.546*0.000001*3600*24*365) = 298.53 <\/span>A\/m2\r\n\r\n(c)\r\n\r\n-we<\/sub>' =200*96485*2.05*1000\/(90*63.546*3600000) = 1.921<\/span> kWh\/kg Cu<\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"

1. Electrowinning is a common way to produce pure metals. However, chemical reduction is also feasible in some instances. Consider the Eh-pH diagram below. Over what pH range would you expect to be able to reduce Co +2 to cobalt metal. Explain your answer by considering the sign of \u0394E for the reaction over that pH range.<\/p>\n

From the diagram below the pH range for reduction of Co+2 by H2 at 10 atm pressure is about 4.56 < pH < 6.46. Above pH 4.56 EhCo+2\/Co<\/sub> > EhH+\/H2<\/sub>. The reaction is:<\/p>\n

Co+2 + H2 = Co + 2H+<\/p>\n

\u0394E = EhCo+2\/Co – EhH+\/H2 > 0 above pH 4.56.<\/p>\n

\n
\n

2. After copper solvent extraction electrowinning will be practiced to produce high-purity copper metal.<\/p>\n

(a) If the annual copper production is 45,000 tonnes per year, the PLS copper concentration is 1.9 g\/L and the extent of extraction from the PLS is 91%, what will the PLS flow rate be in m3\/h?<\/span><\/p>\n<\/div>\n<\/div>\n

\n
\n

(i) PLS flow rate<\/p>\n

Annual copper production:<\/p>\n

45,000 t\/y * 1000kg\/t * y\/365 days * day\/24 hrs = 5,137 kg Cu\/h<\/p>\n

Copper removed per m\u00b3:<\/p>\n

(0.91) * (1.9) = 1.71 kg\/m\u00b3<\/p>\n

PLS flow rate:<\/p>\n

A \u2248 3004 m\u00b3\/h<\/p>\n

(b) If the rich electrolyte copper concentration is 42 g\/L and the electrolyte flow rate is 570 m3\/h what will the lean electrolyte copper concentration be? (Assume 365 day\/year operation.)<\/span><\/p>\n

(ii) Lean electrolyte concentration<\/p>\n

Copper balance:<\/p>\n

A*(CRE<\/sub> \u2212 CLE<\/sub>) = MCu<\/sub><\/p>\n

Lean electrolyte:<\/p>\n

CLE<\/sub> \u2248 33.0 g\/L<\/p>\n

3. The EW plant has four banks of 28 cells each. The current efficiency is 90%. The cathodes are 1.2 m deep x 1 m wide. The current density is about 300 A\/m2. The cell voltage is 2.05 V.<\/span><\/p>\n

\n
\n

(a) Determine the number of cathode sheets per cell (must be an integer; round off as needed).<\/p>\n\n\n\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n
Cells\/bank<\/td>\n<\/td>\n<\/td>\n28<\/td>\n<\/td>\n<\/tr>\n
\n
\n
Cells in the plant<\/div>\n<\/div>\n<\/td>\n
<\/td>\n<\/td>\n112<\/td>\n<\/td>\n<\/tr>\n
\n
\n
Cathode sheet dimensions<\/div>\n<\/div>\n<\/td>\n
<\/td>\n<\/td>\n\n
\n
1 m X 1.2 m<\/div>\n<\/div>\n<\/td>\n
<\/td>\n<\/tr>\n
\n
\n
Current efficiency<\/div>\n<\/div>\n<\/td>\n
<\/td>\n<\/td>\n90<\/td>\n<\/td>\n<\/tr>\n
\n
\n
Current density (approx.)<\/div>\n<\/div>\n<\/td>\n
<\/td>\n<\/td>\n300<\/td>\nA\/m2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

N = 45000 * 100 * 2 * 96485 \/ (300*2.4*90*63.546*0.000001*3600*24*365*112) = 59.71 = 60<\/span> sheets per cell.<\/p>\n

(b) Calculate an accurate value for the current density given that the number of cathode sheets\/cell is an integer.<\/p>\n

J = 45000*200*96485\/(2.4*60*112*90*63.546*0.000001*3600*24*365) = 298.53 <\/span>A\/m2<\/p>\n

(c)<\/p>\n

-we<\/sub>‘ =200*96485*2.05*1000\/(90*63.546*3600000) = 1.921<\/span> kWh\/kg Cu<\/span><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":2529,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-3907","chapter","type-chapter","status-publish","hentry"],"part":2590,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapters\/3907","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/wp\/v2\/users\/2529"}],"version-history":[{"count":3,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapters\/3907\/revisions"}],"predecessor-version":[{"id":3945,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapters\/3907\/revisions\/3945"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/parts\/2590"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapters\/3907\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/wp\/v2\/media?parent=3907"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/pressbooks\/v2\/chapter-type?post=3907"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/wp\/v2\/contributor?post=3907"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/hydrometallurgy\/wp-json\/wp\/v2\/license?post=3907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}