redox. Cr2O7^2- + H2O. If oxidation of H2O occurs at the anode

redox. Cr2O7^2- + H2O. If oxidation of H2O occurs at the anode

 

 

An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr2O7^2- solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs.

If oxidation of H2O occurs at the anode, how many moles of oxygen gas will evolve for every 151 grams of Cr(s) deposited?

 

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▶ 산화 반쪽: 6H2O → 3O2 + 12H^+ + 12e^-

▶ 환원 반쪽: Cr2O7^2- + 14H^+ + 12e^- → 2Cr + 7H2O

 

▶ 전체 산화-환원 반응식

Cr2O7^2-(aq) + 2H^+(aq) → 2Cr(s) + 3O2(g) + H2O(l)

( 설명 http://ywpop.tistory.com/8398 )

 

 

151 g / (51.996 g/mol) = 2.90407 mol Cr

Cr : O2 = 2 : 3 = 2.90407 mol : ? mol

? = 3 * 2.90407 / 2 = 4.3561 mol O2

 

 

답: 4.36 mol