Copper metal is purified by electrolysis. How much copper metal could be produced from copper(II) oxide by applying a current of 10.0 amps at the appropriate negative potential for 12.0 hours?

Question

Quizplus · Accepted Answer

The amount of copper metal produced can be calculated using Faraday's constant (F) and the equation:
moles of electrons transferred = current (in amperes) × time (in seconds) ÷ Faraday's constant
Using the molar mass of CuO and stoichiometry, we can convert moles of electrons to moles of CuO, and then to mass of Cu:
CuO + H2O → Cu + O2 + H2O
1 mol e^- (or 1 F) transfers 2 mol of Cu:
2 mol Cu / 1 mol e^-
The appropriate negative potential for the reduction of CuO is -0.34 V (from a table of standard reduction potentials).
F = 96485 C/mol e^- (or 96485 A·s/mol e^-)
10.0 A × (12.0 h × 3600 s/h) = 4.32 × 10^5 C
moles of electrons transferred = 4.32 × 10^5 C ÷ 96485 C/mol e^- = 4.48 mol e^-
moles of Cu produced = 0.5 × 4.48 mol e^- = 2.24 mol Cu
mass of Cu produced = 2.24 mol × 63.55 g/mol = 142 g

Copper Metal Is Purified by Electrolysis