Mass of copper plated by electrolysis
A current of 2.0 A runs for 965 s through a Cu²⁺ solution. What mass of copper is deposited? (F = 96,500 C/mol; Cu = 63.5 g/mol)
Answer B: explanation for every choice
A
This divides by 2 twice.
B
Correct. Charge = 2.0 × 965 = 1,930 C = 0.020 mol e⁻. Each Cu²⁺ needs 2 e⁻, so 0.010 mol Cu × 63.5 = 0.64 g.
C
This forgets that each Cu²⁺ needs two electrons.
D
This is off by a factor of 10, as if F were 9,650 C/mol.
Takeawaymol e⁻ = It/F, then divide by the ion's charge.
Equation usedElectrolysis (Faraday's law)
Next question →Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp169.