A student electroplates copper from 0.50 M CuSO4 onto a clean copper cathode. A constant current of 0.500 A is passed for 30.0 min. The cathode is dried and reweighed; the mass increases by 0.296 g. F = 96,485 C/mol e-. M(Cu) = 63.55 g/mol.
How does the experimental mass of Cu deposited compare to the theoretical mass?
- A
Theoretical = 0.296 g; experimental should be 1/2 because Cu^2+
- B
Theoretical = 0.148 g; efficiency ~200%
- Ccheck_circle
Theoretical = 0.296 g; experimental matches within rounding (~100% efficiency)
- D
Theoretical = 0.592 g; efficiency ~50%
Explanation
Q = It = 0.500*1800 = 900 C. mol e- = 900/96485 = 9.328e-3. mol Cu = 9.328e-3/2 = 4.664e-3. mass = 4.664e-3 * 63.55 = 0.296 g.