Purification of nickel can be achieved by electrorefining nickel from an impure nickel anode onto a pure nickel cathode in an electrolytic cell.

Question

How many hours will it take to plate 15.0 kg of nickel onto the cathode if the current passed through the cell is held constant at 31.5 A ? Assume the nickel in the electrolytic solution is present as Ni2+ .

Answer 1

Things to know:

1 amp = 1 coulomb/sec

96,485 coulombs (C) = charge for 1 mol electrons

1 mole Ni²⁺ requires 2 mol electrons to become Ni

Calculations:

15.0 kg x 1000 g /kg = 15000 g x 1 mol Ni / 58.7 g = 256 mols Ni

256 mols Ni x 2 mols electrons / mol Ni = 512 mols electrons

512 mols electrons x 96485 C / mol electrons = 49,400,320 C needed

49,400,320 C x 1 sec / 31.5 C = 1,568,264 sec

1,568,264 sec x 1 min / 60 sec x 1 hour / 60 min = 436 hours