electrolysis?

Question

Use the following cell to answer the questions:
Cr / Cr3+ (1.00 M) // Ni2+ (1.00 M) / Ni.
a) How many milligrams of Ni would be plated on the cathode if a current of 0.23 A is drawn for 2.8 hrs?
(answer must be in mg of Ni)

b) What is [Cr3+] when [Ni2+] has dropped to 10-4 M?
(answer must be in M)

c) What is the cell potential at the conditions described in Part b?
(answer must be in V)

Answer 1

Principles: (a) is actually just a unit conversion problem. Use

current (amp) x time (s) = amount of electric charge (C)

Charge (C)/96,486 = Faradays (1 Faraday = 1 mole electrons)

1 mole Ni corresponds to 2 moles electrons.

(b): see how many moles Ni2+ had been removed. How many moles Cr have gone into solution as Cr3+ (care! Charges must balance)

(c): you now have a cell under nonstandard conditions, and will need to use the Nernst Equation for each half reaction.