We’re being asked to calculate for the time it would take to selectively plate out one of the cations in the given solution.
The solution is made up of 0.110 M NiCl2(aq) and 0.200 M CuBr2(aq) and subjected to electrolysis. Both will break up in the solution:
NiCl2(aq) → Ni2+(aq) + 2 Cl-(aq)
CuBr2(aq) → Cu2+(aq)+ 2 Br-(aq)
Let’s first determine which cation (positively charged ion) will be plated out from the solution first. The one with the higher reduction potential will be plated out first.
*the standard reduction potential table (E°cell values) can be found in books or on the internet