Solving a Voitaic Cell: 0.45V Electrochemical Potential

[ahhppull]

Homework Statement

A voitaic cell consists of a Zn/Zn^2+ half-cell and Ni/Ni^2+ half-cell at 25C. The initial concentration of Ni^2+ and Zn^2+ are 1.50M and .100M respectively.

What are the concentrations of Ni2+ and Zn2+ when the cell potential falls to 0.45V?

Homework Equations

Ecell = Ecell(standard) - (0.0592V/n)logK

The Attempt at a Solution

I got the correct answer, but I'm not clear on the method used to solve this problem.

When I used the Nernst equation, I got a ratio of 504 = ([Zn2+]/[Ni2+])

Why would I divide 1.50M Ni2+ by 504 to get the concentration of Zn2+ at 45V?

 

[Borek]

I don't see why dividing the way you described it makes sense. Could be I am missing something, and your description is incomplete, no idea what is what of what.

Concentrations when potential falls to 0.45V can be calculated from initial concentrations and from the reaction stoichiometry. Assume n moles of Zn²⁺ reacted and write Nernst equation for the system after reaction.