Hi (sorry if my english isn't good)
I have a task with which goes like this:
A battery is based on oxidation of Magnesium and reduction of Copper-ions. The starting consentration of Mg2+-ions and Cu2+-ions are 1,0 * 10-4 M and 1,5 M. The volume of each halfcell is 1 liter.
a ) Calculate the battery-voltage at the start.
b) Calculate the battery-voltage after the battery has delivered 5,0 A for 8,0 hours.
I think i got a) right. I just calculated the cellpotential and put it in Nernst forumla like this:
Oxidation: Mg2+ + 2e- --> Mg(s) : -2.36V
Reduction: 2Cu2+ + 2e- --> 2Cu : 0.16 V
Cell potential: E = 0.16 - (-2.36) = 2,52 V
Ecell = 2,52 V - (0,0592 V / 2 ) * log([1,5 M] / 2*[1,0 * 10-4 M]) = 2,4053 V = 2,4 V
My problem is b). I tried different ways to solve it but i can't figure it out. I suspect i have to use Faraday's forumal: np = (I * t) / (F * n), but i can't figure out how to use it to find the battery-potensial.
Can anyone help me?
Sorry for but terrible translation xD
