14.27

$\Delta G^{\circ} = -nFE_{cell}^{\circ}$

Liam Giffin 2B
Posts: 34
Joined: Fri Jul 22, 2016 3:00 am
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14.27

For question 14.27 in the textbook I don't understand why we can't just add the potentials of reactions A and B (shown in solution manual answer) together. The problem and solution manual solution are shown below.
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Manpreet Singh 1N
Posts: 41
Joined: Wed Sep 21, 2016 2:59 pm
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Re: 14.27

Hello,

For this problem, we want the standard potential for U^4+ +4e- ----> U

since we don't have that exact standard potential, we can use the information we have so we have:
U^4+ +e- ----> U^3+ E^o=-0.61
U^3+ +3e- -----> U E^o=-1.78 When we add, the U^3+ cancels out because they are on opposite sided of the reaction.

We know the formula is for E is E=-nE^oF so we add them and make the equal to the one we want. There are 4 moles in the one we want, there is 1 mol is the first half reaction and 3 in the second and since F is a constantsI am gonna leave it like it for simplicity sake.

-4E*F=(-1(-0.61)*F)+(-3(-1.78)*F) and you solve for E

We cant just add the values because there are different values of moles, and this way it is more precise.

hope that helps :)