## Test 2

Nora 1F
Posts: 46
Joined: Fri Sep 29, 2017 7:04 am

### Test 2

While reviewing my tests I was unsure about why one of the problems was marked incorrect. The question asked to calculate the standard potential for the following reaction using given reduction potentials.

Fe^3+ (aq) + 3e- --> Fe (s)

Fe^3+ (aq) + e- --> Fe^2+ (aq) E = 0.77 V
Fe^2+ (aq) + 2e- --> Fe (s) E = -0.44 V

Justin Chu 1G
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am
Been upvoted: 1 time

### Re: Test 2

This is because standard cell potential is not a state function so you cannot just add the E together. Rather, you have to find the G and then add those together I believe.

Jesse_torres2H
Posts: 41
Joined: Thu Jul 27, 2017 3:00 am

### Re: Test 2

I'm still unsure on this problem as well, after you find delta g how would you find the standard potential of the cell?

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

### Re: Test 2

Jesse_torres2H wrote:I'm still unsure on this problem as well, after you find delta g how would you find the standard potential of the cell?

After finding the delta g, you can do Hess' Law by adding the two to get the final overall reaction Gibbs Free Energy. Then using the equation G = -nEF, you can get the potential.

Kelly Kiremidjian 1C
Posts: 62
Joined: Fri Sep 29, 2017 7:04 am

### Re: Test 2

You would have to find delta G for both half reactions and then add them to find delta G of the entire reaction. Once you have that you can solve for E (standard potential of cell). This problem is very similar to 14.27 if you have the solutions manual