Wednesday
May 27, 2015

Homework Help: Chemistry

Posted by Chloe on Tuesday, May 14, 2013 at 2:24am.

Using your experimental data, calculate E0cell. Standard voltaic cells contain 1M solutions, but we used 0.10M solutions in all of our half cells. Use the Nernst equation to calculate the standard cell potential (E0cell) from your measured Ecell and Qrxn.

Data:
Nernst Equation: Ecell=E0cell -RT/nF ln Q

Questions:

1. I am not sure if i did the E0cell right equation, I switched the Ecell to get the E0cell..and "n" is equal to 2 moles being transfer?

I calculated:
Measured Ecell = 0.445V
Overall rxn = Cu(s)+Pb2(aq) ~ CU2+(aq) + Pb(s)
N= 2moles??

Re-arrange the equation:
E0cell = Ecell - RT/nF ln Q
E0cell = 0.445V -(8.314 j/k*mol *298K)/(2 moles * 96500 c/mole e-) ln (0.10)
= -2.30


2. Overall reaction:
3Pb(s) + 2Al 3+ (aq) ~ 3Pb2+(aq) = 2Al(s)
Measured Ecell(V) = 0.086V
N= 6moles?? (3*2 moles)

0.086V- (8.314 j/k*mol * 298K)/ (6moles * 96500 C/mole e- ) ln (0.10/0.10^6) = 0.94??

Is this right? Please help! Thank you in advance!

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