May 5, 2015

Homework Help: chemistry

Posted by fenerbahce on Friday, July 20, 2012 at 10:02am.

How do you calculate the theoretical cell voltage?

1) Zn|Zn^+2 (1M)| Cu|Cu^+2 (1M)

okay so by looking at example this example

Calculate the emf (voltage) for the following reaction:
Zn(s) + Fe2+ → Zn2+ + Fe(s)
Write the 2 half reactions:
Zn(s) → Zn2+ + 2e
Fe2+ +2e → Fe(s)

look up the standard electrode potentials in the table above
Zn2+ + 2e → Zn Eo = -0.76V
This equation needs to be reversed, so the sign of Eo will also be reversed.
Zn(s) → Zn2+ + 2e Eo = +0.76V
Fe2+ +2e → Fe(s) Eo = -0.41V

Add the two equations together:
Zn(s) → Zn2+ + 2e Eo = +0.76V
Fe2+ + 2e → Fe(s) Eo = -0.41V
Zn(s) + Fe2+ → Zn2+ + Fe(s) Eocell = +0.76 + (-0.41) = +0.35V

I came up with the answer: 1.11

So am I on the right track?

for the first one they more have 1 M

but for this question:

Cu|Cu^+2 (1M) Cu|Cu^+2(0.1 M)

see how one has 1M and the other 0.1M will that make a difference in the calculation thank you.

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