2Ag+ + Zn = 2Ag + Zn2+?

Question

2Ag+ + Zn = 2Ag + Zn2+

Calculate the standard free energy change in kJ/mol for the above cell reaction

Answer 1

Ok, here are the steps:
1) get half reactions:
Ag+ + e- --> Ag (s) E(standard) = .7993 V
Zn2+ + 2e- --> Zn (s) E(standard) = -.762 V

2) add energies
E(total) = Ecath - Eanode
=.7993-(-.762) = 1.56 volts

3) 1 volt = 1 joule/coulomb
1.56v * (9.649E4 coulombs/mole) = 1.50E5 Joules
this is equal to 0.15 kJ/mol

Answer 2

Care! E is not energy, it is energy PER COULOMB. that's what voltage is.

So energy = E x charge = E x 2 (2-electron process) x Faraday's constant.