Electroplating gold onto zinc

[Cramster]

Similar questions have been asked before but I need some quick clarification from you physics/chemistry gurus out there. Please correct me if I'm wrong:

If I want to plate silver onto zinc I can use an electrolytic cell. In this case the zinc ions, silver ions, silver anode, and zinc cathode are all in the same solution.

1. Since the silver electrode is the anode in the electrolytic cell it is oxidized and more silver goes into solution.
2. Either zinc or silver ions could potentially get reduced at the cathode thereby plating onto it but the silver with a reduction potential of 0.8 is more likley than the zinc with a reduction potential of -0.76 to get reduced.
3. Finally if you calculate the electric potential for this "reaction" I get zero since the zinc doesn't play a part and if you sum the reduction potential of silver and the oxidation potential of silver you get zero. I'm guessing this is why we need the energy from the batter because without it the reaction is already at equilibrium and won't progress?

I know it's really long but I would really appreciate any insight. I've been killing myself over electrochemistry all day today

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[MCAT4life]

In a electrolytic cell I think of it as trying to drive a reaction against the spontaneous reaction. So you are trying to oxidize what typically would get reduced or reduce what is typically oxidized.

Silver with more reductive potential would typically get reduced/ while zinc would typically get oxidized. (this is based on a spontaneous reaction such as a galvanic cell)
(So in an electrolytic cell your going against what Silver/Zinc would typically do that is Silver is oxidized, Zinc is reduced)

Electrons always flow from the Anode to the Cathode. So here you are trying to go against the spontaneous reaction by plating the silver onto zinc, inorder to drive against the spontaneous reaction, you would have to use the voltage input. to drive electrons in the opposite direction.

Your (0.8 , -0.76) potentials would sum to be (-.8 + (-0.76) = -1.56 Based on E = Ered + Eox. Since this is a negative number if you plus this E into Delta G = -nfE you can see that delta G is a positive number making this reaction none spontaneous as written, therefore another reason why you would need the battery to drive the reaction.