Chemistry - how to calculate standard cell potential?

Calculate the standard cell potential of a cell composed of the half -cells Ni/Ni2+ and Cu/Cu2+. Write the half-cell reactions for the anode and cathode processes and the cell reaction.

Answer:
Some shortforms to help you:

1) LEO goes GER
(Losing Electrons Oxidation, Gaining Electrons Reduction)

2) OARC
(Oxidation = anode, reduction = cathode)

Step 1: Write the full equations
The two half cells you have given are:
1) Ni/Ni2+
so: Ni --> Ni2+ + 2electrons (e-)

2) Cu/Cu2+
so: Cu --> Cu2+ + 2e-

Step 2: Find the Eo values in a table (standard REDUCTION potentials

Ni2+ + 2e- --> Ni Eo = -0.257V
Cu2+ + 2e- --> Cu Eo = 0.340V

Step 3: Calculate the standard cell potential

I am assuming here that the teachers wants you to calculate the SPONTANEOUS cell potential (i.e. a positive value)

The formula for calculating this is:
E cell = E cathode - E anode

Using the shortforms I mentioned earlier:
Cathode= reduction
Anode = oxidation

So we have:
Anode: Ni --> Ni2+ + 2e- Eo = -0.257V
Cathode: Cu2+ + 2e- --> Cu Eo= 0.340V

Ecell = Ecath - Eanode
= 0.340V - (-0.257V)
= 0.597V

NOTE:
you can flip either of the two equations to make it read as a reduction or oxidation. Just leave the cell potentials as you found them in the table, and use the formula as I did. You want to have a positive value, which means this is the reaction that occurs spontaneously, so look at the Eo values in the table and determine which one MUST be the cathode and which one MUST be the anode, so that you end up with a positive value.

BF
4th yr Chem Major
U of O (Canada)

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Chemistry - how to calculate standard cell potential?

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