Standard half-cell potentials

Problem Example 1
Find the standard potential of the cell

Cu(s) | Cu²⁺ || Cl^– | AgCl(s) | Ag(s)

and predict the direction of electron flow when the two electrodes are connected.
Solution: The net reaction corresponding to this cell will be

2 Ag(s) + 2 Cl^–(aq) + Cu²⁺(aq) → AgCl(s) + Cu(s)

Since this involves the reverse of the AgCl reduction, we must reverse the corresponding half-cell potential:

E_cell = (.337 – .222) v = .115 v

Since this potential is positive, tthe reaction will proceed to the right; electrons will be withdrawn from the copper electrode and flow through the external circuit into the silver electrode. Note carefully that in combining these half-cell potentials, we did not multiply E° the for the Cu²⁺/Cu couple by two. The reason for this will be explained later.

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