Atoms A and X are fictional atoms. Suppose that the standard potential for the reduction of X^2 + is + 0.51 V, and the standard potential for the reduction of A^2 + is - 0.33. Find the standard potential for an electrochemical cell with the cell reaction that follows.

While the reaction is not shown, based on those atoms and reduction potentials, the only reasonable favorable equation we can form is:

A (2+) + X - > A + X (2+)

The standard reduction potential for the cell is the cathode's reduction potential minus the anode's reduction potential, or 0.51 - (-0.33) = 0.84.