Lets say we want the activity coefficient of $\ce{Cu^{2+}}$ ions in solution. Would we simply setup one half cell of a $\ce{Cu}$ electrode in a known concentration of $\ce{CuSO4}$ and then connect this to a Standard Hydrogen Electrode.
Using the standard electrode potential of the reaction $\ce{Cu^{2+} + 2e- -> Cu}$ and the Nernst equation could we determine the activity coefficient of $\ce{Cu^{2+}}$ ions ?
Is this all I would need to do ?