CHEMISTRY COMMUNITY

Predict the potential of each of the following cells:
(a) Pt(s) | H2(g, 1.0 bar) | HCl(aq, 0.075 mol?L21) || HCl(aq, 1.0 mol?L21) | H2(g, 1.0 bar) | Pt(s).
How do you find the half reactions for this problem?

The left side of the cell diagram corresponds to the anode, so you know oxidation will occur here. Since the overall molecule of HCl is neutral, this must mean that the H has a charge of +1 and the Cl has a charge of -1. Since HCl is a strong acid and completely dissociates, we can assume that H2 is being oxidized to H+ at the anode and that the Cl- is just a spectator ion. The reverse is true at the cathode, where H+ is being reduced to 0 in H2.