A-Level Redox, electrode potentials and electrolysis: worked solution

Question

A dilute solution of potassium iodide is subjected to electrolysis using inert carbon (graphite) electrodes. Give the balanced half-equation for the process that takes place at each electrode. At the positive electrode (anode): At the negative electrode (cathode):

Dilute aqueous KI, inert graphite electrodes. Anode (positive electrode, oxidation): iodide is discharged in preference (halide present, and I^- is readily oxidised) to give iodine: 2I^- -> I2 + 2e^- Cathode (negative electrode, reduction): in dilute solution H^+ from water is discharged in preference to K^+ (K is very reactive), giving hydrogen: 2H2O + 2e^- -> H2 + 2OH^- (equivalently 2H^+ + 2e^- -> H2)