The half-cell is a chamber in the voltaic cell where one half-cell is the site of the oxidation reaction and the other half-cell is the site of the reduction reaction. Type the half-cell reaction that takes place at the anode for the cobalt-silver voltaic cell. Indicate the physical states of atoms and ions using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively. Use (aq) for an aqueous solution. Do not include phases for electrons. Express your answer as a chemical equation.