Increasing the concentration of Cu²⁺ ions in a galvanic cell will cause the cell potential to increase, as it promotes the reduction half-reaction of Cu²⁺ ions to Cu(s) and generates a higher potential.
Step-by-step explanation:
The question asks which change to a galvanic cell involving Pb(s) and Cu(s) would cause the cell potential to increase. According to the Nernst equation, the cell potential depends on the concentrations of the ions in the half-cells. Increasing the concentration of the Cu²⁺ ions will increase the cell potential, as it would push the equilibrium more towards the reduction of Cu²⁺ ions to Cu(s), thereby generating a higher potential. Changes to the mass of the Pb(s) electrode do not affect the cell potential because the cell potential is not dependent on the mass of the solid electrodes but on the concentrations of the aqueous ions involved in the half-reactions.