use the half-cell potentials to calculate δg° for the following balanced redox reaction. pb2 (aq) 2 e⁻ → pb(s) e° = -0.13 v cu2 (aq) 2 e⁻ → cu(s) e° = 0.34 v pb2 (aq) cu(s) → pb(s) cu2 (aq)