The nickel–cadmium cell is rechargeable. The half equations for the electrode reactions are:

Cd(OH)₂ + 2e^– → Cd + 2OH^–                             E^θ= –0.81 V

NiO₂ + 2H₂O + 2e^–  → Ni(OH)₂ + 2OH^–                E^θ= +0.49 V

a. Which of these reactions proceeds in a forward direction when electrical energy is being taken from the cell?

b. Predict the cell voltage, assuming that all conditions are standard.

c. Write an equation for the cell reaction that occurs when electrical energy is being taken from the cell.

d. Write an equation for the cell reaction that occurs when the cell is being recharged.