The rechargeable nickel-cadmium cell is used to power small appliances such as portable computers. When the cell is being used, the electrode reactions are represented by the following equations.
NiO2(s) + 2H2O(l) + 2e → Ni(OH)2(s) + 2OH-(aq)
Cd(s) + 2OH-(aq) → Cd(OH)2(s) + 2e
Which of the following occurs during the recharging of the nickel-cadmium cell?
I cadmium is deposited on the negative electrode
II the pH of the electrolyte increases
III the direction of electron ß ow in the external circuit is from the anode to the cathode
A. I only
B. I and II only
C. II and III only
D. I and III only
Solution
A galvanic cell consists of one half cell that is made up of an inert graphite electrode in a solution containing 1.0 M Fe2+(aq) and 1.0 M Fe3+(aq) at 25°C.
Which one of the following could be used as the second half cell so that the polarity of the electrode in this second half cell is positive?
A. a lead electrode in a solution of 1.0 M Pb2+(aq)
B. a silver electrode in a solution of 1.0 M Ag+(aq)
C. an iron electrode in a solution of 1.0 M Fe2+(aq)
D. an inert graphite electrode in a solution of 1.0 M Br-(aq)
Solution
