Question

Calculate the theoretical potential of the following cells. Indicate whether the reaction will proceed spontaneously in the direction considered (oxidation on the left, reduction on the right) or whether an external voltage source is needed to force this reaction to occur.

a. Pb ∣∣ Pb²⁺ (0.210M) ∥ Cd²⁺ (0.0680M) ∣∣ Cd
(EPb²⁺/Pb0 = −0.126 V, ECd²⁺/Cd0 = −0.403 V)
Potential = ____V

Answer 1

The theoretical potential of the Pb/Cd cell, calculated using their standard reduction potentials, is -0.277 V. Since this potential is negative, an external voltage source is required for the reaction to proceed in the given direction.

Step-by-step explanation:

To calculate the theoretical potential of the cell, we can use the provided standard reduction potentials for Pb and Cd. The standard cell potential (Eocell) can be calculated using the formula: Eocell = Eocathode - Eoanode. We will consider the Pb2+/Pb couple as the anode and the Cd2+/Cd couple as the cathode, as Cd has a lower (more negative) standard potential and will therefore undergo reduction.

The standard cell potential for the cell without considering concentration changes is:

Eocell = EoCd2+/Cd - EoPb2+/Pb
= (−0.403 V) - (−0.126 V)
= −0.277 V

Since the cell potential is negative, an external voltage source is necessary for the reaction to proceed in the direction given (oxidation of Pb and reduction of Cd).