Question

question 24 of 30
which reaction occurs at the cathode of a galvanic cell that has an aluminum electrode in an electrolyte with aluminum ions and copper electrode in an electrolyte with copper ions? the reduction potential for the reduction of cu²⁺ = 0.34 v. the reduction potential for the reduction of al³⁺ = -1.68 v.
a. al³⁺(aq) + 3e⁻ → al(s)
b. cu(s) → cu²⁺(aq) + 2e⁻
c. cu²⁺(aq) + 2e⁻ → cu(s)
d. al(s) → al³⁺(aq) + 3e⁻

Explanation:

Step1: Recall cathode reaction principle

In a galvanic cell, reduction occurs at the cathode. The half - reaction with the more positive reduction potential will occur at the cathode.

Step2: Compare reduction potentials

The reduction potential of $\ce{Cu^{2+}}$ is $E^{\circ}_{Cu^{2+}/Cu}= 0.34\ V$ and for $\ce{Al^{3+}}$ is $E^{\circ}_{Al^{3+}/Al}=- 1.68\ V$. Since $0.34\ V>-1.68\ V$, the $\ce{Cu^{2+}}$ reduction will occur at the cathode.

Step3: Identify cathode reaction

The reduction of $\ce{Cu^{2+}}$ to $\ce{Cu}$ is $\ce{Cu^{2+}(aq) + 2e^{-}\to Cu(s)}$.

Answer:

C. $\ce{Cu^{2+}(aq) + 2e^{-}\to Cu(s)}$