Question

question 22 of 30
which reaction occurs at the cathode of a galvanic cell that has the following: an aluminum electrode in an electrolyte with aluminum ions and a zinc electrode in an electrolyte with zinc ions? the reduction potential for the reduction of al³⁺ = -1.68 v. the reduction potential for the reduction of zn²⁺ = -0.76 v.
a. zn²⁺(aq) + 2e⁻ → zn(s)
b. zn(s) → zn²⁺(aq) + 2e⁻
c. al³⁺(aq) + 3e⁻ → al(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

Given $E^0_{Al^{3 + }/Al}=-1.68\ V$ and $E^0_{Zn^{2 + }/Zn}=-0.76\ V$. Since $- 0.76\ V>-1.68\ V$, the reduction of $Zn^{2+}$ will occur at the cathode.

Step3: Identify the cathode reaction

The reduction half - reaction for $Zn^{2+}$ is $Zn^{2 + }(aq)+2e^-\to Zn(s)$.

Answer:

A. $Zn^{2+}(aq)+2e^-\to Zn(s)$