Electrochemistry Question 1

A galvanic cell is constructed using two half-cells based on the two half-reactions represented below.

\ce{Zn^{2+}(aq) + 2e^- -> Zn(s)} \hskip{2em} E^\circ = \pu{-0.76 V}

\ce{Fe^{3+}(aq) + e^- -> Fe^{2+}(aq)} \hskip{2em} E^\circ = \pu{0.77 V}

As the cell operates, ionic species that are found in the half-cell containing the cathode include which of the following?

$\ce{Zn^{2+}(aq)}$
$\ce{Fe^{2+}(aq)}$
$\ce{Fe^{3+}(aq)}$

I only

II only

I and III

II and III

Approach

The cathode represents the electrode where reduction takes place. The half-reaction with the greater reduction potential will occur in the cathode. Therefore, the second equation $(0.77 \gt -0.76)$ will occur in the cathode. The two iron ions are present in this reaction.

Note that both ions will be present. It is unlikely that the reaction will go to completion. Equilibrium will be reached in which both ions exist.