Chapter 21.2, Problem 9SP

Interpretation Introduction

Interpretation: Whether the given redox reaction will occur spontaneously or not needs to be identified.

Concept Introduction: Whether a metal can reduce other metals from its solution or not can be determined from its reduction electrode potential. The metal with a high reduction electrode potential cannot reduce the metal with a low reduction electrode potential.

Explanation of Solution

The given redox reaction is as follows:

  ${\text{Co}}^{2+}\left(aq\right)+\text{Fe}\left(s\right)\to {\text{Fe}}^{2+}\left(aq\right)+\text{Co}\left(s\right)$

The two half-reactions are as follows:

  $\begin{array}{l}{\text{Co}}^{2+}\left(aq\right)+2e\to \text{Co}\left(s\right)\\ \text{Fe}\left(s\right)\to {\text{Fe}}^{2+}\left(aq\right)+2e\end{array}$

Here, the reduction of Co and oxidation of Fe take place. Whether the given reaction is spontaneous or not can be determined by checking the reduction electrode potentials of the two reactions.

The metal with more reduction electrode potential value can be easily reduced and the metal with less reduction electrode potential value can be easily oxidized.

The reduction electrode potential of the two half-reactions are as follows:

  $\begin{array}{l}{\text{Co}}^{2+}\left(aq\right)+2e\to \text{Co}\left(s\right)-\text{0}\text{.28 V}\\ \text{Fe}\left(s\right)\to {\text{Fe}}^{2+}\left(aq\right)+2e-\text{0}\text{.44 V}\end{array}$

Here, Co has more reduction electrode potential thus, it will undergo reduction, and oxidation of Fe takes place.

Thus, the given redox reaction will occur spontaneously.