Chapter 21, Problem 67A

Interpretation Introduction

Interpretation: If there is more than one reaction possible at an electrode, the reason for a reaction takes place needs to be explained.

Concept Introduction: In an electrochemical cell, oxidation occurs at the anode and reduction at the cathode. Here, species that undergo oxidation must have lower reduction electrode potential as compared to the species that undergo reduction.

Explanation of Solution

If at any electrode there is the possibility of two reactions, it can be determined which reaction takes place. First, it needs to be checked if oxidation and reduction are taking place at the electrode. For an anode where oxidation takes place, the reduction electrode potentials of two reactions can be compared. The reaction with low reduction electrode potential will be favored at the anode. Similarly, for the cathode where reduction takes place, the reduction electrode potentials are compared such that, the reaction with a higher reduction electrode potential will be favored. Thus, by comparing the reduction electrode potential of two possible reactions, the reaction that takes place in the electrode can be determined.