Chapter 20, Problem 65A

Interpretation Introduction

Interpretation: The reason that a double replacement reaction is not a redox reaction is to be explained.

Concept introduction: The chemical reaction in which a new chemical compound is formed by the exchange of ions between reactants is a double displacement reaction.

Answer to Problem 65A

Double displacement reactions involve only ion exchange between reactants, so, it is not an example of a redox reaction.

Explanation of Solution

Redox reactions are those reactions that contain electron transfer between the reactant molecules. The oxidation number of species is also changing in the case of redox reactions.

For a double displacement reaction, there is no electron transfer between the reactants; there is only an exchange of ions I between reactants involved in the reaction.

For example,

  $Pb{\left(N{O}_3\right)}_2\left(aq\right)+2KI\left(aq\right)\to Pb{I}_2\left(s\right)+2KN{O}_3\left(aq\right)$

There is only exchanging of ions between Pb and K taking place. So, double displacement is not a redox reaction.