Chapter 8.3, Problem 2RQ

Interpretation Introduction

Interpretation :

The reason for the precipitation reactions to be called double displacement reactions must be explained.

Concept Introduction :

In a precipitation reaction an insoluble salt is produced from two soluble salts.

Answer to Problem 2RQ

Precipitation reactions are also called double displacement reaction as exchange of ions between two soluble salts take place to form a precipitate which is an insoluble salt.

Explanation of Solution

A chemical reaction involving precipitation is shown below.

  ${\text{NaCl(aq)+AgNO}}_{\text{3}}\text{(aq)}\to {\text{AgCl(s)+NaNO}}_3\text{(aq)}\text{.}$

In this reaction two soluble salts NaCl and AgNO₃ react to produce the precipitate of AgCl. Here dissociation of both NaCl and AgNO₃ takes place before the precipitate of AgCl is formed.

Thus a precipitation reaction is also a double decomposition reaction.