Chapter 8.1, Problem 4RQ

Interpretation Introduction

Interpretation :

The difference in the molecular equation and a complete ionic equation must be explained.

Concept Introduction :

Molecular equation deals with molecule whereas ionic equation deals with component ions of the reacting species and products.

Answer to Problem 4RQ

A molecular reaction represents the reactants and products in the form of molecules.

But a complete ionic equation represents the reactants and products in ionic form.

Explanation of Solution

Let’s consider the reaction between a strong acid (HNO₃) and a strong base (KOH).

  ${\text{HNO}}_{\text{3}}\text{(aq)}\to {\text{H}}^{\text{+}}{\text{(aq)+NO}}_{\text{3}}{}^{\text{-}}\text{(aq)}$ .

From the above equation it can be seen that HNO₃ is completely dissociated to produce H+ and NO₃- ions.

  $\text{KOH(aq)}\to {\text{K}}^{\text{+}}{\text{(aq)+OH}}^{\text{-}}\text{(aq)}$ .

Similarly KOH solution produces K+ and OH- ions.

As these are strong electrolytes so there is complete dissociation. No undissociated molecule can be seen.

Overall reaction will be

  $\begin{array}{l}\text{HCl(aq)+KOH(aq)}\to {\text{KCl(aq)+H}}_{\text{2}}\text{O(l)}\text{.}\\ {\text{H}}^{\text{+}}\text{(aq)}+{\text{Cl}}^{\text{-}}{\text{(aq)+K}}^{\text{+}}{\text{(aq)+OH}}^{\text{-}}\text{(aq)}\to {\text{K}}^{\text{+}}{\text{(aq)+Cl}}^{\text{-}}{\text{(aq)+H}}_{\text{2}}\text{O(l)}\text{.}\end{array}$

First equation is the molecular equation in which all the reactants and products are in the form of molecules.

In the second equation all the components ions are shown.