Chapter 8, Problem 8.30QP

Interpretation Introduction

Interpretation:

The reason for ammonia acts as Bronsted-Lowry base and not Arrhenius base has to be explained.

Concept Introduction:

According to Arrhenius theory, a base dissolves in water, it dissociates to produce hydroxide ions (${\text{OH}}^{-}$).  For example, sodium hydroxide dissociates in aqueous solution as given below.

    ${\text{NaOH}}_{\text{(aq)}}\underset{}{\to }{\text{ Na}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$

According to Bronsted-Lowry theory, a base is a proton acceptor.  For example, ammonia in aqueous solution accepts a proton from water, which results in formation of hydroxide ion.

    ${\text{NH}}_{\text{3}}{}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\to {\text{ NH}}_{\text{4}}{{}^{\text{+}}}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$