Chapter 16, Problem 51A

(a)

Interpretation Introduction

Interpretation:

The behaviour of $HCl$ as acid in liquid ammonia is to be discussed.

Concept introduction:

Solvent system concept helps to identify a substance as acid or base when the solvent used in the reaction is other than water.

According to it, a substance is acid in a particular solvent if it increases the cation concentration which is produced in auto-ionization of the solvent and a substance is base in a particular solvent if it increases the anion concentration which is produced in auto-ionization of the solvent

Answer to Problem 51A

  $HCl+N{H}_3\to C{l}^{-}+N{H}_4{}^{+}$

Explanation of Solution

Ammonia is auto-ionized as:

  $2N{H}_3\to N{H}_2{}^{-}+N{H}_4{}^{+}$

Thus, the substance which increases the concentration of $N{H}_4{}^{+}$ behaves as acid and which increases the concentration of $N{H}_2{}^{-}$ behaves as base.

Therefore, $HCl$ behaves as acid.

(b)

Interpretation Introduction

Interpretation:

The behaviour of OH- as base in liquid ammonia is to be discussed.

Concept introduction:

Solvent system concept helps to identify a substance as acid or base when the solvent used in the reaction is other than water.

According to it, a substance is acid in a particular solvent if it increases the cation concentration which is produced in auto-ionization of the solvent and a substance is base in a particular solvent if it increases the anion concentration which is produced in auto-ionization of the solvent

Answer to Problem 51A

  $O{H}^{-}+N{H}_3\to N{H}_2{}^{-}+H_{2}O$

Explanation of Solution

Ammonia is auto-ionized as:

  $2N{H}_3\to N{H}_2{}^{-}+N{H}_4{}^{+}$

Thus, the substance which increases the concentration of $N{H}_4{}^{+}$ behaves as acid and which increases the concentration of $N{H}_2{}^{-}$ behaves as base.

Therefore, $O{H}^{-}$ behaves as base.