Question

Name a gas which is alkaline in nature.

Answer 1

Ammonia (NH₃) gas is alkaline in nature. Ammonia has a pungent smell.

The evolution of ammonia gas occurs as follows:

$$\begin{gathered} {\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to {\mathrm{NH}}_3\left(\mathrm{g}\right)+\mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ (\mathrm{Ammonium}(\mathrm{Sodium}\left(\mathrm{Ammonia}\right)(\mathrm{Sodium}(\mathrm{Water}) \\ \mathrm{chloride})\mathrm{hydroxide})\mathrm{chloride} \end{gathered}$$

Gas released above turns moist red litmus paper blue because ammonia reacts with water (from moist litmus paper) to form Ammonium hydroxide (NH₄OH).

Ammonium hydroxide splits into the ions as shown below.

$$\begin{gathered} {\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)\to \mathrm{NH}{}_4{}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right) \\ (\mathrm{Ammonium}\mathrm{hydroxide})(\mathrm{Ammonium}\mathrm{ions})(\mathrm{Hydroxide}\mathrm{ions}) \end{gathered}$$

The hydroxide ions thus released are responsible for the basic nature of ammonia.

This indicates that the gas is alkaline in nature as bases turn moist red litmus paper blue.

In addition, acids turn moist blue litmus paper red.