Question

9b. State your observation for the following cases :

(v) Glass rod dipped in ammonium hydroxide is brought near the mouth of the concentrated hydrochloric acid bottle.

Answer 1

Step 1: Dense white fumes are evolved.

Ammonia gas ${\mathrm{NH}}_3$ gives dense white fumes with Hydrogen chloride HCl when a glass rod dipped in it is brought near the bottle of HCl. Following inferences can be made in this experiment:

1. Ammonia gas is alkaline due to the basicity of the nitrogen atom. Thus it reacts with acids to give salt.
2. The dense fumes observed are of white Ammonium chloride ${\mathrm{NH}}_4\mathrm{Cl}$ salt formed.
3. This test is used in the detection of Nitrogen present in a compound.

Step 2: Chemical reaction:

$$\begin{gathered} {\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{NH}}_4\mathrm{Cl}\downarrow +{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Ammonium}\mathrm{Hydrochloric}\mathrm{Ammonium}\mathrm{Water} \\ \mathrm{Hydroxide}\mathrm{acid}\mathrm{chloride} \end{gathered}$$

Final Answer: Dense white fumes of Ammonium chloride are formed.