Question

A white crystal compound N when warmed with concentrated sulphuric acid gives a gas that turns fumes into ammonia. When N is warmed with sodium hydroxide solution gas is evolved which turns moist red litmus paper blue.

Identify the solid N and name the two gases that evolved in each case.

Answer 1

Step 1:

• When Ammonium chloride $\left({\mathrm{NH}}_4\mathrm{Cl}\right)$white crystalline salt reacts with concentrated Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ gives a gas that turns fumes into Ammonia also Hydrochloric acid $\left(\mathrm{HCl}\right)$
• The chemical Reaction is as follows.

$\underset{\mathrm{Ammonium}\mathrm{chloride}}{2{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{l}\right)}\to \underset{\mathrm{Ammonium}\mathrm{sulfate}}{{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{g}\right)}$

Step: 2: The reaction between Ammonium chloride with Sodium hydroxide:

• When Ammonium chloride reacts with Sodium hydroxide gives Ammonia $\left({\mathrm{NH}}_3\right)$, Water $\left({\mathrm{H}}_2\mathrm{O}\right)$, and Sodium chloride $\left(\mathrm{NaCl}\right)$. Here, the solution of ammonia in water turns red litmus paper blue.
• The chemical reaction is as follows.

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

Thus, Solid “N” is $\left({\mathrm{NH}}_4\mathrm{Cl}\right)$and two gases that are involved in step 1 and step 2 are Hydrochloric acid $\left(\mathrm{HCl}\right)$ and Ammonia $\left({\mathrm{NH}}_3\right)$