Question

A compound P is heated in a test tube with sodium hydroxide solution. A red litmus paper held at the mouth of the test tube turns blue.

Which of the following could compound P be?

विकल्प

• Zinc sulphate

• Copper sulphate

• Ferrous sulphate

• Ammonium sulphate

Answer 1

Ammonium sulphate

Explanation:

When an ammonium salt such as ammonium sulphate is heated with a strong base like sodium hydroxide, it liberates ammonia gas (NH₃). Ammonia is basic; it dissolves in moisture to form ammonium hydroxide, which turns moist red litmus paper blue. The reaction is:

\[\ce{(NH4)2SO4_{(s)} + 2NaOH_{(aq)} ->[\Delta] Na2SO4_{(aq)} + 2H2O_{(l)} + 2NH3_{(g)}}\]