Question

Write your observations when:

(a) blue litmus is introduced into a solution of hydrogen chloride gas.

(b) red litmus paper is introduced into a solution of ammonia in water.

(c) red litmus paper is introduced in caustic soda solution.

Answer 1

(a) HCl is acidic in nature. So, when hydrogen chloride solution is introduced to a blue litmus, it will turn into red showing the acidic nature of the hydrogen chloride.
Note: When dry gas is brought near the dry blue litmus, no effect will be observed. For the effects to be observed, either the gas should be dissolved in water or the litmus should be moist.

(b) When \(NH_3\) reacts with water, \(NH_4OH\)(ammonium hydroxide) is formed which is a base. Hence it changes the red litmus paper blue.

(c) Caustic soda solution is basic in nature and it will turn red litmus paper blue.