What would you observe 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?
(a) HCl is acidic in nature. So, when the Hydrogen chloride solution is introduced to a blue litmus. Then, blue litmus will turn into red showing the acidic nature of the Hydrogen chloride gas.
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 in the forms of a solution or the litmus will be moist.
(b) When NH3 reacts with water, NH4OH(ammonium hydroxide) is formed which is a base and it contains NH4+ ion and OH− ion. Since basic ion is present, hence it changes the red litmus paper blue.
(c)Turn red litmus paper blue