(a) What is the action of red litmus on:
(i) Dry ammonia gas (ii) Solution of ammonia gas in water

(b)State the observations when ammonium hydroxide is added to the aqueous solution of:
(i) Ferrous sulphate (ii) Aluminium chloride.

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Solution

(a) (i) Red litmus has no action on dry ammonia gas because it does not release any hydroxyl ions (OH)^–.

(ii) When passed through water, ammonia (NH₃) is converted to ammonium hydroxide (NH₄OH). It dissociates to give hydroxyl ions (OH)^– and the solution is basic in nature. Red litmus acquires a blue colour.

(b) (i) A green precipitate of ferrous hydroxide will be formed by double decomposition reaction.
${F e S O}_{4} (a q)$ + $2 {N H}_{4} O H (a q) \to$ ${F e (O H)}_{2}$ + ${(N H}_{4})_{2} {S O}_{4} (a q)$

(ii) A white precipitate of aluminium hydroxide will be formed by double decomposition reaction.
${A l C l}_{3} (a q)$ + $3 {N H}_{4} O H (a q) \to$ ${A l (O H)}_{3}$ + $3 {N H}_{4} C l (a q)$

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What is the action of litmus on :
(a) Dry ammonia gas (b) Solution of ammonia gas in water

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