Question

Study the flowchart and identify P, Q, R, and A. ​

Answer 1

Ammonia is a weak base and it combines with HCl to form ammonium chloride, ${NH}_{4}Cl$. The dissolving of ammonia in water forms a basic solution. A small amount of the dissolved ammonia reacts with water to form ammonium hydroxide ${NH}_{4}OH$, which dissociates into ammonium and hydroxide ions. Ammonium hydroxide reacts with soluble metal salts and gives insoluble precipitates of metallic hydroxides.​ When ammonium hydroxide is added to the aqueous solution of ferric chloride then a brown precipitate of iron hydroxide is formed. Heating copper oxide in presence of ammonia results in the change in colour of copper oxide from black to reddish brown. Ammonia reacts with copper oxide to produce nitrogen, copper and water.

The chemical reactions involved in the following flowchart are:

1. Reaction of ammonia with dil. Hydrochloric acid

${NH}_3$ (g) + HCl(g) → ${NH}_{4}Cl$ (g)

2. Reaction of ammonia with water.

${NH}_3$ (g) + $H_{2}O$ (l) → ${NH}_{4}OH$ (aq)

3. Reaction of ammonium hydroxide with metal salt( ${FeCl}_3$ )

${3NH}_{4}OH$ (aq) + ${FeCl}_3$ (s) → ${Fe\left(OH\right)}_3$ (s) +${3NH}_{4}Cl$ (aq)
4. Reaction of ammonia with copper oxide

${2NH}_3$ (g) + 3 CuO(s) → 3 Cu(s) + $N_2$ (g) + ${3H}_{2}O$ (l)