Question 4(iii)State one relevant observation for each of the the following reactions.(a) When hydrogen chloride gas is passed through a solution of sodium thiosulphate.(b) Concentrated sulphuric acid is added to a solution of potassium nitrate.(c) When fused lead bromide is electrolysed.

Question

Question 4(iii)State one relevant observation for each of the the following reactions.(a)	When hydrogen chloride gas is passed through a solution of sodium thiosulphate.(b)	Concentrated sulphuric acid is added to a solution of potassium nitrate.(c)	When fused lead bromide is electrolysed.

Accepted Answer

(a) When hydrogen chloride gas is passed through a solution of sodium thiosulphate a yellow precipitate of Sulphur can be seen along with water, Sodium chloride, and Sulphur dioxide gas which has a burning smell.

Na₂S₂O₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ + S ↓

(b) Nitric acid is released with a pungent odour when concentrated sulphuric acid is added to a solution of potassium nitrate.

KNO₃ + H₂SO₄ (conc.) $\xrightarrow{\lt 200 \degree\text{C}}$ KHSO₄ + HNO₃

(c) At anode, reddish brown fumes of bromine vapours are seen. At cathode, silver grey deposit of lead metal is observed.
At cathode:
Pb²⁺ + 2e^- ⟶ Pb
At anode:
Br^- ⟶ Br + e^-

Solved Sample Paper 5 — Question 7

Question 4(iii)