Solved 2022 Semester 2 Question Paper ICSE Class 10 Chemistry — Question 7

(a) Dry ammonia gas reacts with oxygen in the presence of platinum (catalyst) to produce nitric oxide (NO), water and heat. Nitric oxide (NO) produced is oxidised to nitrogen dioxide (NO₂) and reddish brown vapours are seen in the flask. As the reaction is exothermic, so the platinum (catalyst) continues to glow even after the heating is discontinued.
4NH₃ + 5O₂ $\xrightarrow[800 \degree \text{C}]{\text{Pt.}}$ 6H₂O + 4NO↑ + Δ
2NO + O₂ ⟶ 2NO₂

(b) Colourless ammonia gas reacts with greenish yellow chlorine gas in excess producing hydrogen chloride and a yellow explosive liquid (nitrogen trichloride).
NH₃ + 3Cl₂ [excess] ⟶ 3HCl + NCl₃

(c) Carbon reacts with hot concentrated nitric acid producing carbon dioxide, water and reddish brown fumes of nitrogen dioxide are evolved.
C + 4HNO₃ ⟶ CO₂ + 2H₂O + 4NO₂