Question

A gas 'A' reacts with another gas 'B' in the presence of a catalyst to give a colourless gas 'C'. The gas 'C' when comes in contact with air produces a brown gas 'D'. The solution of 'A' in water turns red litmus blue. Explain the observations.

Answer 1

1. The reactions are as follows:
$4N{H}_3\left(g\right)+5O_2\left(g\right)⟶4NO\left(g\right)+6H_{2}O\left(l\right)$

A B C (Colourless gas)

Ammonia gas (A) reacts with Oxygen gas (B) to yield colourless gas of NO (C). Further, the NO gas reacts with O2 with expose to air, it becomes brown gas, NO2(D).

$2N{O}_{(}g)+O_2(g)⟶2N{O}_2(g)$

C D (brown gas)

2. Ammonia is basic in nature and it turns red litmus blue.