On heating compound A gives a gas B which is constituent of air. This gas when treated with H 2 in the presence of a catalyst gives another gas C which is basic in nature. A should not be :

Step-by-step solution

Pb NO 3 2 ⟶ Δ PbO + 2 NO 2 N 2 gas is constituent of air and it produces ammonia gas (basic nature) after reacting with H 2 gas. NH 4 NO 2 ,   ( NH 4 ) 2 Cr 2 O 7   and   NaN 3   give nitrogen gas on heating but lead nitrate doesn't give nitrogen gas so it will be answer. NH 4 NO 2 ⟶ Δ N 2 + 2 H 2 O NH 4 2 Cr 2 O 7 ⟶ Δ N 2 + Cr 2 O 3 + H 2 O NaN 3 ⟶ 300 ° C 3 N 2 + 2 Na