Q59 of 65 Page 26

A non-metal A which is the largest constituent of air, when heated with H2 in 1:3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O2 it gives an oxide C. If this oxide is passed into water in the presence of air it gives an acid D which acts as a strong oxidising agent.

(a) Identify A, B, C and D.


(b) To which group of periodic table does this non-metal belong?

The non-metal A is nitrogen (N2). It forms the largest constituent of air, i.e., 78%. When N2 is heated with H2 in 1:3 ratio in presence of iron (Fe) as catalyst, it forms ammonia gas (NH3). This is known as Haber process. Thus the gas B is ammonia. When ammonia is heated with O2, it forms nitric oxide (NO). NO further gets oxidized to NO2 by O2. Thus, oxide C is NO2 (nitrogen dioxide). When this oxide reacts with water in the presence of air (O2), it gives nitric acid. Thus acid D is nitric acid which is a strong oxidizing agent. The chemical reactions involved are as follows:


N2(g)+3H2(g)2NH3(g)


4NH3(g)+5O2(g) 4NO(g)+6H2O(g)


2NO(g)+O2(g)2NO2(g)


4NH2+2N2O+O24HNO3


(b) Nitrogen belongs to Group 15 of periodic table because nitrogen has 5 valence electrons (electronic configuration is of N is 2, 5).

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