question_answer 90)

      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 oxidizing agent. (a) Identify A, B, C and D. (b) To which group of the periodic table does this non-metal belongs?

Answer:

                      (a)Non-metal A is nitrogen gas N2 since, the percentage ofN2 in air is largest, i.e., 78%. When N2 is heated with Hg in 1:3 ratio in presence of Fe as catalyst, it forms ammonia (NH3). Thus, B is ammonia (NH3) gas. Gas B, when heated with O2, it forms nitric oxide (NO). NO further gets oxidized to NO2 by O2 of the air. Thus, C is NO2 (nitrogen dioxide). When this oxide is passed into water in the presence of air (O2), it gives nitric acidwhich acts as a strong oxidising agent. Thus, Dis nitric acid () (b) The non-metal belongs to group 15 or VA because N has 5 valence electrons (electronic configuration is 2, 5).