question_answer

A non-metal P which is the largest constituent of air. When heated with H2 in 1 : 3 ratio in the presence of catalyst (Fe) gives a gas Q. On heating with O2, it gives an oxide R. If this oxide is passed into water in the presence of air, it gives an acid S which acts as a strong oxidising agent. (a) Identify P, Q, R and S. (b) To which group of Periodic Table does this non-metal belong?                                 Or Give reasons for the following (a) Silver and copper lose their shine when they are exposed to air. Name the substance formed on their surface in each case. (b) Tarnished copper vessels are cleaned with tamarind juice. (c) Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air.  

Answer:

(a) Nitrogen  is largest constituent of air, when heated with hydrogen  in the ratio of 1 : 3 in the presence of catalyst (Fe) gives a gas .                                                          (1) Nitrogen reacts with oxygen on heating to form nitrogen monoxide (R), which gets oxidised in the presence of  to nitrogen dioxide. Nitrogen dioxide dissolves in water in the presence of oxygen to form nitric acid which is an oxidising agent.                                                                (1)                                                       (1) P is Q is , R is NO and S is .      (1) (b) It belongs to group 15.                                                  (1)                                 Or (a) These metals get corroded. Silver forms black silver sulphide  and copper form greenish layer of basic copper carbonate                                                                  (2) (b) Tamarind contains acid which reacts with basic copper carbonate and product gets dissolved and removed from copper vessel.                                                              (1½ ) (c) Aluminium forms oxide layer on its surface which does not further react with air.  (1½)