Question

# A non-metal A which is the largest constituent of air, when heated with H2 in 1:3 ratio in the presence of a 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?

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## (a) Identification of A, B, C, and D(i) A- Non-metal A is Nitrogen (N) because Nitrogen gas (N2) comprises 78 % of the air and is the largest constituent of air.(ii) B- Gas B is Ammonia (NH3). It is formed when Nitrogen reacts with Hydrogen (H) in the ratio 1:3 in the presence of a catalyst called Iron (Fe)$\underset{\left(\mathrm{Nitrogen}\right)}{{\mathrm{N}}_{2}\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Hydrogen}\right)}{3{\mathrm{H}}_{2}\left(\mathrm{g}\right)}\underset{\mathrm{Fe}/\mathrm{Mo}}{\overset{400-450°\mathrm{C},200\mathrm{atm}}{⇌}}\underset{\left(\mathrm{Ammonia}\right)}{2{\mathrm{NH}}_{3}\left(\mathrm{g}\right)}$(iii) C is Nitrogen dioxide (NO2)$\underset{\left(\mathrm{Nitrogen}\right)}{{\mathrm{N}}_{2}\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{2{\mathrm{O}}_{2}\left(\mathrm{g}\right)}\to \underset{\left(\mathrm{Nitrogen}\mathrm{dioxide}\right)}{2{\mathrm{NO}}_{2}\left(\mathrm{g}\right)}$(iv) D is Nitric acid (HNO3) which acts as an oxidizing agent.$\underset{\left(\mathrm{Nitrogen}\mathrm{dioxide}\right)}{3{\mathrm{NO}}_{2}\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\left(\mathrm{Nitric}\mathrm{acid}\right)}{2{\mathrm{HNO}}_{3}\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Nitric}\mathrm{oxide}\right)}{\mathrm{NO}\left(\mathrm{aq}\right)}$(b) Group of the non-metal A in the periodic tableNitrogen belongs to group 15The Atomic number of Nitrogen= 7The electronic configuration of Nitrogen is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{3}$As the last electron enters in p-subshell, so it is a p block element.For the p block, the group is calculated as$=12+\mathrm{number}\mathrm{of}\mathrm{electrons}\mathrm{in}\mathrm{the}\mathrm{valence}\mathrm{p}-\mathrm{subshell}$Therefore, the group number for Nitrogen$=12+3=15$

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