(a) Nitrogen dioxide and sulphur dioxide forms acid rain. ‘Acid rain’ is the rain water containing sulphuric acid and nitric acid.
$$HN{O_2} + 2{H_2}O + {O_2} \to 4HN{O_3}$$
$$2S{O_2} + 2{H_2}O + {O_2} \to 2{H_2}S{O_4}$$
(b) $$N{O_2}$$  and $$S{O_2}$$  act as a good reducing agent e.g. $$S{O_2}$$  reduces halogens to halogen acid $$C{l_2} + 2{H_2}O + S{O_2} \to 2HCl + {H_2}S{O_4}$$
(c) $$N{O_2}$$  and $$S{O_2}$$  both are soluble in water.
(d) $$S{O_2}$$  is used in the manufacture of sodium bisulphite $$\left( {NaHS{O_3}} \right)$$   which is used as a preservative for jams, jellies and squashes.

Phosphorus reacts with limited $$C{l_2}$$  as :
$$\eqalign{ & {P_4} + 6C{l_2} \to 4PC{l_3}\,\,\,...\left( {\text{i}} \right) \cr & PC{l_3}\,{\text{is hydrolysed as :}} \cr & \underline {PC{l_3} + 3{H_2}O \to {H_3}P{O_3}\left. { + 3HCl} \right] \times 4\,\,\,\,\,\,\,\,\,\,\,\,} ...\left( {{\text{ii}}} \right) \cr & \underline {{P_4} + 6C{l_2} + 12{H_2}O \to 4{H_3}P{O_3} + 12HCl} \cr} $$
Moles of white $${P_4} = \frac{{62}}{{124}} = 0.5\,mol$$
$$1\;mol$$  of white $${P_4}$$  produces $$ = 12\,mol$$  of $$HCl$$
$$0.5\,mol$$  of white $${P_4}$$  will produce $$12 \times 0.5 = 6\,mol$$    of $$HCl$$
Mass of $$HCl = 6 \times 36.5 = 219\,g$$

$$Ba{\left( {{N_3}} \right)_2} \to Ba + 3{N_2}$$

When orthophosphoric acid $$\left( {{H_3}P{O_4}} \right)$$   is heated and dehydration takes place. It form metaphosphoric acid $$\left( {HP{O_3}} \right).$$
\[{{H}_{3}}P{{O}_{4}}\xrightarrow[{{600}^{\circ }}C]{\Delta }HP{{O}_{3}}+{{H}_{2}}O\]

$$CO$$  react with haemoglobin, forms carboxy haemoglobin and stopes the supply of $${O_2}$$

$$Si{O_2}$$  is attacked by $$HF$$  and $$NaOH$$  but not by chemicals under normal conditions.

Both $$BrO_2^ - \left( {35 + 2 \times 8 + 1 = 52} \right)$$      and $$BrF_2^ + \left( {35 + 2 \times 9 - 1 = 52} \right)$$      have 52 electrons.

$$Sb{H_3}$$  will act as strongest reducing agent as it has lowest bond dissociation energy and $$Sb-H$$  bond is weaker.

The fertilizer ammonium sulphate is a salt of weak base and strong acid, thus its aqueous solution is acidic, so it produces acidity.

Electron affinity of $$Cl$$  is maximum. The correct trend is $$Cl > F > Br > I.$$