$i.$ $4 NO _2( g )+ O _2( g )+2 H _2 O (\ell) \rightarrow 4 HNO _3( aq )$

$SO _2$ \& $NO _2$ have major contribution in acid rain

$ii.$ $CO _2, CH _4, O _3, CFC$ are responsible for global warming

$iii.$

$H _2 O (\ell)+ CO _2( g ) \rightleftharpoons H _2 CO _3 \text { (aq.) }$

$\left. H _2 CO _3 \text { (aq.) } \rightleftharpoons H ^{+} \text {(aq. }\right)+ HCo _3^{-} \text {(aq.) }$

Rain water has $pH$ of 5.6 due to the Presence of $H ^{+}$ions formed by the reaction of rain water with $CO _2$

$iv.$ Phosphates present in fertilizers contribution for Eutrophication (Process in which nutrient enriched water bodies support a dense plant population, which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.)