Question

The normal rain water is slightly acidic and its $pH$ value is $56$ because of which one of the following ?

• A. $CO _2+ H _2 O \rightarrow H _2 CO _3$
• B. $N _2 O _5+ H _2 O \rightarrow 2 HNO _3$
• C. $2 SO _2+ O _2+2 H _2 O \rightarrow 2 H _2 SO _4$
• D. $4 NO _2+ O _2+2 H _2 O \rightarrow 4 HNO _3$

Answer 1

Answer: (A)

$CO _2+ H _2 O \rightarrow H _2 CO _3$

Answer 2

We are aware that normally rain water has a pH of 5.6 due to the presence of H+ions formed by the reactions of rain water with carbon dioxide present in the atmosphere.
H2​O(l)+CO2​(g)⇋H2​CO3​(aq)
H2​CO3​(aq)⇋H+(aq)+HCO3−​(aq)
So , the correct option is (A) : $CO _2+ H _2 O \rightarrow H _2 CO _3$