Question

In the following question a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given.
Assertion (A) : The pH of acid rain is less than 5.6. Reason (R) : Carbon dioxide present in the atmosphere dissolves in rain water and forms carbonic acid.

• A. Both A and R are not correct.
• B. A is not correct but R is correct.
• C. Both A and R are correct and R is the correct explanation of A.
• D. Both A and R are correct but R is not the correct explanation of A.

Answer 1

The correct option is D Both A and R are correct but R is not the correct explanation of A.

Analysing the assertion

Rain water has a pH of 5.6 due to the presence of$H^{+}$ ions formed by the reaction of rain water with carbon dioxide present in the atmosphere. When the pH of the rain water drops below 5.6, it is called acid rain. Hence, the given assertion is the correct statement.

Analysing the reason


The below reaction is involved in the formation of carbonic acid: $H_{2}O\left(l\right)+C{O}_2\left(g\right)\rightleftharpoons H_{2}C{O}_3\left(aq\right)$

$H_{2}C{O}_3\left(aq\right)\rightleftharpoons H^{+}\left(aq\right)+HC{O}_3^{-}\left(aq\right)$

Hence, reason is also correct but not correct explanation for assertion.

Hence, from the above analysis it is concluded that option (B) is the correct one i.e., both A and R are correct but R is not the correct explanation of A.