Question

13. Which of the following causes acid rain?

• A. Carbon monoxide
• B. Water vapour
• C. Sulphur dioxide
• D. All of these

Answer 1

The correct option is C

Sulphur dioxide

Explanation:

(C) Acid rain:

Ordinary water is slightly acidic (pH 5.6) because a portion of carbon dioxide gas present in the air gets dissolved in water as carbonic acid $({\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}={\mathrm{H}}_2{\mathrm{CO}}_3)$. But rainwater containing an excess amount of dissolved acid is called acid rain. In fact, acid rain is mainly a mixture of ${\mathrm{H}}_2{\mathrm{SO}}_4,{\mathrm{HNO}}_3,\mathrm{and}\mathrm{HCI}$. The pH of such rainwater generally lies in the range of 5.6 to 3.5. The proportion of the above acids in the rainwater of different localities depends upon the quantities of sulphur dioxide (SO₂), nitrogen oxides (NO,) and hydrogen chloride (HCI) present in the air of that particular locality.

Conclusion: Thus, option (C) is the correct answer.