The unpolluted natural rainwater is slightly acidic due to the reaction of rain water with:
Correct answer: C. Carbon dioxide
- A. Sulphur dioxide
- B. Oxides of nitrogen
- C. Carbon dioxide
- D. Hydrogen present in air
Explanation
Unpolluted rain has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a weak acid. Also note that unpolluted air would not have A and B, hence C is the correct choice.
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