When the pH of rain water is above 5.6, then it is called acid rain.
I got this question in a national level competition.
This intriguing question originated from Environmental Chemistry in section Environmental Chemistry of Chemistry – Class 11
Select the correct answer from above options
Interview Questions and Answers, Database Interview Questions and Answers for Freshers and Experience
The correct answer is (b) False
The explanation is: On the pH scale, 7 is neutral; below 7 is said to be acidic and above 7 is said to be alkaline. Rain water normally 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 rain water falls below 5.6, then it is called as acid rain.
H2O (l) + CO2 (g)→ H2CO3 (aq)
H2CO3 (aq) → H^+ (aq) + HCO3^–(aq)