Why is normal, unpolluted rain water acidic?

1 Answer
anor277
Jan 5, 2017

Because of the presence of acidic oxides.

Explanation:

The atmosphere contains significant concentrations of acidic oxides: #CO_2; NO; SO_2#. All of these can combine with water to form acids: #H_2CO_3; H_2SO_3; HNO_2#. While these are weak acids, they do reduce the #pH# of rainwater to give values between #5-6#.

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