Is rain acidic or alkaline

Answer 1

Unpolluted rain should be neutral but many pollutants are acidic (oxides, dioxides and trioxides of Sulphur and Nitrogen in particular). These can become dissolved in rainwater it cause it to become acidic.

Answer 2

Rain is naturally slightly acidic, with an average pH of around 5.6 due to the presence of carbon dioxide in the atmosphere. When carbon dioxide combines with water, it forms carbonic acid, which lowers the pH of rain.