What is the pH of rainwater? Is the pH suitable for drinking?

The technical definition of pH is that it is a measure of the activity of the hydrogen ion ( H⁺ ) is essentially a measure of acidity. The pH scale ranges from 0 -14. In the scale the reading `7' denotes the neutral point. A substance can be rated acidic or basic depending on its pH value. It will be rated as acidic if it has a pH of less than 7 and basic if it is greater.

 Normal rainwater has a pH of 5.6 (slightly acidic). This is because it is exposed to the carbon dioxide in the atmosphere. The carbon dioxide gets dissolved in the rainwater and forms carbonic acid (H₂CO₃₎  Rainwater with ph value below 5.6 is considered as acid rain. There are both natural and non-natural sources of materials that cause pH of rain water to change. Increasing pollution results in acid rains. The primary air pollutants are sulphur dioxide and nitrogen oxide. These pollutants are released into the air due to many factors and burning fossil fuels (ex: coal) is one of the major causes.

 Generally rainwater is pure and potable. The pH of drinking water falls in the range of 6.5- 8. Therefore if the pH of rainwater centres around this value it is fit for drinking. Also the pH of rainwater differs from place to place. This is due to heavy pollution in one area and clean air in another. In the present scenario urbanization has increased its acidity. But in case of rains whose pH generally falls around 5.6, it is potable, but it will be slightly acidic and corrosive. But in and around cities and other industrially developed areas where the pH of rainwater tends to fall drastically, rainfall is highly acidic and the water thereby becomes unfit for consumption. Courtesy : The Hindu