How does rain water have a higher pH then tap water and exactly does that mean?

Question

How does rain water have a higher pH then tap water and exactly does that mean?

In: Chemistry

Answer 1

Sulfur aerosols mostly. Sulfur dioxide (SO2, which we get a ton of from burning coal) reacts with oxygen and water to create H2SO4. This breaks down into a free hydrogen ion and sulfate (HSO4). pH is a measure of how many free hydrogens there are, so through this reaction, the concentration of hydrogen ions increases very quickly in clouds (because droplets have a ton of surface area, and surface area increases the rate of reaction). The water is acidic now.