There are two possible types of acid in acid rain. 1) The acid formed from Carbon Dioxide (from natural Carbon Dioxide in air, from man burning fossil fuels and from volcanic gasses); Carbonic Acid...
Acid rain can have a pH as low as 3. The pH is the negative logarithm of the molar concentration of the H+ ion in the solution. This means there is 1x10-3 moles of H+ ion in each liter of water.