The lower a substance's pH (less than 7), the more acidic it is; the higher a substance's pH (greater than 7), the more alkaline it is. Normal rain has a pH of about 5.6; it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid. Acid rain usually has a pH between 4.2 and 4.4.
At what pH is acid rain?
Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced from power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0.
Where does the pH range for acid rain begin?
Carbon dioxide (CO22) in the atmosphere makes all rain slightly acidic because carbon dioxide and water combine to form carbonic acid, commonly known as carbonated water. The pH of normal rainwater ranges from 5.5 to 5.6, while most acid rain has a pH value of 4.0 to 4.6.
