Final answer:
It is true that rainwater has a pH below 7 due to the absorption of CO₂, which forms carbonic acid and makes the rain slightly acidic.
Step-by-step explanation:
The statement that rainwater has a pH below 7 because raindrops absorb CO₂ which can react with water to form carbonic acid is true.
Normal rainwater becomes slightly acidic with a pH between 5 and 6 due to the formation of carbonic acid when CO₂ from the atmosphere dissolves in water. The chemical reaction H₂O(l) + CO₂(g) → H₂CO₃(aq) explains this process.
When discussing acid rain, we refer to rainwater with a pH lower than 5, which occurs when rain contains higher concentrations of acidic compounds such as carbonic acid, sulfuric acid, and nitric acid formed from CO₂, SO₂, SO₃, NO, and NO₂.