Nitric acid in acid rain forms when gaseous nitrogen dioxide pollutant reacts with gaseous oxygen and liquid water to form aqueous nitric acid. Write a balanced chemical equation for this reaction. Express your answer as a chemical equation. Identify all of the phases in your answer.

For this reaction, the reactants are nitrogen dioxide, oxygen and water while the product would be nitric acid. The chemical equation would be written as:

NO2 (g) + O2 (g) + H2O (l) - - > HNO3 (aq)

This can be a complete equation when the elements are balanced in each side.

4NO2 (g) + O2 (g) + 2 H2O (l) - - > 4HNO3 (aq)