(1) sulfur dioxide combined with water to generate sulfurous acid, oxidized by oxygen in the air to sulfuric acid, and finally generate hydrochloric acid, sulfuric acid and hydrochloric acid are corrosive, so this process requires corrosion-resistant equipment; sulfur dioxide is the main component in the formation of acid rain, the process absorbs sulfur dioxide, so the use of this exhaust gas treatment device can reduce the formation of acid rain;
(2) the reactants are sulfur dioxide, Oxygen, water, sodium chloride written on the left side of the equals sign, the product is sodium sulfate and hydrochloric acid written on the right side of the equals sign, using the observation method of leveling can be, so the total equation is:
2SO2+O2+2H2O+4NaCl ═2Na2SO4+4HCl.
Therefore, the answer is: (1) AB; (2) 2SO2+O2+2H2O+4NaCl ═ 2Na2SO4+4HCl.