1. Acids rains are rains which have acidic components such as sulfuric acid, nitric acid and carbonic acid. Those acids are made by dissolving the components in water which are from oxidation of the gases such as SO₂, NO₂ and CO₂. The marble has CaCO₃ as the major component. The acids in acid rains can react with CaCO₃ by producing soluble salts. That's why acid rain dissolves statues made of marble.
2. The reaction between CaCO₃ and H₂SO₄ acid is
CaCO₃(s) + H₂SO₄(aq) → CaSO₄(aq) + CO₂(g) + H₂O(l)
CaSO₄ is slightly soluble in water. But the solubility of CaSO₄ compared to CaCO₃ is very high. Hence, due to the acid rains, degradation of statues made of marble (CaCO₃) is higher than in normal situations.
