Limestone buildings are damaged by acid rain because the acid in the rain reacts with the calcium carbonate in the limestone, causing it to dissolve. The chemical equation for this reaction is:

CaCO3(s) + H2SO4(aq) -> CaSO4(aq) + H2O(l) + CO2(g)

The calcium sulfate that is produced by this reaction is soluble in water, so it is easily washed away by the rain. This leaves the limestone building with a pitted and eroded surface.

In addition to dissolving the calcium carbonate in limestone, acid rain can also cause the metal reinforcement bars in reinforced concrete buildings to corrode. This can lead to the concrete cracking and spalling, which can eventually cause the building to collapse.

Acid rain is a serious problem that is causing damage to buildings and other structures around the world. It is important to take steps to reduce the amount of acid rain that is produced in order to protect our built environment.