Question

What type of reaction illustrates how acid rain causes the decomposition of marble monuments?

Answer 1

In the above question, it is asked about the reaction which takes places which leads to decomposition of marble monuments. Acid rain leads to discoloration of monuments. It contains sulphuric acid.

Complete step by step solution:
Acid rain can be defined as the rain which contains acid in it or we can refer to it as any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This may include rain, snow, fog, hail or even dust that is acidic.
Acid rain basically results from sulfur dioxide ( ${\text{S}}{{\text{O}}_{\text{2}}}$ ) and nitrogen oxides ( ${\text{N}}{{\text{O}}_{\text{X}}}$ ) which are emitted into the atmosphere. These gases are usually transported by wind and air currents. When these gases react with water, oxygen and other chemicals, it forms sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.
The effect of these acids leads to discoloration of monuments . The marble building consist of calcium carbonate and hence, the reaction between calcium carbonate and sulfuric acid is as:
${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}{\text{ + CaC}}{{\text{O}}_{\text{3}}} \to {\text{SO}}_{\text{4}}^{{\text{2 - }}}{\text{ + C}}{{\text{a}}^{{\text{2 + }}}}{\text{ + C}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$
Here the decomposition of calcium carbonate takes place. Hence, it is an example of decomposition reaction.

Note:
The various factors which leads to acid rain are:
Fossils fuels are burned to generate electricity which results in emission of harmful gases. Two thirds of ${\text{S}}{{\text{O}}_{\text{2}}}$ and one fourth of ${\text{N}}{{\text{O}}_{\text{X}}}$ in the atmosphere come from electric power generators.
The emission of pollutants from vehicles and heavy equipment also contributes to acid rain.