Question

Statues and monuments in India are affected by acid rain. How?

Answer 1

Hint:Acid rain generally involves any form of precipitation which is acidic comprising of high levels of hydrogen ions. It is mainly composed of acidic components like sulphuric acid or nitric acid which tends to fall to the ground from the atmosphere in either wet or dry forms. These forms mainly include snow, rain, fog, hail, etc.

Complete answer:Acid rain is actually a by-product of numerous human activities which lead to the emission of oxides of carbon, sulphur or nitrogen (i.e. $$C{O}_2,S{O}_2,orN{O}_2$$, respectively) in the atmosphere. All these oxides usually undergo oxidation and correspondingly react with water vapour in order to form acids including carbonic acid, sulphuric acid or nitric acid as indicated in the following reactions:
$$\begin{array}{l}C{O}_2\left(g\right)+H_{2}O\left(l\right)\to H_{2}C{O}_3\left(aq\right)\\ 2S{O}_2\left(g\right)+O_2\left(g\right)+2H_{2}O\left(l\right)\to 2H_{2}S{O}_4\left(aq\right)\\ 4N{O}_2\left(g\right)+O_2\left(g\right)+2H_{2}O\left(l\right)\to 4HN{O}_3\left(aq\right)\end{array}$$
​These produced acid results into the acid rain which causes damage (or we can say corrodes) to the buildings and the structures made out of stone or metal. In India, we know that limestone is majorly used as a stone in the construction of most of the monuments and statues, for instance, the Taj Mahal. Calcium carbonate present in the monuments reacts with the acid of the acid rain according to the following reaction:
$$CaC{O}_3+H_{2}S{O}_4\to CaS{O}_4+H_{2}O+C{O}_2$$
This results in the loss of colour and lustre of the monuments, leading to the blackening of the marble surfaces.

Note:When acid rain falls to the earth, nitric, carbonic and sulphuric acid which make the particles acidic may land on buildings, statues, and manmade structures, and can cause damage to their surfaces. As a result, acidic particles can corrode metal and can cause paint as well as stone to deteriorate.