Question

Acid rain corrodes the marble of the monument. The phenomenon is called:
A. Destruction
B. Marble cancer
C. Corrosion
D. Rusting

Answer 1

Hint: To answer this question we should note that acids have a corrosive effect on limestone or marble. Sulphur dioxide, nitrogen dioxide are the constituents that are present in acid rain.

Step by step answer:
We should first know about acid rain. Acid rain is a form of precipitation with acidic components, such as sulphuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic. Here, we should note that acid rain results when sulphur dioxide and nitrogen oxides (\[N{{O}_{x}}\]) are emitted into the atmosphere and transported by wind and air currents. These react with water, oxygen and other chemicals to form sulphuric and nitric acids. These then mix with water and other materials before falling to the ground.
When sulphurous, sulphuric, and nitric acids in polluted air and rain react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive. You might expect that sheltered areas of stone buildings and monuments would not be affected by acid precipitation. However, sheltered areas on limestone and marble buildings and monuments show blackened crusts that have peeled off in some places, revealing crumbling stone beneath. This black crust is primarily composed of gypsum, a mineral that forms from the reaction between calcite, water, and sulphuric acid. Gypsum is soluble in water; although it can form anywhere on carbonate stone surfaces that are exposed to sulphur dioxide, it is usually washed away. It remains only on protected surfaces that are not directly washed by the rain.
So, from the above discussion we can say that marbles get corroded when kept in open for a long time, because of acid rain. We know that marble are made up of calcium carbonate. And when acid present in rain reacts with calcium carbonate, this results in the corrosion. And this is known as Marble cancer. So, option B is correct.

Note: We should know measures to control acid rain. So, power plants should use coal that contains less sulphur. Sulphur is present in coal as an impurity, and it reacts with air when the coal is burned to form sulphur dioxide. Another option is to wash the coal to remove some of the sulphur. Power plants can also install devices called scrubbers to chemically remove the sulphur dioxide from the gases leaving the smokestacks of the power plants. Alternatively, power plants can change their fuels by using natural gas. Burning natural gas creates much less sulphur dioxide than coal.