Question

Etching of marble, limestone, jewellery, etc., is caused by pollutant
(a) ${C}{O}_{2}$
(b) ${C}{O}$
(c) ${S}{O}_{2}$
(d) ${C}{H}_{4}$

Answer 1

Hint: The pollutant responsible for the etching of marble, limestone, jewellery, etc., is a toxic gas. It is the gas responsible for the smell of burnt matchsticks. This gas is also released by the activity of volcanoes and also from the burning of fossil fuels.

Complete Step by Step Answer:
The pollutant that etches marble, limestone, jewellery, etc., is Sulphur dioxide or ${S}{O}_{2}$. It is released naturally due to volcanic activity and as a by- product of burning of fossil fuels and also due to copper extraction. Certain acidic compounds such as sulphuric acid and nitric acid are formed from the sulphur and nitrogen present in nature. The sulphur dioxide that is present in nature is the compound that is generally responsible for this. The Sulphuric acid that is formed is highly corrosive and thus it causes etching of marble, limestone, etc.
Sulphur dioxide is one of the main gases that is responsible for acid rain.
So, the correct answer is, “${S}{O}_{2}$”.

Additional Information:
- Acid rain is the phenomenon of precipitation that is unusually acidic due to the presence of acids such as sulphuric acid and nitric acid. It has harmful effects on aquatic life, plants and some aspects of other ecosystems as well.
- Acid rain occurs when oxides of sulphur and nitrogen react with the water molecules in the atmosphere to produce acids which are precipitated along with the rain. Acid rain can cause adverse impact on forests, freshwater, plant growth due to contaminated soils and can even cause paint to peel and corrosion of steel structures.

Note:
- Despite the adverse effects of ${S}{O}_{2}$ due to acid rain, it is still used in many aspects.
- It is easily condensed and has a high heat of evaporation. Due to these properties they are used as refrigerants.
- ${S}{O}_{2}$ is released from fossil fuels which contributes in the etching only when the fossil fuels are contaminated with sulphur compounds. It may not be the case in pure fossil fuels.