It is currently the most common material used for metalling roads in place of bitumen.
Explanation
Coal tar is a thick, black liquid with an unpleasant smell, obtained as a byproduct during the destructive distillation of coal to produce coke. It is a complex mixture of about 200 carbon compounds and serves as a vital raw material for various industrial applications.
Statement-wise Analysis:
- Statement It is used as a starting material for manufacturing synthetic dyes and drugs. is Correct: Products obtained from coal tar are extensively used as starting materials for manufacturing synthetic dyes, drugs, explosives, perfumes, plastics, and paints.
- Statement It is used in the manufacture of photographic materials and roofing materials. is Correct: Coal tar derivatives are utilized in the manufacture of photographic materials and roofing materials.
- Statement It is the primary source for obtaining naphthalene balls used to repel moths. is Correct: Naphthalene balls, which are commonly used to repel moths and other insects, are obtained directly from coal tar.
- Statement It is currently the most common material used for metalling roads in place of bitumen. is Incorrect: While coal tar was historically used for metalling roads, it has been largely replaced. Currently, Bitumen, a petroleum product, is the standard material used for metalling roads due to its superior properties and availability.
Key Takeaway:
Bitumen (a petroleum product) has replaced coal tar as the primary material for metalling roads in modern infrastructure.