2025 GS Paper I, all questions

UPSC Prelims 2025 · GS Paper I

Question 45: Science and Technology

Consider the following substances :

  1. IEthanol
  2. IINitroglycerine
  3. IIIUrea

Coal gasification technology can be used in the production of how many of them?

aOnly one
bOnly two
cAll the three
dNone

AnswerThe answer is (b).

Coal gasification converts coal into syngas, a mixture of carbon monoxide and hydrogen, which is a feedstock for chemicals. Syngas can be turned into ammonia, and ammonia with carbon dioxide yields urea, so urea can come from it. Syngas can also be converted into methanol and other fuels, including ethanol. Nitroglycerine is made by nitrating glycerol with nitric and sulphuric acids and does not come from syngas. So two substances can be produced.

  • I. Ethanol can be produced from syngas.
  • II. Nitroglycerine is made by nitrating glycerol, not from syngas.
  • III. Syngas gives ammonia, which is used to make urea.

How you could have got this

No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Wrong: both ethanol and urea can be made from coal-based syngas.
  • (b) Right: ethanol and urea can be produced from syngas; nitroglycerine cannot.
  • (c) Wrong: nitroglycerine comes from nitrating glycerol, not syngas.
  • (d) Wrong: syngas can be used to make ethanol and urea.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2025, General Studies Paper I, Series A. The paper on upsc.gov.in.