UPSC Prelims 2025 GS Paper I · Q5 of 99 General Science medium

Consider the following substances : I. Ethanol II. Nitroglycerine III. Urea Coal gasification technology can be used in the production of how many of them?

  1. (a) Only one
  2. (b) Only two ✓ UPSC's answer
  3. (c) All the three
  4. (d) None

Why the answer is (b)

• Coal gasification reacts coal with steam and oxygen at high temperature to produce syngas — a mixture of carbon monoxide and hydrogen — which is a feedstock for many chemicals.

• Syngas is the route to ammonia (via hydrogen), and ammonia with carbon dioxide gives urea; India's Talcher fertiliser plant is a coal-gasification-to-urea project — III is correct.

• Syngas can also be converted to ethanol, either catalytically or by fermenting it with microbes (as in some 'second-generation' ethanol processes) — I is correct.

• Nitroglycerine is made by nitrating glycerol with a nitric–sulphuric acid mixture; it is not derived from syngas or coal gasification — II is not correct.

• Hence two of the three, option (b).

Why the other options are wrong

(a) Only one
Both ethanol and urea can be produced from gasification-derived syngas.
(c) All the three
Nitroglycerine is made by nitrating glycerol, not from syngas.
(d) None
Urea and ethanol are both syngas-derived products.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2025, held on 25 May 2025. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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