UPSC Prelims 2003 · General Studies

Question 29: Science and Technology

Which one of the following statements is correct?

aLiquid sodium is employed as a coolant in nuclear reactors

bCalcium carbonate is an ingredient of toothpaste

cBordeaux mixture consists of sodium sulphate and lime

dZinc amalgams are used as a dental filling

AnswerThe answer is (a).

Liquid sodium is used as a coolant in fast breeder reactors because it conducts heat very well, has a high boiling point at ordinary pressure and does not slow neutrons much; India's Fast Breeder Test Reactor at Kalpakkam uses it. Bordeaux mixture, a fungicide, is copper sulphate and lime, not sodium sulphate and lime. The usual dental filling is a silver-based amalgam.

Why each option is right or wrong

(a) Correct: liquid sodium is the coolant in fast breeder reactors.
(b) Calcium carbonate is a common toothpaste abrasive, so this is also true in practice.
(c) Bordeaux mixture is copper sulphate and lime, not sodium sulphate and lime.
(d) The standard dental amalgam is silver-based, not zinc.

Worth knowing: Option (b) is also true in practice, since calcium carbonate is a common toothpaste abrasive, so the question has two defensible options.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.