1998 General Studies, all questions

UPSC Prelims 1998 · General Studies

Question 127: Science and Technology

Assertion (A): Formic acid is a stronger acid than acetic acid. Reason (R): Formic acid is an organic acid.

aBoth A and R are true, and R is the correct explanation of A
bBoth A and R are true, but R is NOT a correct explanation of A
cA is true, but R is false
dA is false, but R is true

AnswerThe answer is (b).

Formic acid (HCOOH) is about ten times stronger than acetic acid (CH3COOH): its Ka is about 1.8 x 10^-4 against 1.8 x 10^-5. The methyl group in acetic acid pushes electrons towards the carboxylate group, making its ion less stable. R is true, since formic acid is an organic acid, but that does not explain the strength, as acetic acid is also organic and is weaker.

  • A. Formic acid is a stronger acid than acetic acid.
  • R. Formic acid is an organic acid, but so is acetic acid, so this does not explain the difference.

How you could have got this

If you were sure statement 1 is correct, (d) goes. Then judge the second statement; if it is correct too, decide whether it explains the first.

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) Being organic does not make formic acid stronger than acetic acid.
  • (b) Right: both are true, but R does not explain A.
  • (c) R is true, so this fails.
  • (d) A is true, so this fails.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 1998, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.