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Assertion (A) : The boiling… (Class 12 Chemistry 2025, Q14)

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ChemistryCBSE Class 12 · Board exam 2025, set 56/1/1 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry 2025: question 14

Set in the CBSE Class 12 board exam of 2025, paper 56/1/1, section A, question 14, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q14 · 1 mark · Assertion-reasonCompetency-basedHaloalkanes and Haloarenes

Assertion (A) : The boiling points of alkyl halides decrease in the order : RI > RBr > RCl > RF.
Reason (R) : The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.

  1. (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  2. (B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (D)Assertion (A) is false, but Reason (R) is true.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 56/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Check each statement on its own first.

Hint 2

Ask whether R compares halides with each other or with hydrocarbons.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Boiling point rises with the size and mass of the halogen, so RI > RBr > RCl > RF. A is true.

  2. R is also true, because the polarity of the C–X bond and the higher molar mass increase intermolecular forces. R does not explain the trend among the halides, so the answer is option (B).

    1 mark

Answer: Option (B)

Where the marks are

  • Recognises both statements are true but R does not explain A (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Haloalkanes and Haloarenes, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 56/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.