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Arrange the following… (Class 12 Chemistry 2025, Q6)

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ChemistryCBSE Class 12 · Board exam 2025, set 56/1/1 · 1 mark · MCQ

CBSE Class 12 Chemistry 2025: question 6

Set in the CBSE Class 12 board exam of 2025, paper 56/1/1, section A, question 6, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q6 · 1 mark · MCQHaloalkanes and Haloarenes

Arrange the following compounds in increasing order of their boiling points :
(i) (ii) (iii)
The correct order is

  1. (A)(ii) < (i) < (iii)
  2. (B)(i) < (ii) < (iii)
  3. (C)(iii) < (i) < (ii)
  4. (D)(iii) < (ii) < (i)

Figure in the paper: Structures: (i) isobutyl bromide, two CH3 groups on a CH bonded to CH2Br; (ii) n-butyl bromide CH3CH2CH2CH2Br; (iii) tert-butyl bromide, central C bonded to three CH3 groups (one drawn above) and Br below. See it in the official paper.

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

All three compounds are isomers.

Hint 2

Ask how branching changes surface area and van der Waals forces.

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. For isomers, more branching gives a more compact shape and smaller surface area. This weakens van der Waals forces and lowers the boiling point.

  2. tert-Butyl bromide is the most branched and n-butyl bromide is unbranched, so the order is (iii) < (i) < (ii), option (C).

    1 mark

Answer: (iii) < (i) < (ii), option (C)

Where the marks are

  • Gives the order using the branching argument (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.