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Study the graph… (Class 12 Chemistry SQP 2024-25, Q4)

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ChemistryCBSE Class 12 · Sample paper, session 2024-25 · 1 mark · MCQ

CBSE Class 12 Chemistry sample paper 2024-25: question 4

From the official CBSE sample question paper for 2024-25, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q4 · 1 mark · MCQCompetency-basedHaloalkanes and Haloarenes

Study the graph showing the boiling points of bromoalkanes and identify the compounds.

  1. (A)1 = Bromomethane, 2= 2-Bromobutane, 3= 1-Bromobutane, 4= 2-Bromo-2-methylpropane
  2. (B)1 =1-Bromobutane, 2= 2-Bromo-2-methylpropane, 3= 2-Bromobutane, 4= Bromomethane
  3. (C)1 = Bromomethane, 2=1-Bromobutane, 3= 2-Bromo-2-methylpropane, 4= 2-Bromobutane,
  4. (D)1 =Bromomethane, 2= 2-Bromo-2-methylpropane, 3=2- Bromobutane, 4= 1-Bromobutane

Figure in the paper: Bar chart titled 'Boiling points of bromoalkanes'. X-axis: Bromoalkanes 1, 2, 3, 4; y-axis: Boiling point/K (0 to 400). Bar values: 1 = 277, 2 = 346, 3 = 364, 4 = 375. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

Smaller molecules boil lower.

Hint 2

For isomers, more branching means a lower boiling point.

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. Bromomethane has the smallest molar mass, so it has the lowest b.p. (277 K).

  2. Among the isomeric bromobutanes, b.p. falls as branching increases because surface area and van der Waals forces decrease. So 1-bromobutane (375 K) > 2-bromobutane (364 K) > 2-bromo-2-methylpropane (346 K). Option (D).

    1 mark

Answer: Option (D)

Where the marks are

  • Applies the molar mass and branching trends correctly (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 paperSample paper 2024-25: 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.