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Answer the following… (Class 12 Chemistry SQP 2025-26, Q17A)

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ChemistryCBSE Class 12 · Sample paper, session 2025-26 · 2 marks · Very short answer

CBSE Class 12 Chemistry sample paper 2025-26: question 17(A)

From the official CBSE sample question paper for 2025-26, section B, question 17(A), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q17(A) · 2 marks · Very short answerCompetency-basedSolutions

Answer the following:
I. When 50 mL of phenol and 50 mL of aniline are mixed, predict whether the volume of the solution is equal to, greater than or less than 100 mL. Give reason to support your answer.
II. Ritesh suggested adding salt to the box containing ice. He said this would keep the cold drink bottles cold for a longer time. How will Ritesh justify his suggestion?

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

Think about whether phenol–aniline attractions are stronger or weaker than those in the pure liquids.

Hint 2

Stronger A–B attraction means negative deviation, and what does that do to volume?

Hint 3

For II, recall which colligative property a solute changes for ice and water.

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. I. The volume will be less than 100 mL. A phenol–aniline mixture shows negative deviation from Raoult's law. Strong intermolecular hydrogen bonding forms between the –OH of phenol and the –NH of aniline. These attractions are stronger than phenol–phenol and aniline–aniline attractions, so the molecules pack more closely and .

    1 mark

  2. II. Salt dissolves in the water from the melting ice and causes depression in freezing point (). The ice–brine mixture therefore stays in equilibrium at a temperature below 0 °C (a freezing mixture). The bottles stay colder for a longer time.

    1 mark

Answer: I. Less than 100 mL (negative deviation; stronger phenol–aniline H-bonding). II. Salt depresses the freezing point, so the ice–salt mixture stays below 0 °C and keeps the drinks cold longer.

Where the marks are

  • States volume < 100 mL with reason: stronger phenol–aniline H-bonding / negative deviation (1 mark)
  • Explains depression in freezing point by salt keeping the mixture colder/ice lasting longer (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Solutions, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26: 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.