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Answer the following… (Class 12 Chemistry SQP 2025-26, Q17B)

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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(B)

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

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

Answer the following:
I. on reaction with in aqueous solution gives white precipitate. If the two solutions are separated by a semi-permeable membrane, will there be appearance of a white precipitate due to osmosis?
II. Why does water stops boiling when sugar is added to boiling water.

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

Which particles can pass through a semi-permeable membrane?

Hint 2

For II, compare the vapour pressure of the sugar solution with atmospheric pressure at 100 °C.

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. No, no white precipitate of BaSO will appear. A semi-permeable membrane lets only solvent (water) molecules pass during osmosis. The solute ions Ba and SO cannot cross the membrane, so they never meet.

    1 mark

  2. II. Sugar is a non-volatile solute, so it lowers the vapour pressure of water. The vapour pressure of the solution at 100 °C falls below atmospheric pressure, so boiling stops. The boiling point is elevated (), and the solution boils again only on further heating.

    1 mark

Answer: I. No; only solvent passes through the SPM, so Ba²⁺ and SO₄²⁻ never meet. II. Sugar lowers the vapour pressure, so the boiling point rises and boiling stops until the solution is heated further.

Where the marks are

  • No precipitate, since only solvent molecules move through the SPM in osmosis (1 mark)
  • Non-volatile solute lowers vapour pressure, causing elevation in boiling point (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.