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(i) In the given… (Class 10 Science SQP 2024-25, Q28A)

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ScienceCBSE Class 10 · Sample paper, session 2024-25 · 3 marks · Short answer

CBSE Class 10 Science sample paper 2024-25: question 28(A)

From the official CBSE sample question paper for 2024-25, section C, question 28(A), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28(A) · 3 marks · Short answerAcids, Bases and Salts

(i) In the given series of reactions, name the compounds X and Z.
(ii) Which type of reaction is X to Z?
(iii) You are given 3 unknown solutions A, B, and C with pH values of 6, 8 and 9.5 respectively. In which solution will the maximum number of hydronium ions be present? Arrange the given samples in the increasing order of ion concentration.

Figure in the paper: Reaction scheme: NaCl + H2O + CO2 + NH3 → X + Y; X on heating (Δ) → Z + H2O + CO2; Z with 10H2O → Q. 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

The first reaction is the industrial preparation of baking soda.

Hint 2

What does baking soda form when heated? Its hydrate with 10H₂O is washing soda.

Hint 3

Lower pH means more H⁺ ions.

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) In the Solvay process, . So **X = sodium hydrogencarbonate, ** (baking soda).

    ½ mark

  2. On heating, , so **Z = sodium carbonate, **. Its decahydrate Q is washing soda.

    ½ mark

  3. (ii) One compound breaks into simpler substances on heating, so X → Z is a (thermal) decomposition reaction.

    ½ mark

  4. (iii) The lower the pH, the higher the concentration. Solution A (pH 6) has the maximum number of hydronium ions.

    ½ mark

  5. Increasing order of concentration: C (pH 9.5) < B (pH 8) < A (pH 6)

    1 mark

Answer: (i) X = NaHCO₃, Z = Na₂CO₃; (ii) thermal decomposition; (iii) A has the most H₃O⁺; C < B < A

Where the marks are

  • X = NaHCO₃ (0.5 mark)
  • Z = Na₂CO₃ (0.5 mark)
  • Decomposition reaction (0.5 mark)
  • Solution A has the maximum hydronium ions (0.5 mark)
  • Order C < B < A (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Acids, Bases and Salts, 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.