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Two solutions M and N give… (Class 10 Science 2023, Q21b)

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ScienceCBSE Class 10 · Board exam 2023, set 31/5/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 21(b)

Set in the CBSE Class 10 board exam of 2023, paper 31/5/1, section B, question 21(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(b) · 2 marks · Very short answerAcids, Bases and Salts

Two solutions M and N give Red and Blue colour respectively with a universal indicator.

  1. (i)

    In which solution will the hydrogen ion concentration be more ? Justify your answer.

    0 marks
  2. (ii)

    If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed ? Justify your answer.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/5/1.

Hints

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

Hint 1

Recall the universal indicator colour chart: red, green and blue correspond to which pH ranges?

Hint 2

A lower pH means a higher concentration of which ion?

Hint 3

What happens when an acid and a base are mixed in suitable amounts?

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) Solution M has the higher hydrogen ion concentration.

    ½ mark

  2. A red colour with universal indicator means a low pH, so M is acidic and contains more ions. N gives blue, so it is basic and has fewer ions.

    ½ mark

  3. (ii) The salt formed is neutral (green with universal indicator means pH ≈ 7).

    ½ mark

  4. Justification: M is an acid and N is a base. They neutralise each other to form a salt and water, so the mixture is neutral.

    ½ mark

Answer: (i) M, because it is acidic (red, low pH); (ii) the salt is neutral, formed by neutralisation of acid M with base N

Where the marks are

  • Chooses M (½ mark)
  • Justifies: M is acidic, low pH (½ mark)
  • States that the salt is neutral (½ mark)
  • Justifies: acid + base neutralisation (½ 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 paper2023 board paper, set 31/5/1: 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.