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An aqueous solution 'A'… (Class 10 Science SQP 2024-25, Q4)

questionbuddy.in/q/cbse-10-science-2024-25-sqp-q4-aqueous-solution-turns-phenolphthalein-solution

ScienceCBSE Class 10 · Sample paper, session 2024-25 · 1 mark · MCQ

CBSE Class 10 Science 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 · MCQAcids, Bases and Salts

An aqueous solution 'A' turns the phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. Which of the following statement is true for the solutions 'A' and 'B'.

  1. (A)A is strongly basic and B is a weak base.
  2. (B)A is strongly acidic and B is a weak acid.
  3. (C)A has a pH greater than 7 and B has a pH less than 7.
  4. (D)A has a pH less than 7 and B has a pH greater than 7.

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

In which kind of solution does phenolphthalein turn pink?

Hint 2

What must B be in order to remove the base's effect?

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. Phenolphthalein turns pink only in a basic solution, so A is basic and its pH is greater than 7.

    ½ mark

  2. The pink colour disappears when B is added, so B has neutralised the base. B must be an acid, with pH less than 7. The answer is option (C).

    ½ mark

Answer: A has pH > 7 and B has pH < 7; option (C)

Where the marks are

  • Identifies A as basic and B as acidic (neutralisation), giving option (C) (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.