CBSE Class 10 Science sample paper 2025-26: question 20
From the official CBSE sample question paper for 2025-26, section B, question 20, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q20 · 1 mark · MCQAcids, Bases and Salts
Methyl orange is added to dilute hydrochloric acid and to aqueous sodium hydroxide. What is the colour of the methyl orange in each solution?
| Sample | colour in dilute hydrochloric acid | colour in aqueous sodium hydroxide |
|---|---|---|
| A | Orange | Red |
| B | Red | Yellow |
| C | Red | Orange |
| D | Yellow | Red |
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
Methyl orange shows one colour in acids and a different colour in bases.
Hint 2
In an acid it shows a 'warning' colour, and in a base it shows a lighter colour.
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.
Methyl orange is an acid–base indicator. It is red in acidic solutions and yellow in basic solutions.
Dilute HCl is acidic, so methyl orange turns red. Aqueous NaOH is basic, so methyl orange turns yellow.
- 1 mark
The row Red / Yellow is option (B).
Answer: Red in HCl, yellow in NaOH; option (B)
Where the marks are
- Chooses option (B): red in acid, yellow in base (1 mark)
Revise the chapter
- Chapter: Acids, Bases and Salts (notes, formulas, where marks are lost and every past question)
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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.