CBSE Class 10 Science 2023: question 4
Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q4 · 1 mark · MCQCompetency-basedAcids, Bases and Salts
The table below has information regarding pH and the nature (acidic/basic) of four different solutions. Which one of the options in the table is correct ?
| Option | Solution | Colour of pH paper | Approximate pH value | Nature of solution |
|---|---|---|---|---|
| (a) | Lemon juice | Orange | 3 | Basic |
| (b) | Milk of magnesia | Blue | 10 | Basic |
| (c) | Gastric juice | Red | 6 | Acidic |
| (d) | Pure water | Yellow | 7 | Neutral |
- (A)(a)
- (B)(b)
- (C)(c)
- (D)(d)
Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/1/1.
Hints
Open one hint at a time and try again before the next.
Hint 1
Recall the universal indicator colours: red/orange for acids, green for neutral, blue/violet for bases.
Hint 2
Check the colour, the pH and the nature in every row. All three must match.
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.
Check each row:
- (a) Lemon juice (pH about 2–3) is acidic, not basic.
- (c) Gastric juice has pH about 1–2, not 6.
- (d) Pure water (pH 7) turns universal indicator green, not yellow.
- 1 mark
Milk of magnesia has pH about 10. It is basic and gives a blue colour on pH paper. So row (b) is correct.
Answer: Option (B)
Where the marks are
- Selects milk of magnesia row, option (B) (1 mark)
Revise the chapter
- Chapter: Acids, Bases and Salts (notes, formulas, where marks are lost and every past question)
- Topic: pH Scale and Its Importance
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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.