ScienceCBSE Class 10 · Board exam 2023, set 31/6/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 4

Set in the CBSE Class 10 board exam of 2023, paper 31/6/1, 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

Two salts 'X' and 'Y' are dissolved in water separately. When phenolphthalein is added to these two solutions, the solution 'X' turns pink and the solution 'Y' does not show any change in colour, therefore 'X' and 'Y' are

	(X)	(Y)
(a)	$N a_{2} C O_{3}$	$N H_{4} Cl$
(b)	$N a_{2} S O_{4}$	$NaHC O_{3}$
(c)	$N H_{4} Cl$	$N a_{2} S O_{4}$
(d)	$NaN O_{3}$	$N a_{2} S O_{4}$

(A)X: Na2CO3, Y: NH4Cl
(B)X: Na2SO4, Y: NaHCO3
(C)X: NH4Cl, Y: Na2SO4
(D)X: NaNO3, Y: Na2SO4

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/6/1.

Hints

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

Hint 1

In what kind of solution does phenolphthalein turn pink?

Hint 2

Work out whether each salt gives an acidic, basic or neutral solution.

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.

Phenolphthalein turns pink only in a basic solution. $N a_{2} C O_{3}$ is a salt of a strong base and a weak acid, so its solution is basic. This makes it X.
½ mark
$N H_{4} C l$ gives an acidic solution, so phenolphthalein stays colourless. This makes it Y. Hence the answer is option (A).
½ mark

Answer: X = Na2CO3, Y = NH4Cl, option (A)

Where the marks are

Recognises X is basic (Na2CO3) and Y is acidic (NH4Cl) (1 mark)

Revise the chapter

Chapter: Acids, Bases and Salts (notes, formulas, where marks are lost and every past question)

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 31/6/1: every question, by section.

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CBSE Class 10 Science 2023: question 4

Hints

Step-by-step solution

Revise the chapter

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