Assertion (A) : p-methoxyphenol is a stronger acid than p-nitrophenol. Reason (R) : Methoxy group shows +I effect whereas nitro group shows –I effect. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.

ChemistryCBSE Class 12 · Board exam 2024, set 56/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry 2024: question 16

Set in the CBSE Class 12 board exam of 2024, paper 56/5/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · Assertion-reasonCompetency-basedAlcohols, Phenols and Ethers

Assertion (A) : p-methoxyphenol is a stronger acid than p-nitrophenol.
Reason (R) : Methoxy group shows +I effect whereas nitro group shows –I effect.

(A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(C)Assertion (A) is true, but Reason (R) is false.
(D)Assertion (A) is false, but Reason (R) is true.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 56/5/1.

Hints

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

Hint 1

Electron-withdrawing groups increase the acidity of phenols.

Hint 2

Compare how stable the two phenoxide ions are.

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.

The electron-withdrawing $N O_{2}$ group stabilises the phenoxide ion, while the electron-donating $O C H_{3}$ group destabilises it. So p-nitrophenol is the stronger acid and the Assertion is false.
The Reason is taken as true (methoxy donating, nitro withdrawing). Option (D).
1 mark

Answer: Option (D)

Where the marks are

Assertion false, Reason true (1 mark)

Revise the chapter

Chapter: Alcohols, Phenols and Ethers (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Alcohols, Phenols and Ethers, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 56/5/1: every question, by section.

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CBSE Class 12 Chemistry 2024: question 16

Hints

Step-by-step solution

Revise the chapter

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