Which of the following species can act as the strongest base ? (A) OH^- (B) C_6H_5O^- (C) RO^- (D) 3-nitrophenoxide ion (benzene ring with O^- and O_2N groups meta to each other)

ChemistryCBSE Class 12 · Board exam 2024, set 56/5/1 · 1 mark · MCQ

CBSE Class 12 Chemistry 2024: question 10

Set in the CBSE Class 12 board exam of 2024, paper 56/5/1, section A, question 10, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q10 · 1 mark · MCQAlcohols, Phenols and Ethers

Which of the following species can act as the strongest base ?

(A) $O H^{-}$
(B) $C_{6} H_{5} O^{-}$
(C) $R O^{-}$
(D)3-nitrophenoxide ion (benzene ring with $O^{-}$ and $O_{2} N$ groups meta to each other)

Figure in the paper: Option (D) shows a benzene ring with O^- on one carbon and NO2 (O2N) on the meta position. See it in the official paper.

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

Compare the conjugate acids of the given species.

Hint 2

The weakest acid gives the strongest conjugate base.

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 acid strengths are 3-nitrophenol > phenol > water > alcohol. The weakest acid has the strongest conjugate base.
The alcohol is the weakest acid, so $R O^{-}$ is the strongest base. Its alkyl group (+I effect) also intensifies the negative charge. Option (C).
1 mark

Answer: $R O^{-}$ , option (C)

Where the marks are

Identifies alkoxide as the strongest base (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 10

Hints

Step-by-step solution

Revise the chapter

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