_m^o CH_3COOH can be calculated if the values of the following are given: 1. _m^oHCl, _m^oKCl and _m^o CH_3COOK 2. _m^oNaCl, _m^oKCl and _m^o CH_3COONa 3. _m^oH_2SO_4, _m^oNa_2SO_4 and _m^o CH_3COONa (A) Only 1 (B) Either 1 or 2 (C) Either 1 or 3 (D) Either 2 or 3

ChemistryCBSE Class 12 · Sample paper, session 2025-26 · 1 mark · MCQ

CBSE Class 12 Chemistry sample paper 2025-26: question 10

From the official CBSE sample question paper for 2025-26, section A, question 10, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q10 · 1 mark · MCQElectrochemistry

$Λ_{m}^{o}$ $C H_{3} COOH$ can be calculated if the values of the following are given:
1. $Λ_{m}^{o}$ HCl, $Λ_{m}^{o}$ KCl and $Λ_{m}^{o}$ $C H_{3} COOK$
2. $Λ_{m}^{o}$ NaCl, $Λ_{m}^{o}$ KCl and $Λ_{m}^{o}$ $C H_{3} COONa$
3. $Λ_{m}^{o} H_{2} S O_{4}$ , $Λ_{m}^{o} N a_{2} S O_{4}$ and $Λ_{m}^{o}$ $C H_{3} COONa$

(A)Only 1
(B)Either 1 or 2
(C)Either 1 or 3
(D)Either 2 or 3

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

You need $λ^{o}$ of both H⁺ and CH₃COO⁻.

Hint 2

Check which sets contain a strong acid.

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.

By Kohlrausch's law, set 1 gives $Λ_{C H_{3} C O O H}^{o} = Λ_{H C l}^{o} + Λ_{C H_{3} C O O K}^{o} - Λ_{K C l}^{o}$ .
Set 3 gives $Λ_{C H_{3} C O O H}^{o} = \frac{1}{2} Λ_{H_{2} S O_{4}}^{o} + Λ_{C H_{3} C O O N a}^{o} - \frac{1}{2} Λ_{N a_{2} S O_{4}}^{o}$ . Set 2 contains no $H^{+}$ source, so it cannot be used.
1 mark

Answer: Either 1 or 3, option (C)

Where the marks are

Applies Kohlrausch law to sets 1 and 3 (1 mark)

Revise the chapter

Chapter: Electrochemistry (notes, formulas, where marks are lost and every past question)
Topic: Conductivity, Molar Conductivity and Kohlrausch's Law

Practise this chapterBoard-style questions from Electrochemistry, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26: every question, by section.

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.

CBSE Class 12 Chemistry sample paper 2025-26: question 10

Hints

Step-by-step solution

Revise the chapter

More questions from Electrochemistry