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JEE Main 2025 Apr 3 Shift 2, Chemistry Q1: Conductance Of Electrolytic Solutions

JEE Main2025Apr 3, Shift 2Chemistry
Q.

40 mL of a mixture of CHCOOH and HCl (aqueous solution) is titrated against 0.1 M NaOH solution conductometrically. Which of the following statement is correct?

  1. A

    The concentration of CHCOOH in the original mixture is 0.005 M

  2. B

    The concentration of HCl in the original mixture is 0.005 M

  3. C

    CHCOOH is neutralised first followed by neutralisation of HCl

  4. D

    Point 'C' indicates the complete neutralisation HCl

Solution

In a conductometric titration of a strong acid (HCl) mixed with a weak acid (CHCOOH) against NaOH, the strong acid is consumed first because of its higher H activity. The first sharp drop (A B) corresponds to HCl neutralisation, ending at 2.0 mL. The gentler rise (B C) corresponds to CHCOOH neutralisation, ending at 5.0 mL.

Volume of NaOH used for HCl = 2.0 mL.

Applying at the HCl endpoint:

M.

The HCl concentration in the original mixture is 0.005 M, so option (2) is correct. The acetic acid concentration works out to M, not 0.005 M. Point C marks the end of acetic acid neutralisation, not HCl, and the HCl is the one neutralised first.

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