AIPMT PRELIMS2009Chemistry-Electrochemistry

AIPMT PRELIMS 2009 Chemistry Conductance and Dissociation MCQ Question

Type: MCQ-numerical-Medium-Class 12

The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mhos cm² and at infinite dilution is 400 mhos cm². The dissociation constant of this acid is:

A

1.25 × 10⁻⁶

B

6.25 × 10⁻⁴

C

1.25 × 10⁻⁴

D

1.25 × 10⁻⁵

Correct Answer

Option D

Detailed Explanation

The degree of dissociation (α) is calculated as Λ/Λ₀ = 8.0/400 = 0.02. The dissociation constant (Kₐ) is given by Kₐ = Cα²/(¹⁻α) ≈ Cα² for weak acids. Substituting C = 1/32 and α = 0.02, we find Kₐ = 1.25 × 10⁻⁵.

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