WBJEE 2024 Physics & Chemistry Paper

To find the degree of dissociation of the acetic acid, we first need to calculate the molar conductivity (Λm) of the solution. The formula for molar conductivity is:
Λm=‌

κ

c

where:
κ (kappa) is the specific conductance.
c is the concentration of the acetic acid solution.
Given:
‌κ=1.65×10−4Scm−1
‌c=0.02M
Substituting these values into the formula for molar conductivity:
Λm=‌

1.65×10−4

0.02

Calculating this gives:
Λm=8.25×10−3Scm2mol−1
Next, we need to find the limiting molar conductivity (Λm0) of acetic acid, which is the sum of the limiting molar conductivities of its ions:

Λm0=λO+∘+λCH3‌COO0
Given:
‌λO++∘=349.1Scm2mol−1
‌λCH3COO−∘=40.9Scm2mol−1

Calculating the limiting molar conductivity:
Λm0=349.1+40.9=390Scm2mol−1

The degree of dissociation (α) can now be determined using the ratio of the molar conductivity to the limiting molar conductivity:
α=‌

Λm

Λm0

Substituting the values we calculated:

α=‌

8.25×10−3

390

Calculating this gives:
α=2.115×10−5≈0.021
The degree of dissociation of the acetic acid is approximately 0.021 . Hence, the correct option is:
Option A