Question

The molar conductivity of a weak monobasic acid at infinite dilution is 387 ohm⁻¹ cm² mol⁻¹. The 0.02 M solution of the same acid has a specific conductivity of 3.3 × 10⁻⁴ ohm⁻¹ cm² mol⁻¹. Calculate the degree of dissociation of the acid at the given concentration.

Answer 1

Given: κ = 3.3 × 10⁻⁴ Ω⁻¹ cm⁻¹

C = 0.02 mol/L

`Lambda_m^0` = 387 Ω⁻¹ cm² mol⁻¹

Molar conductivity (Λ_m) = `(kappa xx 1000)/C`

= `(3.3 xx 10^-4 xx 1000)/0.02`

= `0.33/0.02`

= 16.5 Ω⁻¹ cm² mol⁻¹

Degree of dissociation (α) = `16.5/387`

= 0.0426 

∴ The degree of dissociation of the acid at the given concentration is 0.0426.