Question

The degree of dissociation of acetic acid in its 0.1 M solution is 0.0132 at 25°C. Calculate the degree of dissociation in its 0.01 M solution.

Answer 1

Given: C = 0.1 M, ∝ = 0.0132, C' = 0.01 M, ∝ = 0.0132, ∝' = ?

K_a = ∝²C

C = Molar concentration of acetic acid = 0.1 M

∝ = Degree of dissociation in 0.1 M solution = 0.0132

${\displaystyle \therefore \propto =\sqrt{\frac{K_a}{C}}}$

If the concentration is ${\displaystyle C^{\prime },{\propto }^{\prime }=\sqrt{\frac{K_a}{C^{\prime }}}}$

${\displaystyle \therefore \frac{{\propto }^{\prime }}{\propto }=\sqrt{\frac{C}{C^{\prime }}}=\sqrt{\frac{0.1}{0.01}}=\sqrt{10}}$

${\displaystyle {\propto }^{\prime }=\propto \sqrt{10}=1.32\times {10}^{-2}\sqrt{10}}$

= 4.175 × 10⁻²

∴ degree of dissociation in 0.01 M solution = 4.175 × 10⁻²