vi. Acetic acid is 5% ionised in its decimolar solution. Calculate the dissociation constant of acid

Given: Percent dissociation = 5%, Concentration (c) = 1 decimolar

To find: Dissociation constant of acid (\(K_a\))

Formulae:

i. Percent dissociation = \(\alpha \times 100\)

ii. \(K_a = \alpha^2c\)

Calculation:

Using formula (i),

\(\alpha = \frac{{\text{Percent dissociation}}}{{100}} = \frac{5}{100} = 0.05\)

c = 1 decimolar = 0.1 M

Using formula (ii),

\(K_a = (0.05)^2 \times 0.1\)

= \(2.5 \times 10^{-4}\)

The dissociation constant of the acid is \(2.5 \times 10^{-4}\).