Question

Answer the following in one sentence :

The dissociation constant of acetic acid is 1.8 × 10^-5. Calculate percent dissociation of acetic acid in 0.01 M solution.

Answer 1

Given :

• Dissociation constant (K_a) = `1.8 xx 10^-5`,
• Concentration (c) = 0.01 M

To find :

• Percent dissociation

Formulae : 

1. K_a = α²c
2. Percent dissociation = α × 100

Calculation :

c = 0.01, M = `1 xx 10^-2 "M"`

Using formula (i),

∴ α = `sqrt(("K"_"a")/("c"))`

= `sqrt((1.8 xx 10^-5)/(1 xx 10^-2)) = sqrt(1.8 xx 10^-3) = sqrt(18 xx 10^-4)`

= `4.242 xx 10^-2`

Using formula (ii),

Percent dissociation = `α × 100 = 4.242 xx 10^-2 xx 100 = 4.242%`

Percent dissociation of 0.01 M acetic acid solution is 4.242%.