Molar mass of acetic acid determined from colligative property experiments is 80g. Degree of dimerisation of acetic acid is

$i=\frac{\text{ normal molar mass }}{\text{ observed molar mass }}=\frac{60}{80}=0.75$

$nA\to A_n$

1

$1-\beta \frac{\beta }{n}$

$i=\frac{1+\beta \left(\frac{1}{n}-1\right)}{1}=1+\left(\frac{1}{n}-1\right)\beta$

For acetic acid n = 2

$0.75=1+\left(\frac{1}{2}-1\right)\beta ;\beta =0.5$