# in a solvent 50% of benzoic acid dimerises while the rest ionises. determine molar mass of acid which is observed and also its van't hoff factor.

Formula to calculate i ( Van't haff factor) using $\alpha$ (degree of ionizaion) is as follows:
i = (​1-$\alpha$) + $\frac{\alpha }{n}$
Here,
$\alpha$ = 50/100 = 0.5
n ​= 2 (dimerisation)
i = (1.0-0.5) + 0.5/2
= 0.75

i =

0.75 =

Observed Molar mass = 0.75 x 122 g/mol
= 91.5 g/mol

• -35

alpha = 50/100 = 0.5 put in formula i = 1 - 0.5 + 0.5/2 here 2 is the dimerization or dissociation as its dissociated to 2 ions so i = 0.5 + 0.25 = 0.75 now for mass put in the equation i = observed mass/normal mass = 0.75 = x/122 = x = 91.5 so mass is 91.5 grams observed

• -20
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