3.9 g of benzoic acid dissolved in 49 g of benzne shows a depreesion in freezing point of `1.62 K`. Calculate the van't Haff factor and predict the nature of solutei (associated or dissociated ). [Given : Molar mass of benzoic acid `= 122 g mol^(-1), K_(f)` for benzene = 4.9 K kg ` mol^(-1)`].

Explanation

`Delta T_(F) = ik_(f) xx m`
` = (ixxk_(f) xx w_(B) xx 100)/(M_(B) xx w_(A))`
` 1.62 = (ixx4.9 xx 3.9 xx 1000)/(122xx49)`
` or " " i= (1.62 xx122xx49)/(4.9 xx 3.9 xx 1000) = 0.506`
Since .i. is less than one the solute is associated .