`1.22 g` of benzoic acid is dissolved in (i) 100g acetone `(K_(b)` for acetone `=1.7)` and (ii) 100 g benzene `(K_(b)` for benzene `= 2.6)`. The eleva
`1.22 g` of benzoic acid is dissolved in (i) 100g acetone `(K_(b)` for acetone `=1.7)` and (ii) 100 g benzene `(K_(b)` for benzene `= 2.6)`. The elevation in boiling points `T_(b)` is `0.17^(@)C` and `0.13^(@)C` respectively.
(a) What are the molecular weights of benzoic acid in both the solutions?
(b) What do you deduce out of it in terms of structure of benzoic acid?
1 Answers
Correct Answer - (a)122,
(b) It means that benzonic acid remains as it is in acetone while it dimerises in benzene
`DeltaT_(b)=ixxK_(b)xx(W_("solute")xx1000)/(m_("solute")xxW_("solvent"))`
For solution of benzonic acid in acetone
`0.17=ixx1.7xx(1.22xx1000)/(122xx100)`
`i=1`
`therefore` benzonic acid does not dimerise in acetone
Now, for solution of benzonic acid in bezonic
`0.13=ixx2.6(1.22xx1000)/(122xx100)`
`i=1/2`
`i=1+((1)/(2)-1)alpha`
If we assume `alpha=100%`
`n=2`
`therefore` Benzonic acid dimerise in benzene.