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pure benzene freezes at 5.3^(@)C. A solu...

pure benzene freezes at `5.3^(@)C`. A solution of 0.233 g of phenyl acetic acid `(C_(6)H_(5)CH_(2)COOH)` freezes at `4.47^(@)C`. Form this observation, one can conclude that pbenyl acetic acid

A

exists as such in benzene

B

undergoes partial ionisation in benzene.

C

undergoes complete ionisation in benzene

D

dimerises in benzene.

Text Solution

Verified by Experts

The correct Answer is:
d
`DeltaT_(f)=5.3-4.47=0.83 K`
`"Molaliy (m)"=((0.223 g)//(0.0044 kg))/((136 g mol^(-1)))`
`=0.373 mol//kg`
`DeltaT_(f)=iK_(f)m`
`i=(DeltaT_(f))/(K_(f)m)=((0.83K))/((5.12 K mol^(-1))xx(0.373 mol kg^(-1)))`
=0.435.
Since I is close to 0.5, this means that the acid dimerises in benzene.
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