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Acetic acid associates in benzene to for...

Acetic acid associates in benzene to form a dimer. `1.65 g` of acetic acid when dissolved in `100 g` of benzene raised the boiling point by `0.36^(@)C`. Calculate the Van't Hoff factor and degree of association of acetic acid.
(`K_(b)` for benzene=`2.57^(@)C`)

Text Solution

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Calculation of Van't Hoff factor:
First calculate the molecular mass form elevation in boiling point.
`Mx_(B)=K_(b)(W_(B)/(W_(A)DeltaT_(b))xx1000)`
`=2.57(1.65/(100xx0.36)xx1000)=117.8`
`rArr I = "Normal molecular weight"/"Observed molecular weight" =60/117.8 =0.509`
Calculation of degree of association:
Let `x`=degree of association:

Total moles=`1-x//2`
`i="Total moles"/"Initial moles" =(1-x//2)/1`
`rArr 0.509=(1-x//2)/1 rArr x=0.982`
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