1.

The freezing point of benzene decreases by 0.45^(@)C when 0.2 g of acetic acid is added to 20 g of benzene. IF acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be (K_(f) "for benzene" = 5.12 K kg mol^(-1))

Answer»

0.746
0.946
0.646
0.804

Solution :`"MOLALITY (m)"=("No.of moles of "CH_(3)COOH)/("MASS of benzene in kg")`
`((0.2))/((60 g MOL^(-1))xx(0.02kg))`
`=0.167 mol kg^(-1)=0.167m`
`DeltaT_(f)=ixxK_(f)xxm or i=(DeltaT_(f))/(K_(f)xxm)`
`i=((0.45K))/((5.12 "K kg mol"^(-1))xx(0.167"mol kg "^(-1)))=0.526`
`alpha=((i-1))/((n-1))=((0-526-1))/((0.5-1))`
`=((-0474))/((-0.5))=0.948 %`


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