Phenol associaes in bensen to a certain extent to from a dimer. A solution containing 2.0xx10^(-2) kg of phenol in 1.0 kg of benzene has a greezing point decreased by 0.69 K. What is the degree of association of phenol ? (K_(f) for benzene=5.12 K kg mol^(-1)).

Phenol associaes in bensen to a certain extent to from a dimer. A solu

1.	Phenol associaes in bensen to a certain extent to from a dimer. A solution containing 2.0xx10^(-2) kg of phenol in 1.0 kg of benzene has a greezing point decreased by 0.69 K. What is the degree of association of phenol ? (K_(f) for benzene=5.12 K kg mol^(-1)).
Answer» Solution :Step I. Calculation of OBSERVED molar mass of phenol `M_(B)=(K_(f)xxW_(B))/(W_(A)xxDeltaT_(f))=((5.12" K kg mol"^(-1))xx(2.0xx10^(-2)kg))/((1.0kg)xx0.69K)` `=14.84xx10^(-2)" kg mol"^(-1)=148.4" G mol"^(-1)` Step II. Calculation of Van't Hoff factor `"Van't Hoff factor (i)"=("Normal molar mass of phenol")/("Obsrved molar mass of phenol")` `=((94" g mol"^(-1)))/((148.4" g mol"^(-1)))=0.633` Step III. `"Calculation of DEGREE of association of phenol "(alpha)` `2C_(6)H_(5)OHhArr(C_(6)H_(5)OH)_(2)` `alpha=(i-1)/(1/n-1)=((0.633-1))/((1/2-1))=((-0.367))/((-0.500))=0.734 or 73.4`%