Phenol associates in benzene to a certain extent to form dimer. A solution containing 2.0xx10^(-2)kg of phenol in 1.0 kg of benzene has its freezing point decreased by 0.69 K. Calculate the degree of association of phenol (K_(f)" for benzene = 5.12 K kg mol"^(-1)).

Phenol associates in benzene to a certain extent to form dimer. A solu

1.	Phenol associates in benzene to a certain extent to form dimer. A solution containing 2.0xx10^(-2)kg of phenol in 1.0 kg of benzene has its freezing point decreased by 0.69 K. Calculate the degree of association of phenol (K_(f)" for benzene = 5.12 K kg mol"^(-1)).
Answer» Solution :`M_(2)"(observed)"=(1000K_(f)w_(2))/(w_(1)DeltaT_(f))=("1000 g kg"^(-1)xx"5.12 K kg mol"^(-1)xx2.0xx10^(-2)kg)/(1.0kg xx0.69K)="148.4 g mol"^(-1)` `M_(2)"(calculated) for "C_(6)H_(5)OH="94 g mol"^(-1)""therefore""i=(M_(2)"(calculated)")/(M_(2)"(observed)")=(94)/(148.4)=0.633` `{:(,2C_(6)H_(5)OHhArr(C_(6)H_(5)OH)_(2)),("Initial","1mol"),("After asso."," "1-alpha""alpha//2"Total "=1-alpha//2):}` `i=(1-alpha//2)/(1)"or"alpha=2(1-i)=2(1-0.633)=0.734.`