(a) Write two characteristics of non-ideal solution.
(b) 2g of benzoic acid dissolved in 25g of benzene shows a dpression in freezing point equal to -1.62K. Molal depression constant for benzene is 4.9 K kg mol-1. What is the percentage association of acid if it forms dimer in solution?
(a) 1) The enthaply change of mixyure is not zero. The heat is either released or absorbed on mixing solute and solvent.
(-ve or +ve)
2) Change in the volume of solution an addition of solute to solute is not zero, . There is either expansion or contraction.
(b) Weight of solute (W2) = 2g
Kf = 4.9 K kg mol-1
Depression in freezing point =
Weight of solvent (W1) = 25g
Let x be the degree of association.
Undissociated benzoic acid = 1 - x for associated molecule.
Total no. of particles at equilibrium
i =
% association = 0.992 X 100 = 99.2%