Sat February 23, 2013 By: Shashank Mishra

sir please explain me in very keen manner that what is asoociation and dissociaton and provide me knowledge dip to tackle the problem relatin g asoociation and dissociation ?

Expert Reply
Sat February 23, 2013
Many organic solutes when dissolved in non-aqueous (non polar) solvent associate to form a bigger molecule. Thus the no. of molecules decreases and hence colligative properties decrease.
Acetic acid in benzene, chloro acetic acid in naphthalene

Association of two molecules (dimerisation) of acetic acid in benzene.
 Some solutes (organic acids, bases and salts) in aqueous solution undergo dissociation. In such case no. of particles increases and hence colligative properties increase.
Dissociation of NaCl in aqueous solution.
Consider the following dissociation reaction,
(1 - ?)
Na+(aq) +
Cl- (aq)

moles after dissociation

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