what is the difference between degree of dissociation and degree of association? please add formulas for both...

Asked by yashrajgharte24.12dgatl | 20th Jul, 2021, 02:34: PM

Expert Answer:

Association:
  • Consider an example of association of acetic acid. Molecules of acetic acid dimerise in benzenedue to hydrogen bonding. In this case, the number of particles is reduced due to dimerisation.
 
 
  •  If all the molecules of ethanoic acid associate in benzene, then ΔTb or ΔTf for ethanoic acid will behalf of the normal value.
 
  • The molar mass calculated on the basis of this ΔTb or ΔTf will therefore be twice the expectedvalue.
 
  • Such a molar mass that is either lower or higher than the expected or normal value is calledabnormal molar mass.
 
Dissociation:
 
  • If we dissolve one mole of KCl (74.5 g) in water, we expect one mole each of K+and Cl−ions to bereleased in the solution.
 
              
 
  • If this happens, then there would be two moles of particles in the solution. If we did not know about the degree of dissociation, then we could be led to conclude that themass of 2 mol particles is 74.5 g and the mass of one mole of KCl would be 37.25 g.
 
  •  In the dissociation of the solute into ions, the experimentally determined molar mass is alwayslower than the true value.

Answered by Ramandeep | 20th Jul, 2021, 07:55: PM

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