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What is the resason for reverse basicity of basic buffer solution?I have read that...

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kumarvaibhav123 | Student, Grade 11 | (Level 1) Salutatorian

Posted January 19, 2013 at 4:19 AM via web

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What is the resason for reverse basicity of basic buffer solution?

I have read that reverse basicity of basic buffer solution due to the presence of  undissociated base molecules which gets dissociated to restore the original concentrations of OH- ions but what is the reason for the dissociation the these molecules to restore the concentration of hydroxyl ions.

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llltkl | College Teacher | (Level 3) Valedictorian

Posted January 20, 2013 at 8:20 AM (Answer #1)

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A weak electrolyte is an electrolyte that does not completely dissociate in solution. The solution will contain both dissociated ions and undissociated molecules of the electrolyte. The relative amount of these two types of species in solution is guided by an equilibrium, which is again governed by equilibrium constant, K. K is a function of the nature of the material, solvent and the experimental temperature. It is a constant for a particular electrolyte-solvent pair, and any given temperature.

A basic buffer is composed of a weak base (a weak electrolyte) and its salt with a strong acid (a strong electrolyte). The equilibrium that operates is: BOH = B+ + OH- (Kb = [B+] [OH-]/[ BOH]). When a small quantity of acid is added to it, the free OH- ions combine with H+ ions producing molecules of water. In order to maintain the constancy of Kb, some more undissociated molecules of BOH dissociates to produce exactly the same number of free OH- ions. This is called reverse basicity.

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