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Does solubility product of a salt at a particular temperature is constant or varies for...

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kumarvaibhav123 | Student, Grade 11 | Salutatorian

Posted January 21, 2013 at 9:06 AM via web

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Does solubility product of a salt at a particular temperature is constant or varies for different sovlent or for solutions having different pH?

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jerichorayel | College Teacher | (Level 1) Senior Educator

Posted January 22, 2013 at 10:47 AM (Answer #1)

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The solubility of a salt at a particular temperature can vary with different pH. If the salt contains a specie which has a conjugate weak acid or base, or can react with additional `H^(+)`   or `OH^(-)`  , the solubility can be affected. Let me show you an example:

 

`AgCN <=> Ag^(+) (aq) + CN^(-) (aq)`  

 

If you add some acid, the pH of the solution will decrease and proton, `H^(+)` concentration will increase. Since `CN^(-)` is a conjugate of a weak acid `HCN`  , the solubility will vary. 

 

`CN^(-) (aq) + H^(+) (aq) <=> HCN (aq)`

 

Cyanide ion, `CN^(-)` will react with the added `H^(+)`   to form `HCN` . Consequently, cyanide ions will be depleted. Now as the cyanide ion is being consumed, `AgCN`   will be forced to shift the equilibrium to the right thus making `AgCN` more soluble.                  

         

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