How do you write the Ksp equation?

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Answer 1 · 2017-08-16T05:36:25

Well, for a start $K_"sp"=K_"solubility product"$ , and we use an equilibrium expression.

For the sparingly soluble salt, $MX$ , we write the equation that represents its dissolution:

$MX(s) stackrel(H_2O)rightleftharpoonsM^+ + X^-$

$K_"sp"=([M^+][X^-])/([MX(s)])$ , but $MX(s)$ as A SOLID cannot express a concentration, and thus the expression simplifies to...

$K_"sp"=[M^+][X^-]$

Usually standard conditions are specified, because a hot solution can generally hold more solute than a cold one.

For salts of the form $MX_2$ , $K_"sp"=[M^(2+)][X^-]^2$ . $K_"sp"$
have been measured for a host of insoluble, and semi-soluble ionic salts.

See [here for more detail.](https://socratic.org/questions/how-can-i-calculate-solubility-equilibrium)