K_(sp), the "sp" stands for "solubility product", is another equilibrium constant, and measures the solubility of an insoluble or sparingly soluble salt. As with any equilibrium, standard conditions are assumed, i.e. 298*K, and 1*atm pressure.
The larger the K_(sp) constant, the more soluble is the salt. Silver halides are the classic insoluble salts, and K_(sp) measures the extent of the following reaction:
Ag^(+) + X^(-) rarr AgX(s) darr
K_(sp) = [Ag^+][X^-] (of course [AgX(s)] does not appear in this equilibrium expression in that we cannot speak of the concentration of a solid.
K_(sp), AgX: X=Cl, 1.8xx10^-10;
X=Br, 5.0xx10^(-13);
X=I, 8.5xx10^(-17)
From the list, it is clear that AgI is the least soluble species.
K_(sp) are extensively tabulated, especially for salts of precious metals. How do you think K_(sp) values would evolve at higher temperatures? Say. 323*K?
