Using ksp to Determine Molar Solubility

Recall from Section 13.3 that the solubility of a compoimd is the amount of the compoxmd that dissolves in a certain amoxmt of liquid. The molar solubility is the solubility in units of moles per liter. The molar solubility of a compound can be calculated directly from R p. For example, consider silver chloride. 

How can we find the molar solubility of AgCl from K p First, notice that K p is not the molar solubility it is the solubility-product constant. 

Second, notice that the concentration of either Ag or CP at equilibrium will be equal to the amoimt of AgCl that dissolved. We know this from the relationship of the stoichiometric coefficients in the balanced equation. 

Consequently, to find the solubility, we simply need to find [Ag ] or [Cl ] at equilibrium. We can do this by writing the expression for the solubility-product constant. 

Because both Ag and Cl come from AgCl, their concentrations must be equal. Since the solubility of AgCl is equal to the equilibrium concentration of either dissolved ion, we write  

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