Equilibria of Slightly Soluble Ionic Compounds

In this section, we explore the aqueous equilibria of slightly soluble ionic compounds, which up to now we ve called insoluble. In a saturated solution at a particular temperature, equilibrium exists between the undissolved and dissolved solute (Chapter 13). Slightly soluble ionic compounds have a relatively low solubility, so they reach equilibrium with relatively little solute dissolved. At this point, it would be a good idea for you to review the solubility rules listed in Table 4.1. 

If we make the assumption that there is complete dissociation of a slightly soluble ionic compound into its component ions, then equilibrium exists between solid solute and aqueous ions. Thus, for example, for a saturated solution of lead(II) sulfate in water, we have 

As with all the other equilibrium systems we ve looked at, this one can be expressed by a reaction quotient  

As in previous cases, we incorporate the constant concentration of the solid, [PbS04], into the value of Q, which gives the ion-product expression, Q p. 

when solid PbS04 attains equilibrium with Pb and S04 ions, that is, when the solution reaches saturation, the numerical value of Q p attains a constant value, called the solubility-product constant, K p. The K p for PbS04 at 25°C, for example, is 1.6X10  

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Equilibria of Slightly Soluble Ionic Compounds The Sobbility-Product Constant (K p) Calculations Involving The Effect of a Common Ion The Effect of pH Csp vs. Kgp... 

Equilibria of Slightly Soluble Ionic Compounds Solubility-Product Constant K )... 

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