Slightly soluble ionic compounds solubility-product constant

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

The dissolution in water of a slightly soluble ionic compound reaches an equilibrium characterized by a solubility-product constant, Kgp, that is much less than 1. Addition of a common ion lowers such a compound s solubility. Lowering the pH (adding HsO" ) increases the solubility if the anion of the ionic compound is that of a weak acid. 

Solubility-Product Constants (fCjp) of Slightly Soluble Ionic Compounds... 

In general, the solubility product constant (Aq,) is the equilibrium constant for the solubility equilibrium of a slightly soluble (or nearly insoluble) ionic compound. It equals the product of the equilibrium concentrations of the ions in the compound, each concentration raised to a power equal to the number of such ions in the formula of the compound. Like any equilibrium constant, K p depends on the temperature, but at a given temperature it has a constant value for various concentrations of the ions. ... 

The solubility product constant, K p, of a slightly soluble ionic compound is expressed in terms of the molar concentrations of ions in the saturated solution. These ion concentrations are in turn related to the molar solubility of the ionic compound, which is the moles of compound that dissolve to give a liter of saturated solution. The next two examples show how to determine the solubility product constant from the solubility of a slightly soluble ionic compound. 

These examples illustrate the relationship between the solubility of a slightly soluble ionic compound in pure water and its solubility product constant. In the next section, you will see how the solubility product constant can be used to calculate the solubility in the presence of other ions. K p is also useful in deciding whether to expect precipitation under given conditions. 

Calculating the solubility of a slightly soluble salt in a solution of a common ion Given the solubility product constant, calculate the molar solubility of a slightly soluble ionic compound in a solution that contains a common ion. (EXAMPLE 18.5)... 

Solubility-product constant (Xj ) the equilibrium constant for the solubility equilibrium of a slightly soluble (or nearly insoluble) ionic compound. (18.1)... 

Because each AgCl unit contains only one Ag and one CF ion, its solubility product expression is particularly simple to write. Many ionic compounds dissociate into more than two ions. Table 17.4 lists a number of slightly soluble ionic compounds along with equations representing their dissolution equilibria and their solubility product constants. (Compounds deemed soluble by the solubility rules in Chapter 4 are not listed for the same reason we did not list values for the strong acids in Table 16.6.) In general, the magnitude of indicates the solubility of an ionic compound—the smaller the value, the less soluble the compound. To make a direct... 

The solubility product constant (Kgp) is the equilibrium constant that indicates to what extent a slightly soluble ionic compound dissociates in water. 

In Chapter 4, we learned that a precipitation reaction can occur upon the mixing of two solutions containing ionic compounds when one of the possible cross products—the combination of a cation from one solution and the anion from the other—is insoluble. In this chapter, however, we have seen that the terms soluble and insoluble are extremes in a continuous range of solubihty—many compounds are slightly soluble and even those that we categorized as insoluble in Chapter 4 actually have some limited degree of solubihty (they have very small solubility product constants). 

The solubility of a substance is the concentration of its saturated solution. The solubility product constant, Kgp, is the equilibrium constant that describes the formation of a saturated solution of a slightly soluble ionic compound. It is the product of ionic concentrations, with each term raised to an appropriate power. 

As an approximation, the dissolved portion of a slightly soluble salt dissociates completely into ions. In a saturated solution, the ions are in equilibrium with the solid, and the product of the ion concentrations, each raised to the power of its subscript in the compound s formula, has a constant value (Qsp = K p). The value of K p can be obtained from the solubility, and vice versa. Adding a common ion lowers an ionic compound s solubility. Adding HgO" (lowering the pH) increases a compound s solubility if the anion of the compound is that of a weak acid. If Qsp > K p for an ionic compound, a precipitate forms when two solutions, each containing one of the compound s ions, are mixed. Lakes bounded by limestone-rich soils form buffer systems that prevent harmful acidification by acid rain. 

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... 

---