Precipitation and Dissolution Quiz

PDF page 817: The equilibrium constant for the equilibrium between a slightly soluble ionic solid and a solution of its ions is called the solubility product (Ksp) of the solid. Recall from the chapter on solutions and colloids that we use an ion’s concentration as an approximation of its activity in a dilute solution. For silver chloride, at equilibrium: − + − + AgCl(s) ⇌ Ag (aq) + Cl (aq) Ksp = [Ag (aq)][Cl (aq)] When looking at dissolution reactions such as this, the solid is listed as a reactant, whereas the ions are listed as products. The solubility product constant, as with every equilibrium constant expression, is written as the product of the concentrations of each of the ions, raised to the power of their stoichiometric coefficients. Here, the solubility

PDF page 817: product constant is equal to Ag and Cl when a solution of silver chloride is in equilibrium with undissolved AgCl. There is no denominator representing the reactants in this equilibrium expression since the reactant is a pure solid; therefore [AgCl] does not appear in the expression for Ksp. Some common solubility products are listed in Table 15.1 according to their Ksp values, whereas a more extensive compilation of products appears in Appendix J. Each of these equilibrium constants is much smaller than 1 because the compounds listed are only slightly soluble. A small Ksp represents a system in which the equilibrium lies to the left, so that relatively few hydrated ions would be present in a saturated solution. Common Solubility Products by Decreasing Equilibrium Constants Substance Ksp at 25 °C –6

PDF page 817: product constant is equal to Ag and Cl when a solution of silver chloride is in equilibrium with undissolved AgCl. There is no denominator representing the reactants in this equilibrium expression since the reactant is a pure solid; therefore [AgCl] does not appear in the expression for Ksp. Some common solubility products are listed in Table 15.1 according to their Ksp values, whereas a more extensive compilation of products appears in Appendix J. Each of these equilibrium constants is much smaller than 1 because the compounds listed are only slightly soluble. A small Ksp represents a system in which the equilibrium lies to the left, so that relatively few hydrated ions would be present in a saturated solution. Common Solubility Products by Decreasing Equilibrium Constants Substance Ksp at 25 °C –6

PDF page 816: time, Ag and Cl ions in the solution combine to produce an equal amount of the solid. At equilibrium, the opposing processes have equal rates.

PDF page 817: The equilibrium constant for the equilibrium between a slightly soluble ionic solid and a solution of its ions is called the solubility product (Ksp) of the solid. Recall from the chapter on solutions and colloids that we use an ion’s concentration as an approximation of its activity in a dilute solution. For silver chloride, at equilibrium: − + − + AgCl(s) ⇌ Ag (aq) + Cl (aq) Ksp = [Ag (aq)][Cl (aq)] When looking at dissolution reactions such as this, the solid is listed as a reactant, whereas the ions are listed as products. The solubility product constant, as with every equilibrium constant expression, is written as the product of the concentrations of each of the ions, raised to the power of their stoichiometric coefficients. Here, the solubility

PDF page 818: (c) Mg(OH) (s) ⇌ Mg (aq) + 2OH (aq)

PDF page 818: K = [Mg ][OH ] sp 2 2+ + 3− 2+ + 3−

PDF page 818: (e) Ca (PO )3OH(s) ⇌ 5Ca (aq) + 3PO (aq) + OH (aq)

PDF page 818: K = [Ca ] [PO ] [OH ] sp 4 4 4 5

PDF page 818: Recall that the definition of solubility is the maximum possible concentration of a solute in a solution at a given temperature and pressure. We can determine the solubility product of a slightly soluble solid from that measure of its solubility at a given temperature and pressure, provided that the only significant reaction that occurs when the solid dissolves is its dissociation into solvated ions, that is, the only equilibrium involved is: m+ n− M p Xq(s) ⇌ pM (aq) + qX (aq) In this case, we calculate the solubility product by taking the solid’s solubility expressed in units of moles per liter (mol/L), known as its molar solubility.

PDF page 818: Recall that the definition of solubility is the maximum possible concentration of a solute in a solution at a given temperature and pressure. We can determine the solubility product of a slightly soluble solid from that measure of its solubility at a given temperature and pressure, provided that the only significant reaction that occurs when the solid dissolves is its dissociation into solvated ions, that is, the only equilibrium involved is: m+ n− M p Xq(s) ⇌ pM (aq) + qX (aq) In this case, we calculate the solubility product by taking the solid’s solubility expressed in units of moles per liter (mol/L), known as its molar solubility.

PDF page 818: The concentration of Ca in a saturated solution of CaF2 is 2.15 × 10 M; therefore, that of F is 4.30 ×

PDF page 818: 10 M, that is, twice the concentration of Ca . What is the solubility product of fluorite?

PDF page 819: As with other equilibrium constants, we do not include units with Ksp. Check Your Learning

PDF page 823: Tabulated Ksp values can also be compared to reaction quotients calculated from experimental data to tell whether a solid will precipitate in a reaction under specific conditions: Q equals Ksp at equilibrium; if Q is less than Ksp, the solid will dissolve until Q equals Ksp; if Q is greater than Ksp, precipitation will occur at a given temperature until Q equals Ksp.