THE SOLUBILITY PRODUCT CONSTANT

Once the composition of the aqueous solution phase has been determined, the activity of an electrolyte having the same chemical formula as the assumed precipitate can be calculated (11,12). This calculation may utilize either mean ionic activity coefficients and total concentrations of the ions in the electrolyte, or single-ion activity coefficients and free-species concentrations of the ions in the electrolyte (11). If the latter approach is used, the computed electrolyte activity is termed an ion-activity product (12). Regardless of which approach is adopted, the calculated electrolyte activity is compared to the solubility product constant of the assumed precipitate as a test for the existence of the solid phase. If the calculated ion-activity product is smaller than the candidate solubility product constant, the corresponding solid phase is concluded not to have formed in the time period of the solubility measurements. Ihis judgment must be tempered, of course, in light of the precision with which both electrolyte activities and solubility product constants can be determined (12). 

The model balance equation for each metal and ligand (e.g., Eqs. 2.49 and 2.52) is augmented to include formally the concentration of each possible solid phase. By choosing an appropriate linear combination of these equations, it is always possible to eliminate the concentrations of the solid phases from the set of equations to be solved numerically. Moreover, some of the free ionic concentrations of the metals and ligands also can be eliminated from the equations because of the constraints imposed by on their activities (combine Eqs. 3.2 and 3.3), which holds for each solid phase formed. The final set of nonlinear algebraic equations obtained from this elimination process will involve only independent free ionic concentrations, as well as conditional stability and solubility product constants. The numerical solution of these equations then proceeds much like the iteration scheme outlined in Section 2.4 for the case where only complexation reactions were considered, with the exception of an added requirement of self-consistency, that the calculated concentration of each solid formed be a positive number and that IAP not be greater than Kso (see Fig. 

Solubility Solubility Product Constant The ability of a substance to dissolve in another substance. The equilibrium constant of a slightly soluble salt. 

Solubility product constant the constant for the equilibrium expression representing the dissolving of an ionic solid in water. (8.8)... 

Solubility product constant—The term given to the equilibrium constant when products are in equilibrium with solid reactants. 

Solubility product constant—The product of the concentrations of ions, raised to appropriate powers, in equilibrium with their solid. 

The product of and the concentration of the undissolved solid creates a new constant called the solubility product constant, The solubility product constant is an equilihrium constant for the dissolving of a sparingly soluble ionic compound in water. The solubility product constant expression is... 

Using solubility product constants The solubility product constants in Table 18-3 have been determined through careful experiments. values are... 

In equilibria that involve slightly soluble compounds in water, the equilibrium constant is called a solubility product constant, The activity of the solid BaSO is one (Section... 

Solubility product constant, The equilibrium constant that applies to the dissolution of a slightly soluble compound. 

Solubility product constant the constant for the equilibrium expression representing the dissolving of an ionic solid in water. (16.1) Solute a substance dissolved ina liquid to form a solution. (4.2 11.1) Solution a homogeneous mixture. (1.9)... 

Using solubility product constants The solubility product constants in Table 17.3 have been determined through careful experiments. Ksp values are important because they can be used to determine the solubility of a sparingly soluble compound. Recall that the solubility of a compound in water is the amount of the substance that will dissolve in a given volume of water at a given temperature. 

It is important to distinguish carefully between solubility and the solubility-product constant. The solubility of a substance is the quantity that dissolves to form a saturated solution. (Section 13.2) Solubility is often expressed as grams of solute per liter of Solution (g/L). Molar solubility is the number of moles of solute that dissolve in forming 1 L of saturated solution of the solute (mol/L). The solubility-product constant (K p) is the equilibrium constant for the equilibrium between an ionic solid and its saturated solution and is a unitless number. Thus, the magnitude of is a measure of how much of the solid dissolves to form a saturated solution. 

The Solubility-Product Constant, The solubility-product constant reflects the solubility of a compound. The greater the solubility-product constant, the greater the solubility of the compound. 

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