Solubility Product Constant, Ksp

One way to establish equilibrium between a slightly soluble solid and its ions in solution is to stir the solid with water to form a saturated solution. As you might expect, the solubility of the solid, s, in moles per liter, is related to the solubility product constant, Ksp. In the case of barium sulfate dissolving in water we have... 

The equilibrium constant expression associated with systems of slightly soluble salts is the solubility product constant, Ksp. It is the product of the ionic concentrations, each one raised to the power of the coefficient in the balanced chemical equation. It contains no denominator since the concentration of a solid is, by convention, 1, and for this reason it does not appear in the equilibrium constant expression. The Ksp expression for the PbS04 system is ... 

The solubility product constant, Ksp, is the equilibrium constant expression for sparingly soluble salts. It is the product of the ionic concentration of the ions, each raised to the power of the coefficient of the balanced chemical equation. 

From the above expression the solubility product constant Ksp may be designated as ... 

In Chapter 9, as in most of Unit 4, you learned about equilibrium reactions. In this section, you analyzed precipitation reactions. You mainly examined double-displacement reactions—reactions in which two soluble ionic compounds react to form a precipitate. You used the solubility product constant, Ksp, to predict whether or not a precipitate would form for given concentrations of ions. In Unit 5, you will learn about a class of reactions that will probably be new to you. You will see how these reactions interconvert chemical and electrical energy. 

Write the equation for the slight dissolution of the insoluble compound and calculate the AG°(reaction) using Equation (6) from Chapter 2. Once the AG°(reaction) value is obtained, the K value is calculated using Equation (8) also from Chapter 2. Keeping in mind that the concentration (activity) of the insoluble compound is defined as 1, it is recognized that the K value for the dissolution of the insoluble compound is the solubility product constant, Ksp. Alternatively, the Ksp value may be available from compilations of such values as presented in Lange s Handbook of Chemistry or the CRC Handbook of Chemistry and Physics. ... 

The solubility of an ionic compound can be described quantitatively by a value called the solubility product constant, Ksp. For the general solubility process AaBi, a An+ +b Bm, Ksp = [A, +HBm"]6. The brackets refer to concentrations in moles per liter. 

As an alternative to laboratory solubility measurements, solubility product constants (KSp), which are derived from thermodynamic data, can be used to calculate the solubility of solids in water (Table 2.9). Each solubility product constant describes a disassociation of a solid in water and calculates the activities or concentrations of the dissolution products in the saturated solution. The solubility product constant or another equilibrium constant of a reaction may be derived from the Gibbs free energy of the reaction (AG"K) as shown in the following equation ... 

Table 2.9 Equilibrium constants (including some solubility product constants, Ksp values, from Lide (2007), Krause and Ettel (1988), Bothe and Brown (1999), Davis (2000), Nordstrom and Archer (2003), Langmuir, Mahoney and Rowson (2006), Lee and Nriagu (2007), Zhu et al. (2005), and Zhu et al. (2006)) for reactions with various arsenic compounds in water at 1 bar pressure. pK = -logw K. ... 

The solubility product constant (Ksp) of EDTA was determined by adjusting the pH of an aqueous solution to a low value using nitric acid, and leaving the system to reach equilibrium overnight at room temperature. The precipitate was filtered off, dried at 105°C, and weighed to determine the amount of solubilized material. Alternatively, the precipitate was analyzed by complexometric titration, using standardized 0.05 M Zn(II) solution and xylenol orange as indicator [12]. The estimated value of the solubility product is 10 24 66 (pKsp = 24.66). 

Solubility product constant (Ksp) Equilibrium constant for the dissolution of a compound. 

In this chapter, we will extend the concepts of equilibrium that have been discussed in previous chapters. In Chapter 10 we discussed the concept of equilibrium in relation to saturated solutions in which an equilibrium was established between solvated ions and undissolved solute. In Chapter 11 we discussed the solubility of different salts when we looked at the formation of precipitates. In this chapter you will see the connection between these two ideas with the introduction of the solubility product constant, Ksp, which is a quantitative means of describing solubility equilibria. This measure helps to predict and explain the precipitation of different salts from solution. You will also see how the common-ion effect, temperature, and pH affect solubility. 

This equilibrium is known as a heterogeneous equilibrium, which is to say that it consists of substances that are in different states (phases). If you recall from Chapter 13, the equilibrium constant expressions for such equilibria do not contain the concentrations of liquids or solids. The equilibrium expression for this reaction will describe the degree to which the solid dissolves in solution, which is another way to say the degree to which it is soluble. And since the solid is not shown in the equilibrium expression, the equilibrium constant will express the product of the concentrations of the dissolved solute ions. For this reason, the equilibrium constant is referred to as the solubility-product constant. For this equilibrium, the solubility-product constant, Ksp is ... 

It is important to make the distinction between solubility and the solubility product constant. Solubility refers to the amount of a substance that can dissolve to form a saturated solution. The solubility of a substance is usually expressed in grams solute per liter of solution (g/L). Sometimes, however, it is described in moles solute per liter of solution, in which case it is referred to as the molar solubility of the substance. At any given temperature, the solubility-product constant, Ksp, for a solute remains constant. The solubility of a solute is not necessarily constant because it is affected by the concentrations of other dissolved substances. In the next section we will look at some factors that affect the solubility of a solute. 

The equilibrium between ionic solutes and their constituent ions can be summarized using the equilibrium constant known as the solubility product constant, Ksp. 

Because for a solid phase AB the activity is assumed to be constant at 1, the equilibrium constant of the mass-action law results in a solubility product constant (Ksp) or ion-activity product (IAP) as below ... 

The logarithm of the quotient of the ion activity product (IAP) and solubility product constant (KSP) is called the saturation index (SI). The IAP is calculated from activities that are calculated from analytically determined concentrations by considering the ionic strength, the temperature, and complex formation. The solubility product is derived in a similar manner as the IAP but using equilibrium solubility data corrected to the appropriate water temperature. 

Calculate the solubility-product constant, Ksp, of lead(II) chloride, PbCl2, which has a solubility of 1.00 g/100.0 g H2O at a temperature other than 25 °C. 

The Solubility-Product Constant (Ksp) Calculations Involving Ksp The Effect of a Common Ion The Effect of pH Qsp rs. K ... 

Background By observing the formation of two precipitates in the same system, you can infer the relationship between the solubilities of the two ionic compounds and the numerical values of their solubility product constants Ksp). 

The solubility of a substance can change considerably in response to a number of factors. For example, the solubilities of hydroxide salts, like Mg(OH)2, are dependent upon the pH of the solution. The solubility is also affected by concentrations of other ions in solution, especially common ions. In other words, the numeric value of the solubility of a given solute does change as the other species in solution change. In contrast, the solubility-product constant, Ksp, has only one value for a given solute at any specific temperature. A Figure 17.16 summarizes the relationships among various expressions of solubility and K p. 

To what reaction does the solubility product constant, Ksp, refer Table 16.1 lists /Tsp values for several ionic solids. For any of these ionic compounds, you should be able to calculate the solubility. What is the solubility of a salt, and what procedures do you follow to calculate the solubility of a salt How would you calculate the Ksp value for a salt given the solubility ... 

The Solubility-Product Constant, Ksp The solubility-product constant of an ionic compound is the equilibrium constant for the chemical equation that describes the dissolving of the compound. 

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