Solutes solubility product constant

Note that the brackets, [ ], refer to the concentration of the species. K,p is the solubility product constant hence [Cu " ] and [OH] are equal to the molar concentrations of copper and hydroxyl ions, respectively. The K p is commonly used in determining suitable precipitation reactions for removal of ionic species from solution. In the same example, the pH for removal of copper to any specified concentration can be determined by substituting the molar concentration into the following equation ... 

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 general approach illustrated by Example 18.7 is widely used to determine equilibrium constants for solution reactions. The pH meter in particular can be used to determine acid or base equilibrium constants by measuring the pH of solutions containing known concentrations of weak acids or bases. Specific ion electrodes are readily adapted to the determination of solubility product constants. For example, a chloride ion electrode can be used to find [Cl-] in equilibrium with AgCl(s) and a known [Ag+]. From that information, Ksp of AgCl can be calculated. 

It is important to note that the solubility product relation applies with sufficient accuracy for purposes of quantitative analysis only to saturated solutions of slightly soluble electrolytes and with small additions of other salts. In the presence of moderate concentrations of salts, the ionic concentration, and therefore the ionic strength of the solution, will increase. This will, in general, lower the activity coefficients of both ions, and consequently the ionic concentrations (and therefore the solubility) must increase in order to maintain the solubility product constant. This effect, which is most marked when the added electrolyte does not possess an ion in common with the sparingly soluble salt, is termed the salt effect. 

If S moles of CaCC>3 dissolve in a liter of water, then S moles each of calcium ion and carbonate ion form. With these ion concentrations equal to S, the solubility of CaCC>3 is calculated as 9.3 x 10 5 M. The higher solubility of magnesium carbonate in water, 6.3 x 10 3 M, results from the larger solubility product constant. Nevertheless, both of these carbonate salts are rather insoluble, and the excess carbonate anions provided by the sodium carbonate effectively precipitate the calcium and magnesium ions from solution. 

B We first use the solubility product constant expression for Pbl2 to determine the [i" j needed in solution to just form a precipitate when [Pb2+] = 0.010 M. We assume that the volume of solution added is small and that [Pb2+] remains at 0.010 M throughout. 

The solubility of a compound refers to the concentration of that compound in solution, either as a molarity or as a mass per unit volume. The solubility product constant is the equilibrium constant in terms of concentrations of ions, for the dissolution equilibrium, raised to their appropriate coefficients. 

We first use the solubility product constant expression to determine [Pb2+] in a solution with 0.100 M Cl-. 

Normally we would worry about the mutual dilution of the two solutions, but the values of the solubility product constants are so small that only a very small volume of 0.50 M Pb(N03)2 solution needs to be added, as we shall see. 

Knowing the value of the solubility product constant can also allow us to predict whether or not a precipitate will form if we mix two solutions, each containing an ion component of a slightly soluble salt. We calculate the reaction quotient (many times called the ion product), which has the same form as the solubility product constant. We take into consideration the mixing of the volumes of the two solutions, and then compare this reaction quotient to the K.p. If it is greater than the Ksp then precipitation will occur until the ion concentrations reduce to the solubility level. 

The common-ion effect is an application of Le Chatelicr s principle to equilibrium systems of slightly soluble salts. A buffer is a solution that resists a change in pH if we add an acid or base. We can calculate the pH of a buffer using the Henderson-Hasselbalch equation. We use titrations to determine the concentration of an acid or base solution. We can represent solubility equilibria by the solubility product constant expression, Ksp. We can use the concepts associated with weak acids and bases to calculate the pH at any point during a titration. 

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). 

Sigma (a) bonds Sigma bonds have the orbital overlap on a line drawn between the two nuclei, simple cubic unit cell The simple cubic unit cell has particles located at the corners of a simple cube, single displacement (replacement) reactions Single displacement reactions are reactions in which atoms of an element replace the atoms of another element in a compound, solid A solid is a state of matter that has both a definite shape and a definite volume, solubility product constant (/ p) The solubility product constant is the equilibrium constant associated with sparingly soluble salts and is the product of the ionic concentrations, each one raised to the power of the coefficient in the balanced chemical equation, solute The solute is the component of the solution that is there in smallest amount, solution A solution is defined as a homogeneous mixture composed of solvent and one or more solutes. 

In this section, you determined the solubility product constant, Kgp, based on solubility data. You obtained your own solubility data and used these data to calculate a value for Kgp. You determined the molar solubility of ionic solutions in pure water and in solutions of common ions, based on their Ksp values. In section 9.3, you will further explore the implications of Le Chatelier s principle. You will use a reaction quotient, Qsp, to predict whether a precipitate forms. As well, you will learn how selective precipitation can be used to identify ions in solution. 

When equilibrium is reached, solubility product constants are used to describe saturated solutions of ionic compounds of relatively low solubility. When the ion concentration in solution reaches saturation, equilibrium between the solid and dissolved ions is established. 

BIOMINERALIZATION SOLUBILITY PRODUCT Solubility product constant, BIOMINERALIZATION Solute-solvent interactions,... 

It has long been recognized that ferric iron is a moderately strong acid. As early as 1896, Goodwin (5) concluded from conductometric measurements that simple dilution of ferric chloride solutions led to the formation of FeOH2+. The insolubility of ferric hydroxide has of course been appreciated even longer. The best current estimate of the solubility product constant for Fe OH)s at 25° (in 3 M NaC104) is (d). 

Metastability of Hydrolyzed Iron (III) Solutions The low solubility of ferric hydroxide has been alluded to in the Introduction. Feitknecht and Michaelis (29) have observed that aU ferric perchlorate solutions to which base has been added are unstable with respect to eventual precipitation of various forms of hydrated ferric oxides. In 3 M NaC104 at 25° C the two phase system reaches an apparent equilibrium after 200 hours, according to Biedermann and Schindler (6), who obtained a reproducible solubility product constant for ferric hydroxide at varying degrees of hydrolysis. It appears that many of the solutions used in the equilibrium studies of Hedstrom (9) and Biedermann (22) were metastable, and should eventually have produced precipitates. Nevertheless, since the measured potentials were reversible, the conclusions reached about the species present in solution remain valid. 

Chemists use a quantity called the solubility product constant, or to compare the solubilities of salts. AT p is calculated in much the same way as an equilibrium constant (K, see Chapter 14). The product concentrations are multiplied together, each raised to the power of its coefficient in the balanced dissociation equation. There s one key difference, however, between a and a is a quantity specific to a saturated solution of salt, so the con-... 

Thus the solution always contains Mg in approximately constant abundance, which makes it effectively a perfectly mobile component. The same is true for H+ since pH changes little after precipitation of the sepiolite even though the reaction consumes (OH). The experimental system is then "open" with respect to these two components. A determination of the solubility product constant of a natural iron-calcium-aluminous sepiolite confirms generally the above results (Christ, et al , 1973). 

Moeller et al. [294, 295] have thoroughly studied the pH values at which the rare earth hydroxides are precipitated from various salt solutions, and also the solubility and solubility product constants of the hydroxides. Their results are summarized in Table 18. 

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 ... 

Solubility product constant An equilibrium constant that describes the dissolution of a solid in water. Solute A substance that will dissolve into a solvent or that has dissolved into a solvent. 

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). 

The solubility-product constant, Ksp, is the equilibrium constant for an ionic solid in contact with a saturated aqueous solution. The two processes with equal rates in this case are dissolution and crystallization. 

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