Salts Ionic compounds solubility product

Other useful solid-state electrodes are based on silver compounds (particularly silver sulfide). Silver sulfide is an ionic conductor, in which silver ions are the mobile ions. Mixed pellets containing Ag2S-AgX (where X = Cl, Br, I, SCN) have been successfiilly used for the determination of one of these particular anions. The behavior of these electrodes is determined primarily by the solubility products involved. The relative solubility products of various ions with Ag+ thus dictate the selectivity (i.e., kt] = KSp(Agf)/KSP(Aw)). Consequently, the iodide electrode (membrane of Ag2S/AgI) displays high selectivity over Br- and Cl-. In contrast, die chloride electrode suffers from severe interference from Br- and I-. Similarly, mixtures of silver sulfide with CdS, CuS, or PbS provide membranes that are responsive to Cd2+, Cu2+, or Pb2+, respectively. A limitation of these mixed-salt electrodes is tiiat the solubility of die second salt must be much larger than that of silver sulfide. A silver sulfide membrane by itself responds to either S2- or Ag+ ions, down to die 10-8M level. 

Most lanthanide compounds are sparingly soluble. Among those that are analytically important are the hydroxides, oxides, fluorides, oxalates, phosphates, complex cyanides, 8-hydroxyquinolates, and cup-ferrates. The solubility of the lanthanide hydroxides, their solubility products, and the pH at which they precipitate, are given in Table 2. As the atomic number increases (and ionic radius decreases), the lanthanide hydroxides become progressively less soluble and precipitate from more acidic solutions. The most common water-soluble salts are the lanthanide chlorides, nitrates, acetates, and sulfates. The solubilities of some of the chlorides and sulfates are also given in Table 2. 

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. 

Solubility data are presented for practically all entries. Quantitative data are also given for some compounds at different temperatures. In general, ionic substances are soluble in water and other polar solvents while the non-polar, covalent compounds are more soluble in the non-polar solvents. In sparingly soluble, slightly soluble or practically insoluble salts, degree of solubility in water and occurrence of any precipitation process may be determined from the solubility product, Ksp, of the salt. The smaller the Ksp value, the less its solubility in water. 

The product of the reaction is a salt and has the structure shown. The properties given in the problem (soluble in polar solvents, high melting point) are typical of those of an ionic compound. 

In aqueous solutions of ionic compounds, the ions act independently of each other. Soluble ionic compounds are written as their separate ions. We must be familiar with the solubility rules presented in Chapter 8 and recognize that the following types of compounds are strong electrolytes strong acids in solution, soluble metallic hydroxides, and salts. (Salts, which can be formed as the products of reactions of acids with bases, include all ionic compounds except strong acids and bases and metalhc oxides and hydroxides.) Compounds must be both ionic and soluble to be written in the form of their separate ions. (Section 9.1)... 

In dilute aqueous solutions, it has been demonstrated experimentally for poorly soluble ionic salts (solubilities less than 0.01 molL ) that the mathematical product of the total molar concentrations of the component ions is a constant at constant temperature. This product, is called the solubility product. Thus for a saturated solution of a simple ionic compound AB in water, we have the dynamic equilibrium ... 

Table 16.2 lists the solubility products for a number of salts of low solubility. Soluble salts such as NaCl and KNO3, which have very large /fjp values, are not listed in the table for essentially the same reason that we did not include values for strong acids in Table 15.3. The value of indicates the solubility of an ionic compound— the smaller the value, the less soluble the compound in water. However, in using K,.p values to compare solubihties, you should choose compounds that have similar formulas, such as AgCl and ZnS, or Cap2 and Fe(OH)2.

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. 

Notice that in Table 8.1 and Figure 8.3 the term salt is used to mean ionic compound. Many chemists use the terms salt and ionic compound interchangeably. In Example 8.1, we will illustrate how to use the solubility rules to predict the products of reactions among ions. 

To what reaction does the solubility product constant, refer Table 16.1 lists sp 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 value for a salt given the solubility ... 

Whether and to what extent a salt precipitates is characterized by the solubility product Aisp. The solubility product should be recalled from general chemistry texts as the equilibrium constant describing the formation of a slightly soluble (or nearly insoluble) ionic compound from its component ions in solution. Consider... 

The solubility products of selected compounds are listed in Table 11.4. Solubility product expressions can be used only for sparingly soluble salts. They cannot be used (without modification) for very soluble salts (like sodium chloride) because the concentration of ions is so high that the ions influence each other and the effective concentration of ions is lower than their concentration in mol dm . The errors in using similar equations for slightly soluble ionic substances (such as calcium hydroxide) are smaller, but are still significant in accurate work. (Now try Exercise 1 IE.)... 

On occasions, the choice of solvent is limited by simple features of the starting materials and products, such as their solubility or reactivity. Simple examples are cases where an inorganic salt is a reagent ionic compounds are relatively insoluble in most organic solvents. Sodium bromide, for example, dissolves well in water, reasonably well in methanol, a little in ethanol, and hardly at aU in most other organic solvents. 

Solubility product Solubility product constant, iQp, reflects the relationship between dissolved species and precipitated species. Each ionic compound has its own solubility limit, which is the maximum amount of the compound that can remain in solution. IQp is commonly used in solubility calculations to determine the precipitation potential of mineral salts. Certain combinations of cations and anions form sparingly soluble salts in water, and scaling in RO/NF may occur when the salts are concentrated beyond their solubility limits. See Table 6.10. 

The solubility product, sp, is the equilibrium constant for the reaction in which a solid salt (an ionic compound) dissolves to give its constituent ions in solution. For example. 

An example of a precipitation reaction is the formation of bright yellow insoluble lead(II) chromate when we mix solutions of the soluble ionic compounds lead(II) nitrate and potassium chromate (Figure 6-4). The other product of the reaction is KNO3, a soluble salt. 

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)... 

When an acid reacts with a base, the product is called a salt. Salts are ionic compounds with a cationic portion that derives from the base and a negatively charged counterion that originates from the acid. As ionic compounds, they are generally highly water soluble, a property that accounts for the fact that most drugs are administered in salt form (Figure 4.6). 

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