Ionic compound solubility

Exploration of the Relationship between Ionic Compound Solubility and the Presence of Ions Common to the Solubility Equilibrium. 

Why are some ionic compounds soluble in water and others are not ... 

Repeat step 2. Are both ionic compounds soluble If so, go to step 4, if not, go back to step 2. 

Equilibria of Slightly Soluble Ionic Compounds Solubility-Product Constant K )... 

A problem that often arises in the laboratory is finding a solvent that will dissolve all the reactants needed for a given reaction. For example, if we want cyanide ion to react with 1-bromohexane, we must find a way of mixing sodium cyanide (an ionic compound soluble only in water) with the alkyl halide (an organic compound that is insoluble in water). If we mix an aqueous solution of sodium cyanide with a solution of the alkyl halide in a nonpolar solvent, there will be two distinct phases—an aqueous phase and a nonpolar phase— because the two solutions are immiscible. How, then, can a reaction between sodium cyanide and 1-bromohexane take place ... 

Prediction of solubility for simple ionic compounds is difficult since we need to know not only values of hydration and lattice enthalpies but also entropy changes on solution before any informed prediction can be given. Even then kinetic factors must be considered. 

It is soluble in organic solvents (a characteristic of a covalent compound). but dissolves in water and can form hydrates (a characteristic of an ionic compound), hence the hydrated must be... 

These chlorozincates must not be confused with the non-ionic compounds which quinoline and aniline bases give with neutral zinc chloride the latter have the formulae [(C,H7N)2ZnClt] and [(C,H7N)tZnCl ] respectively, and both are only slightly soluble in water. 

Solvent Effects on the Rate of Substitution by the S 2 Mechanism Polar solvents are required m typical bimolecular substitutions because ionic substances such as the sodium and potassium salts cited earlier m Table 8 1 are not sufficiently soluble m nonpolar solvents to give a high enough concentration of the nucleophile to allow the reaction to occur at a rapid rate Other than the requirement that the solvent be polar enough to dis solve ionic compounds however the effect of solvent polarity on the rate of 8 2 reactions IS small What is most important is whether or not the polar solvent is protic or aprotic Water (HOH) alcohols (ROH) and carboxylic acids (RCO2H) are classified as polar protic solvents they all have OH groups that allow them to form hydrogen bonds... 

The metal-ion complexmg properties of crown ethers are clearly evident m their effects on the solubility and reactivity of ionic compounds m nonpolar media Potassium fluoride (KF) is ionic and practically insoluble m benzene alone but dissolves m it when 18 crown 6 is present This happens because of the electron distribution of 18 crown 6 as shown m Figure 16 2a The electrostatic potential surface consists of essentially two regions an electron rich interior associated with the oxygens and a hydrocarbon like exterior associated with the CH2 groups When KF is added to a solution of 18 crown 6 m benzene potassium ion (K ) interacts with the oxygens of the crown ether to form a Lewis acid Lewis base complex As can be seen m the space filling model of this... 

A precipitation reaction occurs when two or more soluble species combine to form an insoluble product that we call a precipitate. The most common precipitation reaction is a metathesis reaction, in which two soluble ionic compounds exchange parts. When a solution of lead nitrate is added to a solution of potassium chloride, for example, a precipitate of lead chloride forms. We usually write the balanced reaction as a net ionic equation, in which only the precipitate and those ions involved in the reaction are included. Thus, the precipitation of PbCl2 is written as... 

In the absence of die polyether, potassium fluoride is insoluble in benzene and unreactive toward alkyl halides. Similar enhancement of solubility and reactivity of other salts is observed in the presence of crown ethers The solubility and reactivity enhancement result because the ionic compound is dissociated to a tightly complexed cation and a naked anion. Figure 4.13 shows the tight coordination that can be achieved with a typical crown ether. The complexed cation, because it is surrounded by the nonpolar crown ether, has high solubility in the nonpolar media. To maintain electroneutrality, the anion is also transported into the solvent. The cation is shielded from interaction with the anion as a... 

A soluble cyanide added to silver nitrate solution precipitates silver cyanide as an ionic compound ... 

Many, but not all, ionic compounds (e.g., NaCl but not CaC03) are soluble in water, a polar solvent In contrast, ionic compounds are insoluble in nonpolar solvents such as benzene (C6H6) or carbon tetrachloride (CCI4). 

As we noted in Chapter 4, the solubility of ionic compounds in water varies tremendously from one solid to another. The extent to which solution occurs depends on a balance between two forces, both electrical in nature ... 

Sulfide minerals and K. Sulfides are among the least soluble ionic compounds. Their AQ, values are often smaller than 10-25. For this reason, many sulfides are found as minerals, for example (clockwise from the left), iron pyrite (FeS2), yellow orpiment (AS2S3). and black galena (PbS). 

The reverse of Example 16.4 involves finding Rq, of a compound given its solubility. The solubilities of many ionic compounds are determined experimentally and tabulated in chemical handbooks. Most solubility values are given in grams of solute dissolved in 100 grams of water. To obtain the molar solubility in moles/L, we have to assume that the density of the solution is equal to that of water. Then the number of grams of solute per 100 g water is equal to the number of grams of solute per 100 mL of solution. This assumption is valid because the mass of the compound in solution is small. To solve for IQp, find the molar solubility of the solute and determine the concentration of its component ions. Substitute into the IQp expression. 

Let us apply these ideas to the third-row elements. On the left side of the table we have the metallic reducing agents sodium and magnesium, which we already know have small affinity for electrons, since they have low ionization energies and are readily oxidized. It is not surprising, then, that the hydroxides of these elements, NaOH and Mg(OH)z, are solid ionic compounds made up of hydroxide ions and metal ions. Sodium hydroxide is very soluble in water and its solutions are alkaline due to the presence of the OH- ion. Sodium hydroxide is a strong base. Magnesium hydroxide, Mg(OH)2, is not very soluble in water, but it does dissolve in acid solutions because of the reaction... 

In general, the compounds best separated by LSC are those which are soluble in organic solvents and are non-ionic. Water soluble non-ionic compounds are better separated using either reverse-phase or bonded-phase chromatography. 

Some ionic compounds are soluble, others are not. Consider what happens when we pour a solution of sodium chloride (a strong electrolyte) into a solution of silver nitrate (another strong electrolyte). A solution of sodium chloride contains Na+ cations and Cl anions. Similarly, a solution of silver nitrate, AgNO, contains Ag+ cations and NO, anions. When we mix these two aqueous solutions, a white precipitate, a cloudy, finely divided solid deposit, forms immediately. Analysis shows that the precipitate is silver chloride, AgCl, an insoluble white solid. The... 

Table 1.1 summarizes the solubility patterns of common ionic compounds in water. Notice that all nitrates and all common compounds of the Group 1 metals are soluble so they make useful starting solutions for precipitation reactions. Any spectator ions can be used, provided that they remain in solution and do not otherwise react. For example, Table 1.1 shows that mercury(I) iodide, Hg2I2, is insoluble. It is formed as a precipitate when solutions containing Hg22+ ions and I ions are mixed ... 

Use the information in Table 1.1 to classify each of the following ionic compounds as soluble or insoluble in water ... 

For each of the following reactions, suggest two soluble ionic compounds that, when mixed together in water, result in the net ionic equation given ... 

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