Dissolving ionic compound in water

In contrast to sugar, solid sodium chloride dissolves in water to give a liquid that conducts electricity. Figure 3-19 shows that a solution of NaCl is a good conductor. When an ionic compound dissolves in water, its component cations and anions are free to move about in the solution. Mixing leads to a uniform distribution of Na and Cl ions through the entire solution, with each ion surrounded by a sheath of water molecules as shown in Figure 3-20. 

In cases where the solvation energies are large, as for example when ionic compounds dissolve in water, these hydrophobic effects, based on adverse changes in entropy, are swamped. Dissolving such compounds can be readily accomplished due to the very large energies released when the ions become hydrated. 

When ionic compounds dissolve in water, the ions in the crystal separate and move throughout the solution. When two such solutions are mixed, all types of positive ions in the new solution are attracted to all types of negative ions in the solution. Sometimes a reaction takes place. This reaction is called a double-replacement reaction. Double-replacement reactions are sometimes called ionic reactions. 

When an ionic compound dissolves in water, energy is needed to break the ionic bonds of the crystal. As the ions attach to the water molecules and become hydrated, energy is released. The process is endothermic if the energy needed to break the bonds is greater than the energy released when the ions attach to water. 

Many of the reactions that you will study occur in aqueous solution. Water readily dissolves many ionic compounds as well as some covalent compounds. Ionic compounds that dissolve in water (dissociate) form electrolyte solutions— solutions that conduct electrical current due to the presence of ions. We may classify electrolytes as either strong or weak. Strong electrolytes dissociate (break apart or ionize) completely in solution, while weak electrolytes only partially dissociate. Even though many ionic compounds dissolve in water, many do not. If the attraction of the oppositely charged ions in the solid is greater than the attraction of the water molecules to the ions, then the salt will not dissolve to an appreciable amount. 

Whether an ionic compound dissolves in water depends on the strength of the ionic bond holding the compound together. Water must have sufficient strength to break the ionic bond. The strength of the... 

Show that most ionic compounds dissolve in water. 

It is a remarkable thing for an ionic compound to dissolve in water. You probably learned at some point that opposite charges attract each other. The energy cost of separating positively charged cations from negatively charged anions is immense. Dissolution occurs only because water interacts very effectively with ions. We will explore this phenomenon more fully in chapter 8. For now, however, you just need to accept that when ionic compounds dissolve in water, they (mostly) separate into ions that freely and independently move around in the solution. Since these ions are free to move around in the solution, the solution conducts electricity. 

When ionic compounds dissolve in water, the resulting solution contains the separated ions. 

Complete ionic (remember that any ionic compound dissolved in water will be present as the separated ions) ... 

When ionic compounds dissolve in water, the ions separate from each other and spread throughout the solution. Thus, the formulas Kl(a ) and Fb(NOs)2(aq) are actually aqueous ions, as shown below. 

In addition to molecular compounds, ionic compounds may be solutes in aqueous solutions. Recall from Chapter 8 that ionic compounds consist of positive ions and negative ions held together by ionic bonds. When ionic compounds dissolve in water, their ions can separate. The equation below shows an aqueous solution of the ionic compound sodium hydroxide. 

You are given two clear, colorless solutions, and you are told that one solution consists of an ionic compound dissolved in water and the other consists of a covalent compound dissolved in water. How could you determine which is an ionic solution and which is a covalent solution ... 

Remember how a model made it easier for us to picture the structures of solids, liquids, and gases in Chapter 2 In order to develop a mental image of the changes that take place on the microscopic level as an ionic compound dissolves in water, chemists have found it helpful to extend that model. We will use table salt or sodium chloride, NaCl, as an example in our description of the process through which an ionic compound dissolves in water. Before you read about this process, you might want to return to the end of Section 3.3 and review the description of the structure of liquid water. 

When an ionic compound dissolves in water, the ions that escape the solid are... 

Describe the process by which an ionic compound dissolves in water, referring to the nature of the particles in solution and the kind of attractions that form between them. (Section 4.2.)... 

QUGStionS process by which this ionic compound dissolves in water, including the nature of... 

As pointed out earlier, when ionic compounds dissolve in water, they break apart completely into their component cations and anions. To be more realistic, the equations should show the dissociation of dissolved ionic compounds into ions. Therefore, returning to the reaction between sodium iodide and lead nitrate, we would write... 

Figure 4,2 The dissolution of an ionic compound. When an ionic compound dissolves in water, H2O molecules separate, surround, and disperse the ions into the liquid. The negative ends of the H2O molecules face the positive ions and the positive ends face the negative ions.

Although many ionic compounds dissolve in water, many others do not. In the latter cases, the electrostatic attraction among ions in the compound remains greater than the attraction between ions and water molecules, so the solid stays largely intact. Actually, these so-called insoluble substances do dissolve to a very small extent, usually several orders of magnitude less than so-called soluble substances. Compare, for example, the solubilities of NaCl (a soluble compound) and AgCl (an insoluble compound) ... 

Water plays an active role in dissolving ionic compounds because it consists of polar molecules that are attracted to the ions. When an ionic compound dissolves in water, the ions dissociate from each other and become solvated by water molecules. Because the ions are free to move, their solutions conduct electricity. Water also dissolves many covalent substances with polar bonds. It interacts with some H-containing molecules so strongly it breaks their bonds and dissociates them into IT faq) ions and anions. In water, the ion is bonded to an H2O, forming HaO . ... 

When an ion and a nearby polar moleeule (dipole) attraet eaeh other, an ion-dipole force results. The most important example takes plaee when an ionic compound dissolves in water. The ions become separated because the attractions between the ions and the oppositely charged poles of the H2O molecules overcome the attractions between the ions themselves. Ion-dipole forces in solutions and their associated energy are discussed fully in Chapter 13. 

Figure 13.2 Hydration shells around an aqueous ion. When an ionic compound dissolves in water, ion-dipole forces orient water molecules around the separated ions to form hydration shells. The cation shown here is octahedrally surrounded by six water molecules, which form H bonds with water molecules in the next hydration shell, and those form H bonds with others farther away.

What Happens When an Ionic Compound Dissolves in Water ... 

Electrical conductivity of aqueous solutions. The result of this experiment is strong evidence that ionic compounds dissolved in water exist in the form of separated ions. 

When Ionic compounds dissolve In water, the resuiting soiution contains the separated ions. 

Strategy Recall that an ionic equation shows dissolved ionic compounds in tenns of their free ions. A net ionic equation shows only the species that actually take part in the reaction. What happens when ionic compounds dissolve in water What ions are formed from the dissociation of NaaS and ZnCh What happens when the cations encounter the anions in solution ... 

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