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General Chemistry Principles, Patterns, and Applications, 2011

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Chapter 13<br />

Solutions<br />

We explored the general properties of gases, liquids, <strong>and</strong> solids in Chapter 10 "Gases",Chapter 11 "Liquids",<br />

<strong>and</strong> Chapter 12 "Solids", respectively. Most of the discussion focused on pure substances containing a single kind of<br />

atom, molecule, or cation–anion pair. The substances we encounter in our daily lives, however, are usually mixtures<br />

rather than pure substances. Some are heterogeneous mixtures, which consist of at least two phases that are not<br />

uniformly dispersed on a microscopic scale; others are homogeneous mixtures, consisting of a single phase in<br />

which the components are uniformly distributed. (For more information about homogeneous mixtures, see Chapter 1<br />

"Introduction to <strong>Chemistry</strong>", Section 1.3 "A Description of Matter".) Homogeneous mixtures are also<br />

called solutions; they include the air we breathe, the gas we use to cook <strong>and</strong> heat our homes, the water we drink, the<br />

gasoline or diesel fuel that powers engines, <strong>and</strong> the gold <strong>and</strong> silver jewelry we wear.<br />

Beads of oil in water. When a nonpolar liquid such as oil is dispersed in a polar solvent such as water, it<br />

does not dissolve, but forms spherical beads. Oil is insoluble in water because the intermolecular<br />

interactions within the solute (oil) <strong>and</strong> the solvent (water) are stronger than the intermolecular<br />

interactions between the solute <strong>and</strong> the solvent.<br />

Many of the concepts that we will use in our discussion of solutions were introduced in earlier chapters. In Chapter 4<br />

"Reactions in Aqueous Solution", for example, we described reactions that occur in aqueous solution <strong>and</strong> how to<br />

use molarity to describe concentrations. In Chapter 4 "Reactions in Aqueous Solution", Chapter 7 "The Periodic<br />

Table <strong>and</strong> Periodic Trends", <strong>and</strong> Chapter 11 "Liquids", we introduced the principles that govern ion–ion <strong>and</strong><br />

molecule–molecule interactions in pure substances; similar interactions also occur in solutions. Now we use the<br />

principles developed in those chapters to underst<strong>and</strong> the factors that determine how much of one substance can<br />

dissolve in another, <strong>and</strong> how the properties of a solution differ from those of its components.<br />

The properties of mixtures of gases were described in Chapter 10 "Gases", <strong>and</strong> the properties of certain types of solid<br />

solutions, such as alloys <strong>and</strong> doped semiconductors, were discussed in Chapter 12 "Solids". This chapter focuses on<br />

liquid solutions, aqueous or otherwise. By the end of this chapter, your underst<strong>and</strong>ing of solutions will enable you to<br />

explain why the radiator in your car must contain ethylene glycol to avoid damage to the engine on cold winter nights,<br />

why salt is spread on icy roads in the winter (<strong>and</strong> why it isn’t effective when the temperature is too low), why certain<br />

vitamins accumulate in your body at toxic levels while others are rapidly excreted, <strong>and</strong> how salt can be removed from<br />

seawater to provide drinking water.<br />

13.1 Factors Affecting Solution Formation<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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