General Properties of Aqueous Solutions

A solution is a homogeneous mixture of two or more substances. (Section 1.2) The substance present in the greatest quantity is usually called the solvent, and the other substances are called solutes they are said to be dissolved in the solvent. When a small amount of sodium chloride (NaCl) is dissolved in a large quantity of water, for example, water is the solvent and sodium chloride is the solute. 

Many of the reactions that you will study occur in aqueous solution. Water is called the universal solvent, because it dissolves so many substances. It readily dissolves ionic compounds as well as polar covalent compounds, because of its polar nature. Ionic compounds that dissolve in water (dissociate) form electrolyte solutions, which conduct electrical current owing to the presence of ions. The ions can attract the polar water molecules and form a bound layer of water molecules around themselves. This process is called solvation. Refer to the Solutions and Periodicity chapter for an in-depth discussion of solvation. 

Even though many ionic compounds dissolve in water, many others do not. If the attraction of the oppositely charged ions in the solid for each other is greater than the attraction of the polar water molecules for the ions, then the salt will not dissolve to an appreciable amount. If solutions containing ions such as these are mixed, precipitation will occur, because the strong attraction of the ions for each other overcomes the weaker attraction for the water molecules. 

As mentioned before, certain covalent compounds, like alcohols, readily dissolve in water because they are polar. Since water is polar, and these covalent compounds are also polar, water will act as a solvent for them (general rule of solubility Like dissolves like ). Compounds like alcohols are nonelectrolytes—substances that do not conduct an electrical current when dissolved in water. However, certain covalent compounds, like acids, will ionize in water, that is, form ions  

There are several ways of representing reactions that occur in water. Suppose, for example, that we were writing the equation to describe the mixing of a lead(II) nitrate solution with a sodium sulfate solution and showing the resulting formation of solid lead(II) sulfate. One type of equation that can be written is the molecular equation, in which both the reactants and products are shown in the undissociated form  

Molecular equations are quite useful when doing reaction stoichiometry problems (see Chapter 7). 

Many chemical reactions and virtually all biological processes take place in an aqueous environment. Therefore, it is important to understand the properties of dilferent substances in solution with water. To start with, what exactly is a solution A solution is a homogeneous mixture of two or more substances. The substance present in a smaller amount is called the solute, whereas the substance present in a larger amount is called the solvent A solution may be gaseous (such as air), solid (such as an alloy), or hqrrid (seawater, for example). In this section we will discuss only aqueous solutions, in which the solute initially is a liquid or a solid and the solvent is water. 

What this equation says is that all the sodium chloride that enters the aqueous solution ends up as Na and Cl ions there are no undissociated NaCl units in solution. 

Strong Electrolytes, Weak 0 Qectrolyt and Nonelectrolytes ARIS, Anmations 

An arrangement for distinguishing between electrolytes and nonelectrolytes. A solution s ability to conduct electricity depends on the number of ions it contains, (a) A nonelectrolyte solution does not contain ions, and the lightbulb is not lit. 

Acids and bases are also electrolytes. Some acids, including hydrochloric acid (HCl) and nitric acid (HNO3), are strong electrolytes. These acids ionize completely in water for example, when hydrogen chloride gas dissolves in water, it forms hydrated H and Cr ions  

A solution is a homogeneous mixture [ W Section 1.2] of two or more substances. Solutions may be gaseous (such as air), soUd (such as brass), or liquid (such as saltwater). Usually, the substance present in the largest amount is referred to as the solvent and any substance present in a smaller amount is called the solute. For example, if we dissolve a teaspoon of sugar in a glass of water, water is the solvent and sugar is the solute. In this chapter we will focus on the properties of aqueous solutions—those in which water is the solvent. Throughout the remainder of this chapter, unless otherwise noted, solution will refer specifically to an aqueous solution. 

Student Annotation Bases may be molecular, like ammonia (NH3), or ionic, like sodium hydroxide (NaOH). 

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GENERAL PROPERTIES OF AQUEOUS SOLUTIONS (INTRODUCTION AND SECTION 4.1) Solutions in which water is the dissolving medium are called aqueous solutions. The component of the solution that is present in the greatest quantity is the solvent. The other components are solutes. 

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