15.2 Solvents and Solutes An aqueous solution is water that contains dissolved substances. In a solution, the dissolving medium is the solvent. In a solution, the dissolved particles are the solute.

Solvents and Solutes A solvent dissolves the solute. The solute becomes dispersed in the solvent. Solvents and solutes may be gases, liquids, or solids. Solute particles can be atoms, ions, or molecules. 15.2

The Solution Process Polar solvents such as water dissolve ionic compounds and polar compounds. Nonpolar solvents such as gasoline dissolve nonpolar compounds. 15.2

Molarity a.The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent. A dilute solution is one that contains a small amount of solute. A concentrated solution contains a large amount of solute. 16.2

Molarity a.Molarity (M) is the number of moles of solute dissolved in one liter of solution. b.To calculate the molarity of a solution, divide the moles of solute by the volume of the solution. 16.2

Molarity a.To make a 0.5-molar (0.5M) solution, first add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water. 16.2

Molarity a.Swirl the flask carefully to dissolve the solute. 16.2

Molarity a.Fill the flask with water exactly to the 1-L mark. 16.2

16.3

Sample Problem

Making Dilutions Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles of solute in solution does not change. 16.2

Making Dilutions a.The total number of moles of solute remains unchanged upon dilution, so you can write this equation. a.M 1 and V 1 are the molarity and volume of the initial solution, and M 2 and V 2 are the molarity and volume of the diluted solution. 16.2

16.4

Making Dilutions a.To prepare 100 ml of 0.40M MgSO 4 from a stock solution of 2.0M MgSO 4, a student first measures 20 mL of the stock solution with a 20-mL pipet. 16.2

Making Dilutions a.She then transfers the 20 mL to a 100-mL volumetric flask. 16.2

Making Dilutions a.Finally she carefully adds water to the mark to make 100 mL of solution. 16.2

Properties of Acids and Bases Acids a.Acids taste sour, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution. 19.1

Properties of Acids and Bases Bases a.Bases taste bitter, feel slippery, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution. 19.1

Acids and Bases 19.1

Acids and Bases a.Hydrochloric Acid

Acids and Bases Acids Acids that contain one ionizable hydrogen, such as nitric acid (HNO 3 ), are called monoprotic acids. Acids that contain two ionizable hydrogens, such as sulfuric acid (H 2 SO 4 ), are called diprotic acids. Acids that contain three ionizable hydrogens, such as phosphoric acid (H 3 PO 4 ) are called triprotic acids. 19.1

Acids and Bases 19.1

Arrhenius Acids and Bases Bases a.Hydroxide ions are one of the products of the dissolution of an alkali metal in water. 19.1

Acids and Bases 19.1

Acid-Base Reactions a.In general, the reaction of an acid with a base produces water and one of a class of compounds called salts. 19.4

Acid-Base Reactions a.Reactions in which an acid and a base react in an aqueous solution to produce a salt and water are generally called neutralization reactions. 19.4