General Organic and Biological Chemistry Fourth Edition Karen

Solutions: Solute and Solvent Solutions § are homogeneous mixtures of two or more substances. § contain a solute that is uniformly dispersed in another substance called the solvent. © 2013 Pearson Education, Inc. Chapter 8, Section 1 2

Nature of Solutes in Solutions Solutes § are spread uniformly throughout the solvent. § are not visible, but can give a color to the solution. § are usually present in a smaller amount than the solvent. © 2013 Pearson Education, Inc. Chapter 8, Section 1 3

Examples of Solutions The solute and solvent in a solution can be a solid,

Learning Check Identify the solute in each of the following solutions. 1. 2 g sugar and 100 m. L water 2. 60. 0 m. L of ethyl alcohol and 30. 0 m. L of methyl alcohol 3. 55. 0 m. L water and 1. 50 g Na. Cl 4. air: 200 m. L O 2 and 800 m. L N 2 © 2013 Pearson Education, Inc. Chapter 8, Section 1 5

Solution Identify the solute in each of the following solutions. Solute 1. 2 g sugar and 100 m. L water sugar 2. 60. 0 m. L of ethyl alcohol and 30. 0 m. L of methyl alcohol 3. 55. 0 m. L water and 1. 50 g Na. Cl 4. air: 200 m. L O 2 and 800 m. L N 2 O 2 © 2013 Pearson Education, Inc. Chapter 8, Section 1 6

Water § is the most common solvent in nature. § is a polar molecule. § forms hydrogen bonds between the partially positive hydrogen atom in one molecule and the partially negatively charged oxygen atom in a different water molecule. © 2013 Pearson Education, Inc. Chapter 8, Section 1 7

Water in the body § The average adult body contains 60% water by mass. § Dehydration occurs when as little as 10% of body fluids are lost. § Water lost can be replaced by liquids and foods in the diet. © 2013 Pearson Education, Inc. Chapter 8, Section 1 8

Formation of a Solution § To form a solution, the solute and solvent must have like polarities. § The energy between the solute and solvent particles must be strong enough to overcome the initial attractive forces between the solvent molecules and solute particles. © 2013 Pearson Education, Inc. Chapter 8, Section 1 9

Solutions with Ionic and Polar Solutes Na+ and Cl– ions § on the surface of a Na. Cl crystal are attracted to polar water molecules. § are hydrated in solution by many H 2 O molecules surrounding each ion. © 2013 Pearson Education, Inc. Chapter 8, Section 1 10

Equations for Solution Formation When Na. Cl(s) dissolves in water, the reaction can be

Learning Check Solid Li. Cl dissolves in water because: A. The Li+ ions are attracted to the oxygen atom ( ) of water. B. The Li+ ions are attracted to the hydrogen atom ( +) of water. C. The Cl– ions are attracted to the oxygen atom ( ) of water. D. The Cl– ions are attracted to the hydrogen atom ( +) of water. E. both A and D F. both B and C © 2013 Pearson Education, Inc. Chapter 8, Section 1 12

Solution Solid Li. Cl dissolves in water because: A. The Li+ ions are attracted to the oxygen atom ( ) of water. D. The Cl– ions are attracted to the hydrogen atom ( +) of water. E. both A and D © 2013 Pearson Education, Inc. Chapter 8, Section 1 13

Water and a Polar Solute Molecules of polar covalent compound methanol, CH 3 OH, form hydrogen bonds with polar water molecules to form a methanol–water solution. © 2013 Pearson Education, Inc. Chapter 8, Section 1 14

Like Dissolves Like Two substances form a solution when § there is an attraction between the particles of the solute and solvent. § a polar solvent, such as water, dissolves polar solutes, such as sugar and/or ionic solutes, such as Na. Cl. § a nonpolar solvent, such as hexane (C 6 H 14) dissolves nonpolar solutes, such as oil or grease. © 2013 Pearson Education, Inc. Chapter 8, Section 1 15

Like Dissolves Like Solvents Solutes Water (polar) CH 2 Cl 2 (nonpolar) Ni(NO 3)2

Learning Check Will each of the following solutes dissolve in water? Why or why

Solution Will each of the following solutes dissolve in water? Why or why not? A. B. C. D. Na 2 SO 4 gasoline I 2 HCl Yes, the solute is ionic. No, the solute is nonpolar. Yes, the solute is polar. Most polar and ionic solutes dissolve in water because water is a polar solvent. © 2013 Pearson Education, Inc. Chapter 8, Section 1 18