General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 8 Solutions 8.1 Solutions Lectures © 2013 Pearson Education, Inc.

Solutions: Solute and Solvent are homogeneous mixtures of two or more substances. contain a solute that is uniformly dispersed in another substance called the solvent.

Nature of Solutes in Solutions 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.

Examples of Solutions The solute and solvent in a solution can be a solid, liquid, and/or a gas.

Learning Check Identify the solute in each of the following solutions. 1. 2 g sugar and 100 mL water 2. 60.0 mL of ethyl alcohol and 30.0 mL of methyl alcohol 3. 55.0 mL water and 1.50 g NaCl 4. air: 200 mL O2 and 800 mL N2

Solution Identify the solute in each of the following solutions. 1. 2 g sugar and 100 mL water sugar 2. 60.0 mL of ethyl alcohol and 30.0 mL of methyl alcohol methyl alcohol 3. 55.0 mL water and 1.50 g NaCl NaCl 4. air: 200 mL O2 and 800 mL N2 O2

Water 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.

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.

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.

Solutions with Ionic and Polar Solutes Na+ and Cl– ions on the surface of a NaCl crystal are attracted to polar water molecules. are hydrated in solution by many H2O molecules surrounding each ion.

Equations for Solution Formation When NaCl(s) dissolves in water, the reaction can be written as:

Learning Check Solid LiCl 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

Solution Solid LiCl 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

Water and a Polar Solute Molecules of polar covalent compound methanol, CH3OH, form hydrogen bonds with polar water molecules to form a methanol–water solution.

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 NaCl. a nonpolar solvent, such as hexane (C6H14) dissolves nonpolar solutes, such as oil or grease.

Like Dissolves Like Solvents Solutes Water (polar) Ni(NO3)2 CH2Cl2 (nonpolar) (polar) I2 (nonpolar)

Learning Check Will each of the following solutes dissolve in water? Why or why not? A. Na2SO4 B. gasoline (nonpolar) C. I2 D. HCl

Solution Will each of the following solutes dissolve in water? Why or why not? A. Na2SO4 Yes, the solute is ionic. B. gasoline No, the solute is nonpolar. C. I2 No, the solute is nonpolar. D. HCl Yes, the solute is polar. Most polar and ionic solutes dissolve in water because water is a polar solvent.