Chapter 12 Solutions 12.1 Solutions Learning Goal Identify the solute and solvent in a solution; describe the formation of a solution. © 2014 Pearson Education, Inc.

Calculating a Percentage (1.4C) Interpreting a Line Graph (1.4E) Chapter 12 Readiness Key Math Skills Calculating a Percentage (1.4C) Interpreting a Line Graph (1.4E) Core Chemistry Skills Writing Conversion Factors from Equalities (2.6) Using Conversion Factors (2.7) Identifying Attractive Forces (10.4) Using the Ideal Gas Law (11.8) © 2014 Pearson Education, Inc.

Solutions Solutions are homogeneous mixtures of two or more substances contain a solute, usually in smaller quantity, and uniformly dispersed in another substance called the solvent, usually present in greater quantity

Solutes Solutes are not visible and cannot be separated by filtration can be separated by evaporation can give color to a solution

Types of Solutes and Solvents The solutes and solvents in solutions can be solids, liquids, or gases.

Water as a Solvent Water, the most common solvent, is a polar molecule forms hydrogen bonds between molecules

Formation of a Solution Na+ and Cl ions on the surface of a NaCl crystal are attracted to polar water molecules in solution are hydrated by H2O molecules that surround each ion

Solute – Solvent Attractions Attractive forces occur between solute and solvent particles when the solute and solvent are similar in polarity. The expression “like dissolves like” describes the common polarities of the solute and solvent particles needed to form a solution.

Solute – Solvent Attractions Like dissolves like. In each test tube, the lower layer is Ch2Cl2 (more dense), and the upper layer is water (less dense). (a) Ch2Cl2 is nonpolar and water is polar; the two layers do not mix. (b) The nonpolar solute I2 (purple) is soluble in the nonpolar solvent Ch2Cl2. (c) The ionic solute Ni (No3)2 (green) is soluble in the polar solvent water.

Solute – Solvent Attractions

Solutions, Ionic Solutes In water, a polar solvent, the hydrogen bonds provide strong solvent–solvent attractions. When NaCl crystals are placed in water, partially negative oxygen atoms in water molecules attract positive Na+ ions partially positive hydrogen atoms in other water molecules attract negative Cl− ions

Solutions, Ionic Solutes When NaCl(s) dissolves in water, the formation of the solution can be written as NaCl(s) Na+(aq) + Cl−(aq) solid separation of ions H2O

Solutions, Polar Solutes Polar molecules such as CH3—OH are soluble because of the polar –OH group that forms hydrogen bonds with the polar solvent water.

Solutions, Nonpolar Solutes Solutes that are nonpolar, such as iodine (I2), oil, or grease, do not dissolve in the polar solvent water. There are no attractions between the nonpolar solute particles and the polar solvent. Nonpolar molecules will form a solution with nonpolar solvents.

Learning Check Solid LiCl is added to water. It dissolves because the Li+ ions are attracted to the 1) oxygen atom ( –) of water 2) hydrogen atom ( +) of water B. the Cl ions are attracted to the

Solution Solid LiCl is added to water. It dissolves because A. the Li+ ions are attracted to the 1) oxygen atom ( –) of water the Cl ions are attracted to the 2) hydrogen atom ( +) of water

Learning Check Will the following solutes dissolve in water? A. Na2SO4 B. gasoline (nonpolar) C. I2 D. HCl

Solution Will the following solutes dissolve in water? Na2SO4 Yes, the solute is ionic. gasoline (nonpolar) No, the solute is nonpolar. I2 No, the solute is nonpolar. HCl Yes, the solute is polar. Most polar and ionic solutes dissolve in water because water is a polar solvent.