Chapter 14: Mixtures and Solutions

CHEMISTRY Matter and Change Chapter 14: Mixtures and Solutions

Table Of Contents CHAPTER14 Section 14.1 Types of Mixtures Section 14.2 Solution Concentration Section 14.3 Factors Affecting Solvation Section 14.4 Colligative Properties of Solutions Click a hyperlink to view the corresponding slides. Exit

Review • Mixture vs. Compound • What are the differences???? • Are all mixtures solutions? • What are solutions??

Types of Mixtures SECTION14.1 Heterogeneous Mixtures A heterogeneous mixture is… • Suspensionsare mixtures containing particles that settle out if left undisturbed. Suspensions can also be separated by filtering. Examples: Thixotropic Mixture:

Types of Mixtures SECTION14.1 Heterogeneous Mixtures (cont.) • Colloids are heterogeneous mixtures of intermediate sized particles (between 1 nm and 1000 nm) and do not settle out, nor can they be filtered apart. • Examples: The most abundant substance in a mixture is the dispersion medium.

Types of Mixtures SECTION14.1 Heterogeneous Mixtures (cont.)

Types of Mixtures

Types of Mixtures SECTION14.1 Heterogeneous Mixtures (cont.) Brownian motion is the jerky, random movements of particles in a liquid colloid, from the results of particle collisions. The Tyndall effectis the scattering of light by dispersed colloid particles.

Types of Mixtures Lucretius (60 BC) wrote a poem describing a phenomenon that was remarkably similar to Brownian Motion: “Observe what happens when sunbeams are admitted into a building and shed light on its shadowy places. You will see a multitude of tiny particles mingling in a multitude of ways…their dancing is an actual indication of underlying movements of matter that are hidden from our sight.”

Types of Mixtures SECTION14.1 Homogeneous Mixtures Solutions are homogeneous mixtures that contain two or more substances called the solute and solvent. Solute = Solvent = Most solutions are liquids, but gaseous and solid solutions exist.

Types of Mixtures

Types of Mixtures SECTION14.1 Homogeneous Mixtures (cont.)

Types of Mixtures SECTION14.1 Homogeneous Mixtures (cont.) A substance that dissolves in a solvent is… Two liquids that are soluble in each other in any proportion are miscible. A substance that does not dissolve in a solvent is ____________ or a ____________ Two liquids that can be mixed but separate shortly after are immiscible.

Particle Model Assessment • I would like you to draw three beakers containing three different mixtures. In one beaker you should illustrate a suspension on the macroscopic scale. In another beaker illustrate a colloid, and finally in the third beaker illustrate a solution. • I want you to do the exact same thing as above, but now do it for the microscopic scale.

Solution Concentration SECTION14.2 Expressing Concentration The concentrationof a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution. Concentration can be described using one of the following terms: 1. 2.

Solution Concentration

Solution Concentration SECTION14.2 Expressing Concentration (cont.)

Solution Concentration • In order to maintain a sodium chloride concentration similar to ocean water, an aquarium must contain 3.6 grams NaCl per 100.0 grams of water. What is the percent by mass of NaCl in the solution?

Solution Concentration • What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 155 mL of water? • What is the percent by volume of isopropyl alcohol in a solution that contains 24 mL of isopropyl alcohol in 1.1 L of water?

Solution Concentration SECTION14.2 Expressing Concentration (cont.) Molarityis the number of moles of solute dissolved per liter of solution. Dilution equation: M1V1 = M2V2

Solution Concentration • A 100.5 mL IV solution contains 5.10 grams of glucose. What is the molarity of this solution? • What is the molarity of 1.60 L of a solution containing 1.55 grams of dissolved Potassium Bromide?

Solution Concentration Preparing Molar Solutions: • How many grams of calcium chloride would be dissolved in 1.0 L of a 0.10M solution of calcium chloride? • What mass of NaOH is in 250 mL of a 3.0M NaOH solution?

Solution Concentration Dilution Calculations • What volume, in milliliters, of 2.00M calcium chloride stock solution would you use to make 0.50 L of 0.300M calcium chloride solution? • How many mLs of a 5.0M sulfuric acid stock solution would you need to prepare 100.0 mL of 0.25M sulfuric acid solution? • **If 0.50L of 5.00M stock solution of HCl is diluted to make 2.0 L of solution, how much HCl, in grams, is in the solution?

Solution Concentration SECTION14.2 Expressing Concentration (cont.) Molalityis the ratio of moles of solute dissolved in 1 kg of solvent.

Solution Concentration • A student adds 4.5 grams of sodium chloride to 100.0 grams of water. Calculate the molality. • What is the molality of a solution containing 10.0 grams of sodium sulfate dissolved in 1000.0 grams of water?

Solution Concentration SECTION14.2 Expressing Concentration (cont.) Mole fractionis the ratio of the number of moles of solute in solution to the total number of moles of solute and solvent.

Solution Concentration SECTION14.2 Expressing Concentration (cont.) Percentage by moles

Factors Affecting Solvation SECTION14.3 The Solvation Process Why are some particles soluble in each other, while others are not? Solvationis the process of surrounding solute particles with solvent particles to form a solution. Solvation in water is called hydration. The attraction between dipoles of a water molecule and the ions of a crystal are greater than the attraction among ions of a crystal.

Factors Affecting Solvation SECTION14.3 The Solvation Process (cont.)

Factors Affecting Solvation SECTION14.3 The Solvation Process (cont.) Sucrose molecules have several O–H bonds, which become sites for hydrogen bonding with water molecules. Oil does not form a solution with water because there is little attraction between polar water molecules and nonpolar oil molecules.

Factors Affecting Solvation SECTION14.3 The Solvation Process (cont.) During solvation, the solute must separate into particles and move apart, which requires energy. The overall energy change that occurs during solution formation is called the heat of solution.

Factors Affecting Solvation SECTION14.3 Factors That Affect Solvation Stirring or shaking moves dissolved particles away from the contact surfaces more quickly and allows new collisions to occur thereby increasing the rate of solvation. Breaking the solute into small pieces increases surface area and allows more collisions to occur thereby increasing the rate of solvation. As temperature increases, rate of solvation increases.

Factors Affecting Solvation SECTION14.3 Solubility Solubility depends on the nature of the solute and solvent. Unsaturated solutionsare solutions that contain less dissolved solute for a given temperature and pressure than a saturated solution.

Factors Affecting Solvation SECTION14.3 Solubility (cont.) Saturated solutionscontain the maximum amount of dissolved solute for a given amount of solute at a specific temperature and pressure. Solubility is affected by increasing the temperature of the solvent because the kinetic energy of the particles increases.

Factors Affecting Solvation SECTION14.3 Solubility (cont.)

Factors Affecting Solvation SECTION14.3 Solubility (cont.) A supersaturated solution contains more dissolved solute than a saturated solution at the same temperature. To form a supersaturated solution, a saturated solution is formed at high temperature and then slowly cooled. Supersaturated solutions are unstable.

Factors Affecting Solvation SECTION14.3 Solubility (cont.) Gases are less soluble in liquid solvents at high temperatures. Solubility of gases increases as its external pressure is increased. Henry’s lawstates that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P).

Henry’s Law • If 0.85 grams of a gas at 4.0 atm of pressure dissolves in 1.0 L of water at 25 degrees Celsius, how much will dissolve in 1.0 L of water at 1.0 atm of pressure and the same temperature?

Colligative Properties of Solutions SECTION14.4 Electrolytes and Colligative Properties • Colligative propertiesare physical properties of solutions that are affected by the number of particles but not by the identity of dissolved solute particles. • Colligative means depending on the collection • Colligative properties include: vapor pressure lowering, boiling point elevation, freezing point depression and osmotic pressure.

Colligative Properties of Solutions SECTION14.4 Electrolytes and Colligative Properties (cont.) • Ionic compounds are electrolytes because they dissociate in water to form a solution that conducts electricity. • Electrolytes that produce many ions are strong electrolytes. • Electrolytes that produce only a few ions are weak electrolytes. • Many molecular compounds do not ionize when dissolved, and do not conduct electricity, these are called nonelectrolytes. • There are some exceptions, so those molecular compounds that do ionize are electrolytes.

Colligative Properties of Solutions SECTION14.4 Vapor Pressure Lowering Adding a nonvolatile solute (one that has little tendency to become a gas) to a solvent lowers the solvent’s vapor pressure. When a solute is present, a mixture of solvent and solute occupies the surface area, and fewer particles enter the gaseous state. The greater the number of solute particles, the lower the vapor pressure.

Colligative Properties of Solutions SECTION14.4 Vapor Pressure Lowering (cont.) Vapor pressure lowering is due to the number of solute particles in solution and is a colligative property of solutions.

Colligative Properties of Solutions SECTION14.4 Boiling Point Elevation When a nonvolatile solute lowers the vapor pressure of a solvent, the boiling point is also affected. More heat is needed to supply additional kinetic energy to raise the vapor pressure to atmospheric pressure.

Colligative Properties of Solutions SECTION14.4 Boiling Point Elevation (cont.) The temperature difference between a solution’s boiling point and a pure solvent's boiling point is called the boiling point elevation.

Colligative Properties of Solutions SECTION14.4 Boiling Point Elevation (cont.)

Colligative Properties of Solutions SECTION14.4 Freezing Point Depression At a solvent's freezing point temperature, particles no longer have sufficient kinetic energy to overcome interparticle attractive forces. The freezing point of a solution is always lower than that of the pure solvent.

Colligative Properties of Solutions SECTION14.4 Freezing Point Depression (cont.) Solute particles interfere with the attractive forces among solvent particles. A solution's freezing point depressionis the difference in temperature between its freezing point and the freezing point of the pure solvent.

Colligative Properties of Solutions SECTION14.4 Freezing Point Depression (cont.)

Colligative Properties of Solutions SECTION14.4 Osmotic Pressure Osmosis is the diffusion of a solvent through a semipermeable membrane.

Colligative Properties of Solutions SECTION14.4 Osmotic Pressure (cont.) Osmotic pressureis the amount of additional pressure caused by water molecules that moved into the concentrated solution.

Chapter 14: Mixtures and Solutions