Unit 3 Mixtures Solutions Chapter 14 Mixtures Two

Unit 3 Mixtures & Solutions (Chapter 14)

Mixtures Two types of mixtures: • Heterogeneous • Homogenous

Heterogeneous • A heterogeneous mixture is a mixture that does not have a uniform composition and in which the individual substances remain distinct. Sulfur and Iron mixture.

Suspension • Suspensions are mixtures containing particles that settle out if left undisturbed. Examples: muddy water in a beaker, the mud will settle out and can than be physically filtered Large particle size (100 nm and larger)

Colloids • Colloids are heterogeneous mixtures of intermediate sized particles (between 1 nm & 100 nm) and do not settle out. The most abundant substance in a mixture is the dispersion medium. Colloids are categorized according to the phases of their particles.

Types of Colloids Pg 477

Brownian motion • Brownian motion is the jerky, random movements of particles in a liquid colloid, from the results of particle collisions.

Tyndall effect • The Tyndall effect is when dispersed colloid particles scatter light.

Homogeneous Mixtures Homogeneous mixtures are called “solutions”. There are two components to a solution. The solvent – which does the dissolving, and the solute which gets dissolved. In a solution the solvent and solute are indistinguishable if you look at it. Particle size of a solution is 0. 1 – 1. 0 nm. Does not exhibit the Tyndall effect. Can’t be separated by physical means (filter)

Pg. 479

Forming Solutions Soluble – a substance that dissolves in a solvent. Cu. Cl 2 and H 2 O Insoluble – will not dissolve in the solvent. Ag. Cl and H 2 O

Miscible – when two liquids are soluble in one another. Immiscible – two liquids that don’t mix well, and will separate upon standing.

Home Work Page 479, (2 5, & 8) Page 508 (54 -59)

Section 14. 2 Solution Concentration

The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution. Concentration can be described as concentrated or dilute.

• Molarity is the number of moles of solute dissolved per liter of solution.

Some Examples What is the molarity of a solution that has 3. 5 moles dissolved in 2. 0 L? M = #moles = L of soln. 3. 5 moles 2. 0 L M = 1. 75 M You need to put the unit of measurement after the number.

It’s not always that easy. You have 19. 5 g of Cu. Cl 2 dissolved in 750 m. L of water. What is the molarity of the solution? 1 st convert 19. 5 g into moles. 19. 5 g/134. 45 g = 0. 145 moles 2 nd convert 750 m. L to Liters. 750 m. L/1000 m. L = 0. 75 Liters Now M = #mol/L 0. 145 mol/ 0. 75 L = 0. 19 M Cu. Cl 2

Dilutions are when you take a concentrated solution and dilute it with distilled water. We can calculate the new molarity with this equation. Dilution equation: M 1 V 1 = M 2 V 2 M 1 is the concentrated molarity V 1 is the concentrated volume M 2 is the dilute molarity V 2 is the dilute volume

Example You have a bottle of 12 M HCl and you need to make 200 m. L of a 1. 0 M solution. The question is how much of the 12 M HCl will you need? We are looking for V 1 M 1 V 1 = M 2 V 2 rearrange V 1 = (M 2 X V 2) / M 1 V 1 = (1. 0 M x 200 m. L) / 12 M V 1 = 16. 67 m. L of the 12 M HCl 16. 67 m. L of the 12 M HCl and then you dilute it with distilled water up to 200 m. L in your beaker.

Section 14. 3 Factors Affecting Solvation

The Solvation Process Solvation is 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.

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

Solubility depends on the nature of the solute and solvent. Unsaturated solutions are solutions that contain less dissolved solute for a given temperature and pressure than a saturated solution.

Saturated solutions contain 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.

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.

Gases are less soluble in liquid solvents at high temperatures.

Section 14. 4 Colligative Properties of Solutions Colligative properties are physical properties of solutions that are affected by the number of particles but not by the identity of dissolved solute particles. • vapor pressure lowering • boiling point elevation • freezing point depression

Vapor Pressure Lowering Adding a nonvolatile solute 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.

Vapor pressure lowering is due to the number of solute particles in solution and is a colligative property of solutions

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. The temperature difference between a solution’s boiling point and a pure solvent's boiling point is called the boiling point elevation.

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.

Solute particles interfere with the attractive forces among solvent particles. A solution's freezing point depression is the difference in temperature between its freezing point and the freezing point of the pure solvent.