Solution Notes Solution HW OBJECTIVES

HETEROGENEOUS MIXTURES Contain substances that exist in distinct phases. Two types are heterogeneous mixtures are suspensions and colloids. A. Suspensions A mixture containing particles that will settle out if left undissolved. Ex. sand and water. Can be separated by settling and/or filtration.

HETEROGENEOUS MIXTURES B. Colloids A heterogeneous mixture of intermediate size particles. Colloids are between a solution and a suspension. Ex. Milk, paint, jello. Brownian motion- erratic movement of colloid particles. Tyndall effect - scattering of light by colloid particles.

PROPERTIES OF SOLUTIONS, COLLOIDS, AND SUSPENSIONS Chapter 12

SOLUTIONS What are Solutions? (also called homogeneous mixtures) Mixture that is uniform and mixed to the molecular level

CHARACTERISTICS OF SOLUTIONS 1. solvent one doing the dissolving (greater portion) 2. solute one being dissolved (smaller portion) 3. soluble - solute can dissolve in solvent 4. insoluble - solute cannot dissolve in solvent 5. miscible - apply to liquids - can be mixed Ex. alcohol and water 6. immiscible - not able to mix Ex. oil and vinegar

NOT ALL SOLUTIONS ARE LIQUIDS

SOLVATION IN AQUEOUS SOLUTIONS 1. dissociation (separation of IONS) 2. solvation (surrounding solute particles by solvent particles) 3. hydration (special case of solvation, applying only to water) Something to remember about ionic compounds: Once an ionic compound dissociates, the free ions act independently of each other. So, a solution of sodium chloride acts like a solution of sodium ions and chloride ions; there is no such thing as "sodium chloride" in the solution.

MIXING VARIOUS OBJECTS Why are some substances soluble in one another whereas others are not? It has to do with polarity. Remember "like dissolves like“ 1. Polar solvent-polar solute ex. salt and water solvent pulls off solute and surrounds them due to strong attractive forces (solvation/hydration)

2 Polar solvent-nonpolar solute ex. wax in water or I2 in H2O solvent is not attracted to solute because of polarity difference 3. Nonpolar solvent-polar solute ex. salt in hexane (C6H14) no attraction

4. Nonpolar solvent-nonpolar solute ex. I2 in hexane weak intermolecular forces exist, but random molecular motion can eventually knock some particles loose.

SOLUBILITY 1. solubility - maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure 2. solution equilibrium (separation = rejoining) 3. saturated solution (undissolved substance in equilibrium with dissolved substance) 4. unsaturated solution (less than saturated amount of solute) 5. supersaturated solution (more solute than normal because was heated)

FACTORS THAT AFFECT RATE OF SOLVATION 1. Stirring - will increase dissolving 2. Increasing the surface area - will increase dissolving Ex. sugar cube dissolves slower than granular sugar 3. Temperature

FACTORS THAT AFFECT SOLUBILITY Temperature - See graph Solids Increase Gases Decrease

FACTORS THAT AFFECT SOLUBILITY Pressure The solubility of a gas in any solvent increases as its external pressure above the solution increases. Carbonated beverages depend on this fact

SOLUTION CONCENTRATION 1. Concentration- measure of how much solute is dissolved in a specific amount of solvent or solution 2. Dilute - a small amount of solute 3. Concentrated- a large amount of solute

© Houghton Mifflin Harcourt Publishing Company Molarity Molarity is the number of moles of solute in one liter of solution. For example, a “one molar” solution of sodium hydroxide contains one mole of NaOH in every liter of solution. The symbol for molarity is M. The concentration of a one molar NaOH solution is written 1 M NaOH. Chapter 12 Section 3 Concentration of Solutions

EXPRESSING CONCENTRATION Molarity (M) Most common unit of concentration Molarity (M) = moles of solute liters of solution Mols Molarity Liters

SAMPLE PROBLEMS Problem: 3 moles C6H12O6 in 100 ml equals what molarity? Problem: What is the molarity of a solution composed of 5.85 g of KI, dissolved in enough water to make L of solution?

DILUTING SOLUTIONS In the laboratory, you may use concentrated solutions of standard molarities called stock solutions. For example, concentrated hydrochloric acid (HC1) is 12M To dilute stock solutions you can use the following equation: M 1 V 1 =M 2 V 2 where M 1 and V 1 are the molarity and volume of the stock solution and M 2 and V 2 are the molarity and volume of the dilute solution

© Houghton Mifflin Harcourt Publishing Company Molality Molality is the concentration of a solution expressed in moles of solute per kilogram of solvent. A solution that contains 1 mol of solute dissolved in 1 kg of solvent is a “one molal” solution. The symbol for molality is m, and the concentration of this solution is written as 1 m NaOH. Chapter 12 Section 3 Concentration of Solutions

© Houghton Mifflin Harcourt Publishing Company The molality of any solution can be calculated by dividing the number of moles of solute by the number of kilograms of solvent: Chapter 12 Molality, continued Section 3 Concentration of Solutions

© Houghton Mifflin Harcourt Publishing Company Problem: What is the molality of 4.72 moles of KI in a 500. kg solution? Problem: What quantity, in grams, of methanol, CH3OH, is required to prepare a m solution in 400. g of water? Chapter 12 Sample Problems Section 3 Concentration of Solutions

ELECTROLYTES 1. Electrolyte - ionic compounds which dissociate in water to form solutions that conduct electricity 2. Strong electrolyte - one that produces many ions in solution Ex. NaCl > Na + + Cl- 3. Weak electrolyte- one that produces a few ions in solution 4. Nonelectrolyte - molecular compounds which dissolve in solution but do not conduct electricity Ex. sugar