Mr. Kinton Honors Chemistry IMF’s and Solutions Mr. Kinton Honors Chemistry

Recall What do you remember about solids and their structure? What about liquids and their structure? Intra-particle forces: Ionic, Covalent, and Metallic bonds Classification of Matter:

Intermolecular Forces The forces that exist between molecules Weaker than Intra-particle forces Determine the properties of liquids such as boiling point Low boiling point=weaker IMF’s High boiling point=stronger IMF’s Same holds true for solids and their melting point

Types of Intermolecular Forces There are 3 types of intermolecular forces in neutral molecules: London-Dispersion forces Dipole-dipole forces Hydrogen Bonding The 3 are referred to as the van der Waals forces Each are electrostatic in nature

London Dispersion Forces Caused by electrons repelling one another Creates a temporary dipole Strongest in larger molecules Polarizability: the ability of an atoms electric field to be distorted Exist in all molecules

Dipole-Dipole Forces Positive end of one molecule is near the negative end of another molecule Only effective when polar molecules are near each other Dipole-Dipole forces occur between only polar molecules

Hydrogen Bonding Special type of attraction between a Hydrogen atom and either a F, O, or N atom of an adjacent molecule Causes higher than usual melting/boiling points Strongest intermolecular force

Ion-Dipole Force Attraction between an ion and a polar molecule Increases based on charge of the ion or the dipole moment Important in the formation of solutions

Melting/Boiling Points

IMF Flow Chart

Solution V. Colloid v. Suspension

Solutions Are they substances or mixtures? IMF’s interact between the solute and the solvent Solute: substance being dissolved Solvent: substance doing the dissolving

How do Solutions form Attractive forces between solute and solvent are comparable to the individual forces Solvation: when ions are separated and surrounded by a solvent Hydrations: solvation when water is the solvent This is a physical change

Energy Of Solution Formation

Energy Changes Exothermic Endothermic heat is released to the surroundings Spontaneous Feels warm heat is absorbed from the surroundings Can be spontaneous Feels cold

Entropy The amount of disorder in a system Processes that increase entropy tend to occur spontaneously Solution formation is favored when entropy increases

Solutions and Solubility Solubility: amount of solute needed to form a saturated solution in a solvent Saturated: solution that is in equilibrium with undissolved solute Unsaturated: less solute is dissolved than possible in a solution Supersaturated: occurs when a solution is heated, more solute is added, then cooled

Solubility Curves

Factors Affecting Solubility Solute-Solvent Interactions Pressure Effects Temperature Effects

Solute-Solvent Interactions Increase when there are stronger attractions between solute and solvent Hence “like dissolves like” Miscible: liquids that mix in all proportions Immiscible: liquids that do not dissolve each other

Pressure Effects Only impacts gases in solution Increasing pressure causes an increase in gas concentration

Temperature Effects Increase in temperature causes an increase in solid solubility Increase in temperature causes a decrease in gas solubility

Ways of Expressing Concentration Qualitatively quantitatively Dilute: relatively small concentration Concentrated: large concentration of solute Mass percentage Mole fraction Molarity Molality

Colligative Properties Properties that depend on the concentration of solute particles As the number of solute particles increase so do the colligative properties as well 4 Colligative Properties Vapor Pressure Boiling-Point Elevation Freezing-Point Depression Osmosis

Vapor Pressure Pressure exerted by a vapor in a closed container Nonvolatile: no measurable vapor pressure Volatile: has a measurable vapor pressure Adding a nonvolatile will lower the vapor pressure

Boiling Point Elevation/Freezing Point Depression Based on the presence of nonvolatile in the solution Adding a nonvolatile increases the boiling point, but lowers the freezing point Adding an electrolyte increases the effect

Osmosis Net movement of solvent toward a solution with higher concentration Stops when the osmotic pressure can stop the movement of the solvent