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IMF’s and Solutions

Learn about the structure of solids and liquids, as well as the different types of intermolecular forces. Explore how these forces determine the properties of substances and the formation of solutions. Discover the effects of solute-solvent interactions, pressure, and temperature on solubility, and understand the concept of concentration and colligative properties.

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IMF’s and Solutions

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

  2. 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:

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. Melting/Boiling Points

  10. IMF Flow Chart

  11. Solution V. Colloid v. Suspension

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

  13. 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

  14. Energy Of Solution Formation

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

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

  17. 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

  18. Solubility Curves

  19. Factors Affecting Solubility • Solute-Solvent Interactions • Pressure Effects • Temperature Effects

  20. 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

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

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

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

  24. 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

  25. 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

  26. 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

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

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