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lecture over solutions, solubility, and colligative properties

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  1. 1. Solutions Test on Friday March 4
  2. 2. What is a solution ? <ul><li>A homogeneous mixture </li></ul><ul><li>Composed of a solute dissolved in a solvent </li></ul>Solute Solvent
  3. 3. How is a solution formed? <ul><li>Through the process of </li></ul><ul><li>Solute particles separate from each other and mix with the solvent </li></ul><ul><li>particles </li></ul><ul><li>Solvent particles </li></ul><ul><li>surround the solute </li></ul><ul><li>particles and pull </li></ul><ul><li>them away from other </li></ul><ul><li>solute particles </li></ul>solvation
  4. 4. Solute and Solvent <ul><li>Solvent </li></ul><ul><ul><li>Does the dissolving </li></ul></ul><ul><ul><li>Greater quantity (usually) </li></ul></ul><ul><li>Solute </li></ul><ul><ul><li>What is dissolved </li></ul></ul><ul><ul><li>Lesser quantity (usually) </li></ul></ul>
  5. 5. Like dissolves like <ul><li>Baking soda will dissolve in water, but not in oil…..why? </li></ul><ul><li>“ Like dissolves like” refers to the bonding and polarity of the particles in the solute and solvent </li></ul><ul><li>Polar means a substance </li></ul><ul><li>has a positive and a </li></ul><ul><li>negative end </li></ul><ul><li>Ionic compounds </li></ul>
  6. 6. Ionic compounds in solution Cl - Na + Cl - Na + Na + Cl - Cl -
  7. 7. Solubility <ul><li>Only a certain amount of solute can dissolve in a solvent under a certain set of conditions </li></ul><ul><li>When too much solute is added to a solution at that temperature, the excess solute will crystallize </li></ul><ul><li>and fall out of solution </li></ul><ul><li>Solubility is the maximum </li></ul><ul><li> amount of a solute that </li></ul><ul><li>dissolves in a solvent at </li></ul><ul><li>a given temperature </li></ul>
  8. 8. Saturation <ul><li>A saturated solution </li></ul><ul><ul><li>contains the maximum amount of dissolved solute </li></ul></ul><ul><ul><li>for a given amount of solvent </li></ul></ul><ul><ul><li>at a specific temperature and pressure </li></ul></ul>
  9. 9. Supersaturation <ul><li>A supersaturated solution </li></ul><ul><ul><li>contains more dissolved solute than a saturated solution </li></ul></ul><ul><ul><li>at the same temperature. </li></ul></ul>
  10. 10. Solubility Curves Shows how much solute will dissolve in 100 g of water at a certain temperature The line represents the saturated amount of solute Underneath the line represents an unsaturated amount Above the line represents a supersaturated amount
  11. 11. <ul><li>Which substance is most soluble at 40°C? </li></ul><ul><li>How many grams of NH 4 Cl will dissolve at 50°C? </li></ul><ul><li>What two substances have the same solubility at 24°C? </li></ul><ul><li>If you place 70 grams of KBr into 100g of water at 60°C, what </li></ul>type of solution have you made? <ul><li>How many grams of NaNO 3 will dissolve in 300.0g of water at </li></ul>10.0°C? NaNO 3 ~ 50 grams Yb 2 (SO 4 ) 3 KNO 3 unsaturated ~ 240 grams (80 x 3)
  12. 12. Increasing Solubility - Solids <ul><li>Increase the temperature </li></ul><ul><ul><li>Why? Increases the amount of solute-solvent collisions and increases speed and energy of particles </li></ul></ul><ul><li>Agitate the solution (stir) </li></ul><ul><ul><li>Why? Brings more </li></ul></ul><ul><ul><li>solvent particles closer to </li></ul></ul><ul><ul><li>the solute </li></ul></ul><ul><li>Decrease the particle size </li></ul><ul><ul><li>Increases the surface area </li></ul></ul><ul><ul><li>of the solute, making it </li></ul></ul><ul><ul><li>easier for solvent particles to </li></ul></ul><ul><ul><li>surround the solute </li></ul></ul>
  13. 13. Increasing Solubility – Gases <ul><li>Decrease the temperature </li></ul><ul><li>Increase the pressure </li></ul><ul><li>If you increase the pressure, </li></ul><ul><li>think of pressing the gas </li></ul><ul><li>particles into the liquid. </li></ul><ul><li>Increasing pressure always </li></ul><ul><li>increases the amount of </li></ul><ul><li>gas that can be dissolved </li></ul><ul><li>in a liquid. </li></ul>
  14. 14. Rate of Solvation <ul><li>Greater solubility = Faster solvation </li></ul><ul><li>The same factors that increase solubility, increase the rate of solvation </li></ul>
  15. 15. Concentration <ul><li>The larger the ratio of solute to solvent becomes, the more concentrated the solution is. </li></ul><ul><li>Concentrated – large ratio of solute to solvent </li></ul><ul><li>Dilute – small ratio of solute to solvent </li></ul>
  16. 16. Rates of Reaction <ul><li>Concentration affects the rate of reaction </li></ul><ul><li>Concentrated solutions react faster than dilute solutions </li></ul>
  17. 17. Molarity <ul><li>Most commonly used in chemistry </li></ul><ul><li>Abbreviated as M </li></ul><ul><li>Moles of solute in per liter of solution </li></ul>M = moles of solute Liters of solution
  18. 18. Electrolytes <ul><li>Electrolyte – ionic compound whose aqueous solution conducts an electric current </li></ul><ul><li>– electrolyte </li></ul><ul><li>– non-electrolyte </li></ul>NaCl Sugar How many moles of ions are produced by dissolving 1 mole of NaCl in water?
  19. 19. Colligative Properties <ul><li>Colligative - depending on the collection </li></ul><ul><li>Properties dependent on concentration , number of particles present </li></ul>
  20. 20. Boiling Point Elevation <ul><li>When vapor pressure equals atmospheric pressure, water boils </li></ul><ul><li>More particles = lower vapor pressure </li></ul><ul><li>Lower vapor pressure = higher boiling point </li></ul><ul><li>More particles = higher boiling point </li></ul>Which raises boiling point more, 1 mole of NaCl in water, or 1 mole of sugar in water?
  21. 21. Freezing Point Depression <ul><li>Solute particles interfere with attraction between solvent particles </li></ul><ul><li>More particles = lower freezing point </li></ul>
  22. 22. Osmosis <ul><li>Osmosis – diffusion of solvent across a semi-permeable barrier </li></ul><ul><li>Solvent goes from: </li></ul><ul><ul><li>Area of more solvent -> Area of less solvent </li></ul></ul>
  23. 23. Osmosis Semi-permeable barrier Pure Solvent Solution
  24. 24. Osmosis and Concentration <ul><li>Higher concentration = more osmotic pressure </li></ul>
  25. 25. Osmosis and you
  26. 26. Colligative Properties Review Atmosphere Vapor Pressure
  27. 27. Miscible and Immiscible <ul><li>Substances that are miscible will dissolve in each other. </li></ul><ul><ul><li>Example: alchohol and water </li></ul></ul><ul><li>Substances that are immiscible will mix but immediately separate. </li></ul><ul><ul><li>Example: oil and vinegar </li></ul></ul>