Lecture09221

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Lecture09221

  1. 1. Stoichiometry: Reactions in Solutions Lecture 9
  2. 2. What are they working with?
  3. 3. We cannot know the amount of a solute directly from its mass. We have to know its concentration before.
  4. 4. Solution consists of solute and solvent.
  5. 5. Concentration is the measure of how much of a given substance there is mixed with another substance.
  6. 6. Concentration is an intensive quality like density or temperature. It does not depend on the volume of the solution.
  7. 7. Molarity is the most important way of expressing concentration.
  8. 8. Molarity expresses the concentration in units of moles of solute per liter of solution: Molarity = moles of solute / liters of solution
  9. 9. A sample problem on calculating the molarity of a solution.
  10. 10. Molarity can be thought of as a conversion factor used to convert between volume of solution and amount of solute.
  11. 11. A sample problem on calculating mass of solute in a given volume of solution.
  12. 12. Procedure for Preparation of Molar Solutions: <ul><li>Weigh the solid needed. </li></ul><ul><li>Transfer the solid to a volumetric flask that contains about half the final volume of solvent. </li></ul><ul><li>Dissolve the solid thoroughly by swirling. </li></ul><ul><li>Add solvent until the solution reaches its final volume. </li></ul>
  13. 13. When a solution is diluted, only solvent is added.
  14. 14. A sample problem on preparing a dilute solution from a concentrated solution.
  15. 15. General approach for solving problems on reactions in solutions: <ul><li>Balance the equation. </li></ul><ul><li>Find the amount of one substance. </li></ul><ul><li>Relate it to the stoichiometrically equivalent amount of another substance. </li></ul><ul><li>Convert to the desired units. </li></ul>
  16. 16. A sample problem on calculating amounts of reactants and products for a reaction in solution.
  17. 17. A sample problem on solving limiting-reactant problems for reactions in solution.
  18. 18. THE END

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