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Chapter 14: Solutions

Chapter 14: Solutions. Ch. 14. Concentration formulas. Making a solution. Freezing pt. depression. Boiling pt. elevation. Concentration formulas. How do you make a solution?. Solvation : process of surrounding solute particles with solvent particles to form a solution

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Chapter 14: Solutions

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  1. Chapter 14: Solutions Ch. 14 Concentration formulas Making a solution Freezing pt. depression Boiling pt. elevation

  2. Concentration formulas

  3. How do you make a solution? • Solvation: process of surrounding solute particles with solvent particles to form a solution • Heat of solution: overall energy change that occurs during the solution formation process

  4. Speed of dissolving • Solution formation depends on how much solute will dissolve in solvent. Stir/agitate  Solute dissolves faster Increase temp  Solute dissolves faster Increase surface area  Solute dissolves faster

  5. Surface area

  6. Solubility – amount of solute that dissolvesin solvent at a given temp. and pressure

  7. Less solute than saturated solution Contains maximum amount of solute at given temp and pressure Contains more solute than it can theoretically hold at given temp. and pressure

  8. Factors affecting solubility Simulation: Solubility and temp

  9. Factors affecting solubility • Increase temp • increase solubility of solids • Allows supersaturated soln. to be made • decrease solubility of gases • Crystallization of supersaturated soln. initiated by • seed crystal • If container is scratched

  10. Factors affecting solubility

  11. Factors affecting solubility • Negligible for solubility of L and S • Increase pressure gas  increase solubility gas • (Henry’s Law)

  12. Section 2 Concentrations of Solutions Objective: Using Molarity (M)

  13. Change to moles!! 1. Mass of solute in grams 2. Amount of solute in mol 3. Volume of solute in L 4. Molar concentration, M

  14. 1. What is the molarity of a solution prepared by dissolving 37.94 g of potassium hydroxide in some water and then diluting the solution to a volume of 500.0 mL? Don’t forget to use moles! Given: Unknown:

  15. 2. Determine the molarity of a solution prepared by dissolving 141.6 g of citric acid, C3H5O(COOH)3 in water and then diluting the resulting solution to 3500.0 mL. Given: Unknown:

  16. 3. What is the molarity of a salt solution made by dissolving 280.0 mg of NaCl in 2.00 mL of water? Given: Unknown: mg… tricky? How do you get grams? Here’s a hint: 1g = 1000 mg

  17. 4. What is the molarity of a solution that contains 390.0 g of acetic acid, HC2H3O2, dissolved in enough acetone to make 1000.0 mL of solution? Given: Unknown:

  18. 5. An analytical chemist wants to make 750.0 mL of a 6.00 M solution of sodium hydroxide. What mass of NaOH will the chemist need to make this solution? Given: Unknown:

  19. 6. What mass of glucose, C6H12O6 would be required to prepare 5.000x103 L of a 0.215 M solution? Can you figure this out? Given: Unknown:

  20. 7. A solution has a volume of 2.0 L and contains 36.0 g of glucose (C6H12O6). If the molar mass of glucose is 180 g/mol. What is the molarity of the solution? Given: Unknown:

  21. 8. A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is its molarity? This is CAKE! Given: Unknown:

  22. Section 3: Colligative properties • Property that depends on amount of solute in solution, and not on identity of solution.

  23. Freezing point (FP) • Solute disrupts formation of orderly pattern; as a result, more kinetic energy must be withdrawn from a solution to cause solidification. * Solution that contains a solute has alower Freezing pointthan the pure solvent

  24. Boiling point (BP) • Since adding a solute to a solvent decreases VP, additional kinetic energy must be added to raise VP and initiate boiling. * Solution that contains a solute has ahigher boiling pointthan the pure solvent

  25. Factors affecting Colligative Properties • Increase amt. of solute, increase magnitude… • VP lowering • FP depression ~1 mol solute lowers FP by 1.86°C • BP elevation ~ 1 mole solute increases BP by 0.512°C

  26. Factors affecting Colligative Properties 2. Solutes that dissociate have greater effects than nondissociating (nonpolar) solutes 6 particles 9 particles 3 particles Affect colligative property least Affect colligative property most

  27. Calculations with Colligative properties • Freezing pt. depression (FP dep) • difference in temperature between FP of solution and FP of pure solvent ΔTf = (Kf)(m) FP dep. example problems

  28. FP dep example 1: What is the freezing point depression (ΔTf) of a 0.100 m solution made with water? ΔTf = (Kf)(m)

  29. FP dep. Example 2: A solution made with ethanol is made to lower the freezing point by 6.10˚C. What is the molality of the solution? ΔTf = (Kf)(m)

  30. Calculations with Colligative properties • Boiling point elevation (BP elev.) • difference in temp between BP of a solution and BP of pure solvent ΔTb = (Kb)(m) BP dep. example problems

  31. BP elev. Example 1: What molality of NaCl solution would have to be used raise the boiling point of water by 2.00˚C? ΔTb = (Kb)(m)

  32. BP elev. Example 2: Determine BP elevation (ΔTb) of a 0.857 m CaCl2 solution? ΔTb = (Kb)(m)

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