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Solutions

Brass = solution. Coffee = solution. Solutions. Chapter 15. Jayhawk says: Chemistry is awesome! Go KU!. The Triple “S” – solution, solvent, solute. Solution: a homogeneous mixture in which the components are uniformly intermingled.

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Solutions

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  1. Brass = solution Coffee = solution Solutions Chapter 15 Jayhawk says: Chemistry is awesome! Go KU!

  2. The Triple “S” – solution, solvent, solute • Solution: a homogeneous mixture in which the components are uniformly intermingled. • Solvent: the dissolving medium; substance present in the largest amount • Solute: substance dissolved in a solvent Jayhawk says: Did you know solutions with water as the solvent are Aqueous solutions? Solute + Solvent

  3. The Triple “S” – solution, solvent, solute • When a solid is being dissolved in a liquid to form a solution, three factors affect the speed of the dissolving process; Surface area, stirring and temperature. Jayhawk says: Did you know that the Jayhawks were the National Champions in basketball in 2008? Solute + Solvent

  4. Solubility • Solids • Gases

  5. The most commonly used expression of concentration is molarity. Molarity Jayhawksays: Rock Chalk Jayhawk!! Go KU!!

  6. M = moles of solute liter of solution Examples: #1) A solution contains 0.90 mol of NaCl in 0.50 L of water. Calculate the M of this solution. 0.90 mol NaCl = 1.8 M 0.50 L H2O Molarity Jayhawksays: Remember to convert to liters if given milliliters. #2) A solution contains 1.2 g of Magnesium chloride in 100 mL of Water. Calculate the M.

  7. Answer: 1.2g MgCl2 x 1 mol MgCl2 = 0.013mol MgCl2 93.2 g MgCl2 0.013 mol MgCl2= 0.13 M 0.100 L H2O Molarity Jayhawksays: Remember significant figure rules.

  8. Another Example!! A 0.40 M solution of glucose contains 8 moles of the solute. What is the volume of this solution? Molarity Jayhawksays: Chemistry RULES!!

  9. Answer: Molarity = mol solute L of soln So, L (volume) of soln = mol solute Molarity Molarity L = 8 mol 0.40 M Jayhawksays: Remember significant figure rules. Volume = 20 L

  10. Molality is the number of moles of a given substance per kilogram of solvent. • m = Moles of solute • Kg of Solvent • "one molal solution", i.e. a solution which contains one • mole of the solute per 1000 grams of the solvent. Molality Jayhawksays: Chemistry is my favorite class!!

  11. A solution is prepared by dissolving 0.500 mol of NaCl in 1.000 Kg of H20. Calculate the molality. A solution contains 1.5 mol of NaCl in 100. g of H20. Calculate the molality. Molality Jayhawksays: Who did the Jayhawks beat in the Orange Bowl last year?

  12. How many g of potassium iodide must be dissolved in 500. g of water to give a 0.060 molal solution? Molality Jayhawksays: You need to know molality so we can make ice cream.

  13. Mole Fraction • Ratio of the number of moles of solute to number of moles of solute and solvent (solution)

  14. To concentrate a solution, one must add more solute, or reduce the amount of solvent (for instance, by selective evaporation). • By contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. • The # of moles of solute stays constant. More H20 is added which increases the volume while decreasing the Molarity. Dilution Light, and able to see through, (lightly concentrated)

  15. Dilution Equation: • M(1)V(1) = M(2)V(2) • M(1)V(1) are the initial conditions • M(2)V(2) are the final conditions (dilute) Dilution

  16. How would you prepare 100 mL of 0.40 M MgSO4 from a stock solution of 2.0 M MgSO4? Dilution

  17. You have 1000 mL of 1.0 M HCl in your stockroom. You need 15 mL of 0.02 M solution for a lab. How much of the original solution will you need to make this solution? Dilution

  18. Dilution Equation: • M(1)V(1) = M(2)V(2) • M(1)V(1) are the initial conditions • M(2)V(2) are the final conditions (dilute) Dilution

  19. Definitions to Know • Saturated Solution • Unsaturated Solution • Supersaturated Solution Jayhawk says: I hope you learned something in this chapter, and remember, Rock Chalk Jayhawk!

  20. Percent Volume - volume of solute x 100 volume of soln - used for liquids dissolved within liquids Calculate the % V of isoprpopanol when 20. mL of the alcohol Is diluted with water for a final volume of 100. mL A soln has a total V of 1000 mL after water was added to 25 mL of ethanol. What is the % V of the ethanol soln? Jayhawk says: Listen up class, it’s time for an example.

  21. Mass Percent • mass of solute x 100 • mass of soln • grams of solution = grams of solute + grams of solvent A hydrochloric acid soln was made by adding 59.26 g of HCl to 100 g H20. Calculate the % mass of HCl in the soln. Calculate the mass % of octane when 10.5 g C8H18 is mixed with 40.0 g of C6H14.Octane is the solute. Jayhawk says: How many more days of school do we have? Answer on next page.

  22. Percent Mass/ Volume • mass of solute x 100 • volume of soln • most often seen with g/mL units, but g/L are o.k. (make sure to label) A 100 mL soln containing 7.0 g of MgCl2 is what % mass/volume of MgCl2? Jayhawk says: 45, After today!! Yippee!!

  23. Solution Composition • Calculating ion concentration from Molarity • Solute concentration is always written in terms of the solute form before it dissolves. • Now, we need to account for ions in soln, dissociation of ions when dissolved. Jayhawk says: What is in that beaker of magnesium chloride solution?

  24. Solution Composition • Needed • Solubility Tables • Balanced Equations • Net Ionic Equations • M = [ ] Jayhawk says: Don’t forget to always check your solubility table!

  25. Give the [ ] of all ions in the soln below • 0.50 M Co(NO3)2 • Dissociation Rxn: • Determine M of each ion:

  26. Give the [ ] of all ions in the soln below • 1.0 M FeCl3 • Dissociation Rxn: • Determine M of each ion:

  27. How many moles of Ag+ ions are present in 25 mL of a 0.75 M AgNO3 soln? • Unk: • Given: • Dissoc. Rxn:

  28. Solution Stoichiometry • Incorporating Stoichiometry, road maps, with new soln. info. • Use M, molarity: mol , L as a conversion factor between moles and Liters • L mol • Never use 22.4 L . This is for gases only!! • mol • Many types of problems . . . • Always start by writing a balanced equation • Make a road map • Write givens and unknown Jayhawk says: 22.4 L is for gases only!!

  29. Solution Stoichiometry 1.0 L of 0.120 M calcium nitrate reacts with 3.0 L 0.050 M sodium chromate. What mass of the precipitate will form? • Rxn: • Net Ionic: • Road Map: • Stoich: Jayhawk says: This is a limiting reactant problem. Remember those?!!

  30. Solution Stoichiometry What volume of 2.50 M soln of silver nitrate is needed to completely precipitate out 4.2 g of silver chloride? • Rxn: • Net Ionic: • Road Map: • Stoich: Jayhawk says: Don’t Forget, TEST Next Class!!

  31. Solution Stoichiometry Ammonium phosphate and calcium chloride react. 0.15 g of the ppt forms from excess (NH4)3PO4 and 416 mL of a CaCl2 soln. What must have been the [ ], in M of the CaCl2 soln? • Rxn: • Net Ionic: • Road Map: • Stoich: Jayhawk says: Study, Study, Study!!

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