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Today:. Quiz Thursday / Friday May 16/17 HW – Read pages 257-258 Worksheet – Concentrations of solutions Worksheet - Molarity Problems 1. Molarity Problems 1. 0.0066 mol Na + ions 0.120 M KMnO 4 5.61 g (6 grams KMnO 4 ) 139 mL CaCl 2 0.44 g NaCl a) 207 g Ca 3 (PO 4 ) 2 b) Na 3 PO 4

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  1. Today: • Quiz Thursday / Friday May 16/17 • HW – Read pages 257-258 • Worksheet – Concentrations of solutions • Worksheet - Molarity Problems 1

  2. Molarity Problems 1 • 0.0066 mol Na+ ions • 0.120 M KMnO4 • 5.61 g (6 grams KMnO4) • 139 mL CaCl2 • 0.44 g NaCl • a) 207 g Ca3(PO4)2 b) Na3PO4 c) 0.0340M 7. 49.2 %

  3. Diluting a Stock Solution To make a solution LESS Concentrated: • Add solvent • Number of moles of solute does not change • Use formula: M1V1 = M2V2

  4. Molarity • Molarity = concentration term used to describe an amount of solute dissolved in a given amount of solution • Stock solution = concentrated solution. This contains large quantities of solute dissolved in solution • Dilute solution = contains small amounts of solute dissolved in solution

  5. Molarity • Take 2.00 grams of CuSO4 and dissolve it into 100. mL of water. • Calculate the molarity (M) of the stock solution. • 0.125 M CuSO4 = stock solution • How was the stock solution prepared?

  6. Preparation of Stock Solution • Weigh out 2.00 grams of copper(II) sulfate • Fill a 100. mL volumetric flask approximately ½ way with water. • Add in the solute (2.00 g) • Agitate until solute is completely dissolved. • Add water (solvent) until the solution reaches the line (score mark).

  7. Preparation of diluted solution • Take 3.00 mL of the stock solution and add it to a 25 mL volumetric flask; dilute to the line. • What is the molarity (M) of the diluted solution? • Use this formula: M1V1 = M2V2

  8. Dilution • M1 = 0.125 M • V1 = 3 mL • M2 = ? • V2 = 25 mL • M2 = 0.0150 M • How was the dilution prepared?

  9. Preparation of diluted solution • Take 3.00 mL of the stock solution using a volumetric pipette. • Add to a 25 mL volumetric flask. • Dilute with water until the solution reaches the line. • Mix the solution.

  10. Molarity and Dilution • 0.031 M • 5 Liters • 0.76 L 4.24 L evaporated 4. 102 grams By Monday – fish will die – you must come in! (0.0366 M) 5. a. Bert b. 0.164 M = Hank; 0.193 M = Bert c. 28 mL

  11. Molarity • M1V1 =M2V2 • Prepare 25 mL of 0.35M solution NaHCO3 from a stock solution which is 0.97M. How would you prepare the solution?

  12. Molality (m) • Concentration term that does not contain volume • Amount (mol) of solute / mass (kg) of solvent • SOLVENT not SOLUTION

  13. MOLALITY (molality) • What is the molality of a solution prepared by dissolving 32.0 g of CaCl2 in 217 g of water?

  14. Molarity and Dilution Problems Problem 6 • 94 moles • 5.5 L pure alcohol Problem 7 0.137 M Problem 8 • Weigh out 2205 grams of K2Cr2O7. Add it to a 5L volumetric flask that is ½ filled with water. Agitate to dissolve. Fill to the line with water. • Take 30. mL of stock solution using a volumetric pipette. Add it to a 450mL volumetric flask. Fill to the line with water. Shake.

  15. Molarity and Dilution Problems Problem 9 • 1.2 x 10-6 M • 2.08 x 10-6 grams

  16. Mass Percent • % (w/w) • Percent ratio as weights

  17. Mass Percent Mass percent = g solute x 100 (g solute + g solvent) Mass percent = g solute x 100 g solution

  18. Mass % What is the mass percent of sodium hydroxide in a solution that is made by dissolving 8.00 g NaOH in 50.0 g H2O?

  19. Mass % What masses of potassium chloride and water are needed to make 250. g of 5.00% solution?

  20. VOLUME PERCENT • % v/v • Percent volumes most often used for liquids and gases

  21. Concentration in Parts per volume • The label on a 0.750-L bottle of Italian chiante indicates “11.5% alcohol by volume.” How many liters of alcohol does the wine contain?

  22. % By Volume • What is the % by volume of ethanol (C2H6O) in the final solution when 75 mL of ethanol is diluted to a volume of 250 mL with water?

  23. Homework • Read Pages: 477-479 • WS: 17B Properties of solutions • Chapter 17 Practice Exam – For your review • Quiz Thurs/Fri May 27and 28 • Test June 7/8 Mon / Tuesday

  24. ppm (parts per million) Parts per million (ppm) = ppm = g solute x 1,000,000 g solution

  25. Concentration in parts by mass Find the concentration of calcium in parts per million (ppm) in a 3.50 g pill that contains 40.5 mg of Ca

  26. Mole Fraction (Χ) • Χ (chi) • Ratio of number of solute moles to the total number of moles (solute plus solvent)

  27. Mole Fraction • A sample of rubbing alcohol contains 142 g of isopropyl alcohol (C3H7OH) and 58.0 g of water. What are the mole fractions of alcohol and water?

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