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

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Molarity Problems 1 1. 0.0066 mol Na + ions 2. 0.120 M KMnO 4 3. 5.61 g (6 grams KMnO 4 ) 4. 139 mL CaCl 2 5. 0.44 g NaCl 6. a) 207 g Ca 3 (PO 4 ) 2 b) Na 3 PO 4 c) 0.0340M 7. 49.2 %

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Diluting a Stock Solution To make a solution LESS Concentrated: Add solvent Number of moles of solute does not change Use formula: M 1 V 1 = M 2 V 2

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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

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Molarity Take 2.00 grams of CuSO 4 and dissolve it into 100. mL of water. Calculate the molarity (M) of the stock solution. 0.125 M CuSO 4 = stock solution How was the stock solution prepared?

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Preparation of Stock Solution 1. Weigh out 2.00 grams of copper(II) sulfate 2. Fill a 100. mL volumetric flask approximately ½ way with water. 3. Add in the solute (2.00 g) 4. Agitate until solute is completely dissolved. 5. Add water (solvent) until the solution reaches the line (score mark).

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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: M 1 V 1 = M 2 V 2

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Dilution M 1 = 0.125 M V 1 = 3 mL M 2 = ? V 2 = 25 mL M 2 = 0.0150 M How was the dilution prepared?

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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.

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Molarity and Dilution 1. 0.031 M 2. 5 Liters 3. 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

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Molarity M 1 V 1 = M 2 V 2 Prepare 25 mL of 0.35M solution NaHCO 3 from a stock solution which is 0.97M. How would you prepare the solution?

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

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MOLALITY (molality) What is the molality of a solution prepared by dissolving 32.0 g of CaCl 2 in 217 g of water?

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Molarity and Dilution Problems Problem 6 a. 94 moles b. 5.5 L pure alcohol Problem 7 0.137 M Problem 8 a. Weigh out 2205 grams of K 2 Cr 2 O 7. Add it to a 5L volumetric flask that is ½ filled with water. Agitate to dissolve. Fill to the line with water. b. Take 30. mL of stock solution using a volumetric pipette. Add it to a 450mL volumetric flask. Fill to the line with water. Shake.

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Molarity and Dilution Problems Problem 9 a. 1.2 x 10 -6 M b. 2.08 x 10 -6 grams

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Mass Percent % (w/w) Percent ratio as weights

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Mass Percent Mass percent = g solutex 100 (g solute + g solvent) Mass percent = g solutex 100 g solution

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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 H 2 O?

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

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

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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?

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% By Volume What is the % by volume of ethanol (C 2 H 6 O) in the final solution when 75 mL of ethanol is diluted to a volume of 250 mL with water?

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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

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ppm (parts per million) Parts per million (ppm) = ppm= g solutex 1,000,000 g solution

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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

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

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Mole Fraction A sample of rubbing alcohol contains 142 g of isopropyl alcohol (C 3 H 7 OH) and 58.0 g of water. What are the mole fractions of alcohol and water?

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