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

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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 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 %

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

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

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?

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).

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

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?

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.

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

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?

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

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

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.

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

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

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

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?

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

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

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?

% 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?

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

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

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

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

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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