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End Show © Copyright Pearson Prentice Hall Slide 1 of 46 Concentrations of Solutions Water must be tested continually to ensure that the concentrations of contaminants do not exceed established limits. These contaminants include metals, pesticides, bacteria, and even the by- products of water treatment. You will learn how solution concentrations are calculated. (molarity; % v/v; %m/m; ppm) 16.2

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End Show Slide 2 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Molarity The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent. A dilute solution is one that contains a small amount of solute. A concentrated solution contains a large amount of solute. 16.2

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End Show © Copyright Pearson Prentice Hall Concentrations of Solutions > Slide 3 of 46 16.2 Molarity How do you calculate the molarity of a solution?

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End Show Slide 4 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Molarity Molarity (M) is the number of moles of solute dissolved in one liter of solution. To calculate the molarity of a solution, divide the moles of solute by the volume of the solution. 16.2

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End Show Slide 5 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Molarity To make a 0.5-molar (0.5M) solution, first add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water. 16.2

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End Show Slide 6 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Molarity Swirl the flask carefully to dissolve the solute. 16.2 Fill the flask with water exactly to the 1-L mark.

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16.2

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for Sample Problem 16.2

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16.3

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Sample Problem 16.3 16.3

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for Sample Problem 16.3

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End Show © Copyright Pearson Prentice Hall Slide 13 of 46 Concentrations of Solutions > 16.2 Making Dilutions What effect does dilution have on the total moles of solute in a solution? Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles of solute in solution does not change.

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End Show Slide 14 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions The total number of moles of solute remains unchanged upon dilution, so you can write this equation. M 1 and V 1 are the molarity and volume of the initial solution, and M 2 and V 2 are the molarity and volume of the diluted solution. 16.2

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End Show Slide 15 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions Making a Dilute Solution 16.2

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End Show Slide 16 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions To prepare 100 ml of 0.40M MgSO 4 from a stock solution of 2.0M MgSO 4, a student first measures 20 mL of the stock solution with a 20-mL pipet. 16.2

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End Show Slide 17 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions She then transfers the 20 mL to a 100-mL volumetric flask. 16.2

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End Show Slide 18 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions Finally she carefully adds water to the mark to make 100 mL of solution. 16.2

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End Show Slide 19 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Making Dilutions Volume-Measuring Devices 16.2

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16.4

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for Sample Problem 16.4

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End Show © Copyright Pearson Prentice Hall Slide 23 of 46 Concentrations of Solutions > Percent Solutions What are two ways to express the percent concentration of a solution? The concentration of a solution in percent can be expressed in two ways: as the ratio of the volume of the solute to the volume of the solution or as the ratio of the mass of the solute to the mass of the solution. 16.2

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End Show Slide 24 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Percent Solutions Concentration in Percent (Volume/Volume) 16.2

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End Show Slide 25 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Percent Solutions Isopropyl alcohol (2-propanol) is sold as a 91% solution. This solution consist of 91 mL of isopropyl alcohol mixed with enough water to make 100 mL of solution. 16.2

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16.5

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© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 27 of 46 End Show 16.5

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Practice Problems For Sample Problem 16.5 for Sample Problem 16.5

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End Show Slide 29 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Percent Solutions Concentration in percent (mass/mass) 16.2

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End Show Slide 30 of 46 © Copyright Pearson Prentice Hall Concentrations of Solutions > Parts per million Concentration in parts per million (ppm) (To complete) 16.2

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End Show © Copyright Pearson Prentice Hall Slide 31 of 46 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 16.2 Section Quiz. 16.1.

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© Copyright Pearson Prentice Hall Slide 32 of 46 End Show 16.2 Section Quiz. 1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in a.1.00 liter of water. b.enough water to make 1.00 liter of solution c.1.00 kg of water. d.100 mL of water.

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© Copyright Pearson Prentice Hall Slide 33 of 46 End Show 16.2 Section Quiz. 2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution? a.150 g b.75.0 g c.18.7 g d.0.50 g

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© Copyright Pearson Prentice Hall Slide 34 of 46 End Show 16.2 Section Quiz. 3. Diluting a solution does NOT change which of the following? a.concentration b.volume c.milliliters of solvent d.moles of solute

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© Copyright Pearson Prentice Hall Slide 35 of 46 End Show 16.2 Section Quiz. 4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is a.2000 g. b.100 g. c.1995 g. d.1900 g.

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© Copyright Pearson Prentice Hall Slide 36 of 46 End Show 16.2 Section Quiz. 4. In a 2000 g solution of glucose that is labeled 4.0 ppm, the mass of glucose is a.2000 g. b.100 g. c.1995 g. d.0.0080 g.

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