Concentrations of solutions
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Concentrations of Solutions. 16.2.

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Concentrations of solutions

Concentrations of Solutions

16.2

  • 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)


Molarity

16.2

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.


Molarity1

16.2

Molarity

  • Molarity

    • How do you calculate the molarity of a solution?


Molarity2

16.2

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.


Molarity3

16.2

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.


Molarity4

16.2

Molarity

  • Swirl the flask carefully to dissolve the solute.

  • Fill the flask with water exactly to the 1-L mark.


Concentrations of solutions

16.2


Concentrations of solutions

16.2


Concentrations of solutions

for Sample Problem 16.2


Concentrations of solutions

16.3


Sample problem 16 3

16.3

Sample Problem 16.3


Concentrations of solutions

for Sample Problem 16.3


Making dilutions

16.2

Making Dilutions

  • 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.


Making dilutions1

16.2

Making Dilutions

  • The total number of moles of solute remains unchanged upon dilution, so you can write this equation.

  • M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the diluted solution.


Making dilutions2

16.2

Making Dilutions

  • Making a Dilute Solution


Making dilutions3

16.2

Making Dilutions

  • To prepare 100 ml of 0.40M MgSO4 from a stock solution of 2.0M MgSO4, a student first measures 20 mL of the stock solution with a 20-mL pipet.


Making dilutions4

16.2

Making Dilutions

  • She then transfers the 20 mL to a 100-mL volumetric flask.


Making dilutions5

16.2

Making Dilutions

  • Finally she carefully adds water to the mark to make 100 mL of solution.


Making dilutions6

16.2

Making Dilutions

  • Volume-Measuring Devices


Concentrations of solutions

16.4


Concentrations of solutions

16.4


Concentrations of solutions

for Sample Problem 16.4


Percent solutions

16.2

Percent 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.


Percent solutions1

16.2

Percent Solutions

  • Concentration in Percent (Volume/Volume)


Percent solutions2

16.2

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.


Concentrations of solutions

16.5


Concentrations of solutions

16.5


Practice problems for sample problem 16 5

for Sample Problem 16.5

Practice Problems For Sample Problem 16.5


Percent solutions3

16.2

Percent Solutions

  • Concentration in percent (mass/mass)


Parts per million

16.2

Parts per million

  • Concentration in parts per million (ppm)

  • (To complete)


16 2 section quiz

16.2 Section Quiz.

  • 16.1.


16 2 section quiz1

16.2 Section Quiz.

  • 1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in

    • 1.00 liter of water.

    • enough water to make 1.00 liter of solution

    • 1.00 kg of water.

    • 100 mL of water.


16 2 section quiz2

16.2 Section Quiz.

  • 2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution?

    • 150 g

    • 75.0 g

    • 18.7 g

    • 0.50 g


16 2 section quiz3

16.2 Section Quiz.

  • 3. Diluting a solution does NOT change which of the following?

    • concentration

    • volume

    • milliliters of solvent

    • moles of solute


16 2 section quiz4

16.2 Section Quiz.

  • 4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is

    • 2000 g.

    • 100 g.

    • 1995 g.

    • 1900 g.


16 2 section quiz5

16.2 Section Quiz.

  • 4. In a 2000 g solution of glucose that is labeled 4.0 ppm, the mass of glucose is

    • 2000 g.

    • 100 g.

    • 1995 g.

    • 0.0080 g.


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