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Chemistry 16.4. Calculations Involving Colligative Properties. 16.4. - PowerPoint PPT Presentation
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Chemistry 16.4
© Copyright Pearson Prentice Hall
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Calculations Involving Colligative Properties
Cooking instructions often call for the addition of a small amount of salt to the cooking water. Dissolved salt elevates the boiling point of water. You will learn how to calculate the amount the boiling point of the cooking water rises.
16.4
© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
>
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16.4 Molality and Mole Fraction
Molality and Mole Fraction
What are two ways of expressing the concentration of a solution?
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Calculations Involving Colligative Properties
> Molality and Mole Fraction
The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution.
16.4
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Molality and Mole Fraction
The unit molality (m) is the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent. Molality is also known as molal concentration.
16.4
Slide 6 of 42
© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Molality and Mole Fraction
To make a 0.500m solution of NaCl, use a balance to measure 1.000 kg of water and add 0.500 mol (29.3 g) of NaCl.
16.4
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Molality and Mole Fraction
Ethlylene Glycol (EG) is added to water as antifreeze.
16.4
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SAMPLE PROBLEM
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16.6
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SAMPLE PROBLEM
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16.6
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM
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16.6
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM
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16.6
© Copyright Pearson Prentice Hall
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Practice Problems
Practice ProblemsFor Sample Problem 16.6
Problem Solving 16.29 Solve Problem 29 with the help of an interactive guided tutorial.
for Sample Problem 16.6
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Molality and Mole Fraction
The mole fraction of a solute in a solution is the ratio of the moles of that solute to the total number of moles of solvent and solute.
16.4
Slide 14 of 42
© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Molality and Mole Fraction
In a solution containing nA mol of solute A and nB mol of solvent B (XB), the mole fraction of solute A (XA) and the mole fraction of solvent B (XB) can be expressed as follows.
16.4
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SAMPLE PROBLEM
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16.7
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SAMPLE PROBLEM
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16.7
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SAMPLE PROBLEM
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16.7
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SAMPLE PROBLEM
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Sample Problem 16.7
16.7
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Practice Problems
Problem Solving 16.32 Solve Problem 32 with the help of an interactive guided tutorial.
for Practice Problem 16.7
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
Freezing-Point Depression and Boiling-Point Elevation
How are freezing-point depression and boiling-point elevation related to molality?
16.4
© Copyright Pearson Prentice Hall
Slide 21 of 42
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
The magnitudes of the freezing-point depression and the boiling-point elevation of a solution are directly proportional to the molal concentration (m), when the solute is molecular, not ionic.
16.4
Slide 22 of 42
© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
The constant, Kf, is the molal freezing-point depression constant, which is equal to the change in freezing point for a 1-molal solution of a nonvolatile molecular solute.
16.4
Slide 23 of 42
© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
16.4
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
The constant, Kb, is the molal boiling-point elevation constant, which is equal to the change in boiling point for a 1-molal solution of a nonvolatile molecular solute.
16.4
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
16.4
© Copyright Pearson Prentice Hall
Slide 26 of 42
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
Simulation 21 Discover the principle underlying the colligative properties of solutions.
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© Copyright Pearson Prentice Hall
Calculations Involving Colligative Properties
> Freezing-Point Depression and Boiling-Point Elevation
16.4
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SAMPLE PROBLEM
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16.8
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SAMPLE PROBLEM
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16.8
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM
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16.8
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM
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16.8
© Copyright Pearson Prentice Hall
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Practice Problems
Problem Solving 16.33 Solve Problem 33 with the help of an interactive guided tutorial.
for Sample Problem 16.8
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SAMPLE PROBLEM
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16.9
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SAMPLE PROBLEM
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16.9
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SAMPLE PROBLEM
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16.9
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SAMPLE PROBLEM
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16.9
© Copyright Pearson Prentice Hall
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Practice Problems
Problem Solving 16.36 Solve Problem 36 with the help of an interactive guided tutorial.
for Sample Problem 16.9
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Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
16.4 Section Quiz.
16.4.
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Slide 39 of 42
16.4 Section Quiz.
1. What is the mole fraction of He in a gaseous solution containing 4.0 g of He, 6.5 g of Ar, and 10.0 g of Ne?
a. 0.60
b. 1.5
c. 0.20
d. 0.11
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16.4 Section Quiz.
2. The freezing point depression caused by a given concentration of a nonvolatile molecular solute
a. depends on the solute.
b. depends on the solvent.
c. is always the same.
d. cannot be determined.
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Slide 41 of 42
16.4 Section Quiz.
3. What are the freezing and boiling points of a 0.1m solution of CaCl2 in water?
a. -0.2°C, 100.1°C
b. -0.6°C, 100.1°C
c. -0.6°C, 100.2°C
d. -0.6°C, 99.8°C
© Copyright Pearson Prentice Hall
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16.4 Section Quiz.
4. Compared to the freezing point depression by ethylene glycol (C2H6O2,) for a given solvent, the freezing point depression caused by the same molal concentration of CaCl2 would be
a. exactly the same.
b. twice as large.
c. three times as large.
d. four times as large
END OF SHOW
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