Complete Test Bank Chapter.9 Properties Of Solutions 407

CHAPTER 9

PROPERTIES OF SOLUTIONS

CHAPTER STUDY OBJECTIVES

1. Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

SKILLS TO MASTER: Calculating concentrations in mass %, molarity, molality, mole fraction, ppm, and ppb; converting from one concentration unit to another

KEY CONCEPTS: The solvent determines the phase of the solution. Concentrations are expressed as amount of solute divided by the amount of solvent, or by the amount of solution.

2. Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

KEY CONCEPTS: Substances that dissolve in each other usually have similar types of intermolecular interactions (“like dissolves like”).

3. Calculate and explain solubilities in water.

SKILLS TO MASTER: Using Henry’s law to calculate gas solubility

KEY CONCEPTS: Enthalpies of solution and of dilution depend on the lattice energy of the salt as well as the hydration energies of its ions. The solubility of a gas in a liquid depends on the partial pressure of the gas.

4. Understand the reasons for and calculate the magnitudes of colligative properties.

SKILLS TO MASTER: Using Raoult’s law to calculate the vapour pressure of a solution; using Raoult’s law to calculate the composition of the products of distillation; calculating the boiling point elevation and freezing point depression due to the addition of a solute; calculating the osmotic pressure of a solution; using osmotic pressure to calculate the molar mass of a solute

KEY CONCEPTS: For a broad range of solutes, colligative properties depend on the amount of solute but not on the nature of the solute. Differences in vapour pressure can be used to separate liquid mixtures by fractional distillation. Boiling point elevation and freezing point depression result from a decrease in solution vapour pressure compared with the pure solvent.

5. Understand some aspects of colloidal suspensions and surfactant solutions.

KEY CONCEPTS: A colloidal suspension has properties intermediate between those of a true solution and those of a heterogeneous mixture. A surfactant molecule has a polar head group and a non-polar tail. Monolayers, micelles, and vesicles can form when surfactants are placed in water.

Multiple Choice QUESTIONS

1. What is the molarity of a solution made from mixing 34 grams of CaCl₂ with enough water to make 150 ml of solution?

a) 2.04 M

b) 1.02 M

c) 3.60 M

d) 0.20 M

e) 0.34 M

Difficulty: Easy

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

2. What is the molarity of an aqueous solution that is 0.569 m CaCl₂ (solution density 1.05 g/ml)?

a) 0.569 M

b) 0.562 M

c) 0.597 M

d) 0.507 M

e) 0.507 m

Difficulty: Hard

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

3. What is the mass percent of an aqueous solution that is 0.569 m CaCl₂ (solution density 1.05 g/ml)?

a) 5.94 %

b) 6.32 %

c) 0.06 %

d) 5.94 x 10^-2 %

e) 6.32 x10^-2%

Difficulty: Medium

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

4. What is the mole fraction of CaCl₂ in an aqueous solution that is 0.569 m CaCl₂ (solution density 1.05 g/ml)?

a) 0.01 M

b) 0.01

c) 0.57

d) 0.10

e) 9.6 x 10^-3

Difficulty: Easy

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

5. What is the molality of a radiator solution made by mixing equal volumes of ethylene glycol C₂H₆O₂, (density = 1.11 g/ml) and water?

a) 17.9 m

b) 11.1 m

c) 1.79 m

d) 4.60 m

e) 17.9 M

Difficulty: Medium

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

6. What is the molality of a solution made from mixing 39 grams of sugar (MM = 180 g/mol) with 310 grams of water?

a) 0.70 m

b) 1.40 m

c) 0.39 m

d) 3.10 m

e) 0.39 M

Difficulty: Easy

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

7. What is the mole fraction of ethyl alcohol (C₂H₆O, density = 0.79 g/ml) in water for a solution made from equal volumes of each?

a) 0.235

b) 0.122

c) 0.756

d) 1.11

e) 17.9

Difficulty: Medium

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

8. Why was the concentration unit of molality developed?

a) Molarity had not been developed yet.

b) Morality had not been developed yet.

c) Solution volumes changed with temperature.

d) Solution volumes changed with pressure.

e) Solution masses changed upon mixing.

Difficulty: Easy

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

9. The interactions that play an important role in the dissolution of a salt in water are

I. ion–dipole

II. hydrogen bonding

III. dipole-dipole

IV. ion–ion

a) I only

b) II and I

c) I and IV

d) II, III, and IV

e) I, II and IV

Difficulty: Hard

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

Feedback: Extent of dissolution is driven, in part, by the relative strengths of hydrogen bonding in water, the strength of the anion–cation bond and the strength of solvation (ion–dipole interaction) between the cations and water and the anions and water).

10. Benzene and water are immiscible, forming two separate layers when mixed. Samples of the compounds below are shaken in a mixture of benzene and water. Which of the following compounds would you expect to be found in the benzene layer?

a) 2 and 4

b) 2 and 3

c) 1 and 4

d) 1 and 3

e) 1, 3 and 4

Difficulty: Medium

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

11. List the following in order of solubility in hexane:

1) CH₃CH₂C(O)CH₃, 2) C₆H₆, 3) CH_­3CH₂CH₂CO₂H, 4) CH₃CH₂CH₂CH₂CO₂H

a) 2 < 1 < 3 < 4

b) 1 < 3 < 4 < 2

c) 3 < 4 < 1 < 2

d) 4 < 3 < 1 < 2

e) 1 < 2 < 3 < 4

Difficulty: Medium

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

12. How can mercury be used in dental fillings?

a) It is a solid at body temperature.

b) It forms an amalgam with your tooth enamel.

c) It forms an amalgam with other metals.

d) It is an insoluble salt in your mouth.

e) It forms a compound called brass with copper.

Difficulty: Easy

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

13. Which of the following statements regarding alloys is(are) true?

I. Alloys are homogeneous solid solutions

II. Alloys display metallic properties

III. The solute component in the alloy can replace the solvent component in the solid crystalline structure

IV. The solute component can be incorporated in between solvent atoms in the crystal structure

a) I only

b) II and I

c) I and IV

d) II, III, and IV

e) I, II and IV

Difficulty: Easy

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

Feedback: Must recognize that alloys may be homogenous or heterogeneous mixtures.

14. What is the concentration of chloride ions in a solution that is 0.569 m CaCl₂ (solution density 1.05 g/ml)?

a) 0.569 M

b) 0.562M

c) 1.124 M

d) 0.507 M

e) 1.138 M

Difficulty: Hard

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

Feedback: Student must recognize that ion concentration and salt concentration differ.

15. What is the concentration of all ions in a solution that is 0.569 m CaCl₂ (solution density 1.05 g/ml)?

a) 0.569 M

b) 0.562M

c) 1.124 M

d) 1.686 M

e) 2.248 M

Difficulty: Hard

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

Feedback: Student must recognize that ion concentration and salt concentration differ.

16. The greatest gas solubility for a gas in solution is predicted under what conditions?

a) low T, low P

b) low T, high P

c) high T, low P

d) high T, high P

e) Solubility of gases does not depend upon temperature.

Difficulty: Easy

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

17. Consider a warm (30°) 355 mL can of soda, under 2.5 atm CO₂ pressure. What volume of CO₂ will be released from the soda in order to reach equilibrium after opening to the room where the pressure of CO₂ = 3.25 x 10^-4 atm and the total pressure is 758 mm Hg (K_H = 1.6 x 10^-2 M/atm)?

a) 3.5 mL

b) 3.5 L

c) 35 mL

d) 0.35 L

e) 100 mL

Difficulty: Hard

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

18. According to Henry’s Law, the solubility of a gas in a liquid

a) depends on the polarity of the liquid.

b) depends on the liquid’s density.

c) remains the same at all temperatures.

d) increases as the gas pressure above the solution increases.

e) decreases as the gas pressure above the solution increases.

Difficulty: Easy

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

19. Carbon dioxide and O₂ are non-polar molecules. Can you provide some rational why CO_­2 dissolves so much more in water than O₂?

a) CO_­2 can hydrogen bond and O­₂ cannot.

b) CO₂ reacts with water and O₂ does not.

c) O₂ reacts with water and CO₂ does not.

d) CO₂ forms a solid with water.

e) Water decomposes to O₂.

Difficulty: Medium

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

20. Which of the following has the substances arranged in order of increasing heat of fusion?

a)

b)

c)

d)

e)

Difficulty: Medium

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

21. Which of the following statements regarding solubility as a function of temperature are correct?

I. Gas solubility favours high temperature and high pressure.

II. Gas solubility favours low temperature and high pressure.

III. Since the dissolution of solids into liquids is exothermic, solid solubility favours high temperature.

IV. Endothermic dissolution of solids in liquids is favoured by lower temperature.

V. Endothermic dissolution of solids in liquids is favoured by higher temperature.

a) I and V

b) II and IV

c) II and III

d) II and V

e) I and IV

Difficulty: Easy

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

22. The vapour pressure of toluene at 25^oC is 3.79 KPa and that of benzene is 12.7 kPa. The vapour above a solution that has mole fraction of benzene = 0.5,

a) has mole fraction toluene in 0.5.

b) has mole fraction of toluene less than 0.5.

c) has mole fraction of toluene greater than 0.5.

d) is pure benzene.

e) is pure toluene.

Difficulty: Easy

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

23. The boiling point of toluene is 110^oC and that of benzene is 80^oC. The vapour above a solution that has mole fraction of benzene = 0.5,

a) has mole fraction toluene in 0.5.

b) has mole fraction of toluene less than 0.5.

c) has mole fraction of toluene greater than 0.5.

d) is pure benzene.

e) is pure toluene.

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

24. Sea water has about 0.46 moles NaCl and 0.065 moles of MgCl_­2 in every litre. What is the vapour pressure of sea water at 30˚C if pure water would have a vapour pressure of 33.2 mm Hg? (Assume there are 1000 grams of water in 1 litre of sea water.)

a) 33.2 mm Hg

b) 32.5 mm Hg

c) 37.0 mm Hg

d) 30.3 mm Hg

e) 32.9 mm Hg

Difficulty: Hard

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

25. Which aqueous solution would be expected to have the highest boiling point?

a) 0.10 M NaCl

b) 0.080 M CaCl₂

c) 0.064 M Fe(NO­₃­)­₃­

d) 0.081 M Fe(NO₃)₂

e) 0.080 M Co(SO₄)

Difficulty: Easy

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

26. In the textbook it was discussed how the melting point is decreased and the boiling point is elevated for a solvent with a solute in it. What happens to the triple point of that solvent? Does the triple point

a) remain at the same pressure and temperature?

b) stay at the same pressure, but warmer temperature?

c) stay at the same pressure, but cooler temperature?

d) occur at a lower pressure and temperature?

e) occur at a higher pressure and temperature?

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

27. Solutions used for intravenous injections must be isotonic, that is, exert an osmotic pressure of 6.9 atm. An isotonic saline solution uses sodium chloride as the solute to achieve isotonic conditions. Use this value for the osmotic pressure to estimate the % NaCl by mass in an isotonic saline solution at 37°C (assume the solution has a density of 1.0 g/mL).

a) 0.40%

b) 0.50%

c) 0.60%

d) 0.80%

e) 0.90%

Difficulty: Easy

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

28. A major component of cell membranes is the phospholipid bilayer. Which of the following statements is(are) FALSE?

1. The bilayer provides a barrier to charged ions

II. Polar molecules such as glucose can pass through the membrane

III. Protein molecules act as gates in the phospholipid bilayer allowing nutrients to enter into the cell

IV. The bilayer consists of two nearly parallel rows with the hydrophobic tails facing out toward the solution and acting as a barrier to water soluble species.

a) all

b) II and I

c) I and III

d) II and IV

e) III and IV

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

29. Which of the following molecules would be suitable surfactants?

1.

2.

3.

4.

a) all

b) 1 and 2

c) 1 and 3

d) 2 and 4

e) 1 and 4

Difficulty: Medium

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

30. Which of the following are true solutions: milk, brass, NaCl in water, sugar in water, ink?

a) milk, NaCl in water, sugar in water

b) milk, brass, NaCl in water, sugar in water

c) NaCl in water, sugar in water, ink

d) brass, NaCl in water, sugar in water

e) NaCl in water, sugar in water

Difficulty: Medium

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

Feedback: a) milk is a colloid suspension; b) as for a); c) ink is a colloid suspension; d)correct answer; e) missing brass, a solid solution

31. Which of the following are colloidal suspensions: fog, milk, sugar in water, salt in water, styrofoam?

a) fog and milk

b) milk, sugar in water, styrofoam

c) fog, sugar in water styrofoam

d) fog, milk, styrofoam

e) fog and styrofoam

Difficulty: Medium

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

Feedback: Colloid suspensions can be liquid, gas, or solid phase.

32. A mixture that does NOT settle out upon standing is

a) solid.

b) a suspension.

c) tyndall solution.

d) a colloid.

e) hydrated.

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

33. Classify the following molecules or fragments as hydrophobic or hydrophilic. A line from an atom indicates where a bond would be formed to another fragment.

1. the -CH₂SO₃^- group
2. CH₃CH₂OH
3. the -CH₂(CH₂)₁₁CH₃ group
4. the -NH₃⁺ group

a) 1; hydrophilic: 2; hydrophilic: 3; hydrophilic: 4; hydrophobic

b) 1; hydrophilic: 2; hydrophobic: 3; hydrophilic: 4; hydrophobic

c) 1; hydrophilic: 2; hydrophilic: 3; hydrophobic: 4; hydrophilic

d) 1; hydrophilic: 2; hydrophobic: 3; hydrophilic: 4; hydrophilic

e) 1; hydrophobic: 2; hydrophilic: 3; hydrophilic: 4; hydrophilic

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

34. Which part of soap is responsible for its ability to mix with oily dirt?

a) the carboxylate end

b) the salt end

c) the hydrophilic end

d) the hydrophobic end

e) the ionized “head”

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

35. Pesticides are non-polar molecules in general. What needs to be done so that farmers are able to spray aqueous solutions containing pesticides?

a) The solutions need to be heated.

b) An emulsifier is added.

c) A miscible agent is added.

d) The solution is shaken frequently.

e) Pesticides will never make a solution with water.

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

ESSAY QUESTIONS

36. A solution is made from dissolving 102 grams of potassium carbonate in 100 grams of water. What is the solvent in this solute in the solution and explain.

Difficulty: Medium

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

37. Determine the mole fraction of a solution made from mixing 39 grams of sugar (MM = 180 g/mol) with 310 grams of water.

Difficulty: Easy

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

38. Industrial grade concentrated HCl is known as muriatic acid and is 31.45% by mass HCl in water. What is the molality of this solution?

Difficulty: Medium

Learning Objective: Work with and interconvert concentration units (mass %, molarity, molality, mole fraction, ppm, and ppb).

Section Reference: 9.1 The Nature of Solutions

39. The molecule drawn below is Vitamin D, Calciferol. Would you predict this molecule to be more soluble in water or body fat and explain why?

Difficulty: Easy

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

40. The molecule drawn below is Vitamin B1, thiamine. Would you predict this molecule to be more soluble in water or body fat and explain why?

Difficulty: Medium

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

41. Pesticides have been found to accumulate and affect the growth of animals higher in food chain. Can you give some rational for this, including discussion of the solubility of pesticides in general?

Difficulty: Medium

Learning Objective: Predict the relative solubilities of a solute in various solvents, and explain in terms of intermolecular forces.

Section Reference: 9.2 Determinants of Solubility

42. When both solid Na metal and solid NaCl are added to water a colourless solution develops. How are these processes different?

Difficulty: Easy

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

44. The problem with hot water heaters in some parts of the country is that a solid forms inside of them, CaCO₃. Predict if the solvation process for CaCO₃ is endothermic or exothermic and if it is more soluble or less soluble at colder temperatures.

Difficulty: Medium

Learning Objective: Calculate and explain solubilities in water.

Section Reference: 9.3 Characteristics of Aqueous Solutions

45. Fahrenheit developed his temperature scale where he set zero degrees as the freezing point for a salt-water solution. What is the concentration of this salt solution in molality (assume NaCl in water)? (T_f = 1.86 ˚C/m)

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

46. Automobile coolant is about 50% by mass ethylene glycol in water. The line structure of ethylene glycol is shown below:

What is the normal boiling point of this solution if K_b for water = 0.512 ˚Cm^-1?

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

47. If you have ever made homemade ice cream you would know that you need to add salt to the ice surrounding the container that you make the ice cream in. By adding the salt to the ice it lowers the temperature of the ice. Explain what is happening to the salt when added to the ice and what you can say about the heat of solvation for sodium chloride.

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

48. When 0.64 g of adrenaline is dissolved in 36.0 g benzene (Kf = 5.12 °C), the freezing point is lowered by 0.50°C. Determine the molecular mass of adrenaline.

Difficulty: Easy

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

49. A 7.85 g sample of a compound with an empirical formula C₁H₁ is dissolved in 172 g of benzene. The freezing point of the solution is 1.50°C below that of pure benzene. Assuming that the compound does not dissociate, what is the molar mass and molecular formula of this compound? The freezing point depression constant for benzene is K_f = 5.12 °C/m.

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

50. To what minimum temperature would a radiator be protected if equal volumes of ethylene glycol (permanent antifreeze) (density 1.11 g/mL) and water were mixed? Assume that ethylene glycol does not dissociate and has a formula, C₂H₆O₂. (K_f = 1.85 ˚Cm^-1).

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

51. What is the freezing point of a solution made from mixing 39 grams of sugar (MM = 180 g/mol) with 310 grams of water? (K_f = 1.85 ˚Cm^-1)?

Difficulty: Easy

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

52. Lysozyme is an enzyme found in tears whose function is to break down bacterial cell walls thus killing the bacteria and protecting the eye from infection. A solution made which contains 0.100 g of lysozyme in 150 g of water ( = 1.00 g/mL) at 25°C has an osmotic pressure of 0.012 bar. What is the molar mass of this enzyme?

Difficulty: Medium

Learning Objective: Understand the reasons for and calculate the magnitudes of colligative properties.

Section Reference: 9.4 Colligative Properties

53. Draw a molecular picture of a surfactant on a waxed surface, like soapy water on a freshly waxed car.

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

54. Ben Franklin determined Avogadro’s number within a factor of 5. He was able to do this by dropping 1 teaspoon of oil on a still pond and determined the area covered by the oil at about ¾ of an acre. You can simulate this by adding 1 drop of soap on the top of a greasy pan in the kitchen and watch the grease move to the sides. Sketch the interaction of the soap with the layer of water and sketch how the soap “dissolves” grease in water.

Difficulty: Easy

Learning Objective: Understand some aspects of colloidal suspensions and surfactant solutions.

Section Reference: 9.5 Between Solutions and Mixtures

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