Solutions - gakall.com · Characteristics of Solutions Return to TOC Section 8.1 In a homogenous...

Chapter 8

Solutions

Chapter 8

Chapter Outline

Copyright ©2016 Cengage Learning. All Rights Reserved. 2

8.1 Characteristics of solutions 8.2 Solubility 8.3 Solution formation 8.4 Solubility rules 8.5 Percent concentration units 8.6 Molarity concentration unit 8.7 Dilution 8.8 Colloidal dispersions and suspensions 8.9 Colligative properties of solutions 8.10 Osmosis and osmotic pressure

Characteristics of Solutions

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Section 8.1

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•  A homogeneous mixture of two or more substances with each substance retaining its own chemical identity

•  Components of a solution: –  Solvent: Component of a solution that is present in

the greatest amount –  Solute: Component of a solution that is present in a

lesser amount relative to that of the solvent •  Substance being dissolved

Solution

Copyright ©2016 Cengage Learning. All Rights Reserved.


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Section 8.1

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Figure 8.1 - Colored Crystals (Solute) Mixed with Water (Solvent)



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Section 8.1

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•  Contains 2 or more components •  Has variable composition •  Properties change as the ratio of solute to

solvent is changed •  Dissolved solutes are present as individual

particles (molecules, atoms, or ions) •  Solutes remain uniformly distributed and will not

settle out with time •  Solute(s) can be separated from the solvent by

physical means such as evaporation

General Properties of a Solution



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Section 8.1

In a homogenous mixture containing 80 mL of water and 20 mL of alcohol, identify the solvent and the solute. a. Water is the solute, and alcohol is the solvent. b. Water is the solvent, and alcohol is the solute. c. Neither, since it is a homogenous mixture. d. Both, since one is dissolving the other.

6 Copyright ©2016 Cengage Learning. All Rights Reserved.


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Section 8.1

In a homogenous mixture containing 80 mL of water and 20 mL of alcohol, identify the solvent and the solute. a. Water is the solute, and alcohol is the solvent. b. Water is the solvent, and alcohol is the solute. c. Neither, since it is a homogenous mixture. d. Both, since one is dissolving the other.


Section 8.2

Solubility

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•  The maximum amount of solute that will dissolve in a given amount of solvent under a given set of conditions


Section 8.2

Solubility

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•  Most solids become more soluble in water with increasing temperature

•  In contrast, gas solubilities in water decrease with increasing temperature

Effect of Temperature on Solubility


Section 8.2

Solubility

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Table 8.1 - Solubilities of Various Compounds in Water at 0°C, 50°C, and 100°C


Section 8.2

Solubility

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•  Pressure has little effect on the solubility of solids and liquids in water

•  Pressure has major effect on the solubility of gases in water

Effect of Pressure on Solubility


Section 8.2

Solubility

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•  The amount of gas that will dissolve in a liquid at a given temperature is directly proportional to the partial pressure of the gas above the liquid –  As the pressure of a gas above the liquid increases,

the solubility of the gas increases

Henry’s Law


Section 8.2

Solubility

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•  A solution that contains the maximum amount of solute that can be dissolved under the conditions at which the solution exists

Saturated Solution


Section 8.2

Solubility

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•  An unstable solution that temporarily contains more dissolved solute than that present in a saturated solution –  Excess solute crystallizes out with time and the

solution reverts to a saturated solution

Supersaturated Solution


Section 8.2

Solubility

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•  A solution that contains less than the maximum amount of solute that can be dissolved under the conditions at which the solution exists –  Most commonly encountered solutions fall into this

category

Unsaturated Solution


Section 8.2

Solubility

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•  Concentrated solution: A solution that contains a large amount of solute relative to the amount that could dissolve

•  Dilute solution: A solution that contains a small amount of solute relative to the amount that could dissolve

Concentrated and Dilute Solutions


Section 8.2

Solubility

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Figure 8.4 - Concentrated and Dilute Solutions


Section 8.2

Solubility

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•  Aqueous solution: A solution in which water is the solvent

•  Nonaqueous solution: A solution in which a substance other than water is the solvent

Aqueous and Nonaqueous Solutions


Section 8.2

Solubility

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How does the temperature and pressure affect the solubility of a gas in water?

a. Increased temperature decreases gas solubility, and increased pressure increases gas solubility. b. Increased temperature increases gas solubility, and increased pressure increases gas solubility. c. Increased temperature decreases gas solubility, and increased pressure decreases gas solubility. d. Decreased temperature decreases gas solubility, and decreased pressure increases gas solubility.


Section 8.2

Solubility

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How does the temperature and pressure affect the solubility of a gas in water?

a. Increased temperature decreases gas solubility, and increased pressure increases gas solubility. b. Increased temperature increases gas solubility, and increased pressure increases gas solubility. c. Increased temperature decreases gas solubility, and increased pressure decreases gas solubility. d. Decreased temperature decreases gas solubility, and decreased pressure increases gas solubility.


Section 8.3

Solution Formation

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•  Two types of interparticle attractions must be overcome: –  Attractions between solute particles (solute–solute

attractions) –  Attractions between solvent particles (solvent–

solvent attractions) •  New type of interaction arises

–  Attraction between solute and solvent particles (solute–solvent attractions)

For a Solute to Dissolve in a Solvent


Section 8.3

Solution Formation

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1.  The state of subdivision of the solute 2.  The degree of agitation during solution

preparation 3.  The temperature of the solution components

Factors Affecting the Rate of Solution Formation


Section 8.3

Solution Formation

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What three factors increase the rate of solution formation? a. State of subdivision of the solute; increase in rate of solute–solvent interaction; decrease in temperature b. State of subdivision of the solute; decrease in rate of solute–solvent interaction; decrease in temperature c. State of subdivision of the solute; decrease in rate of solute–solvent interaction; increase in temperature d. State of subdivision of the solute; increase in rate of solute–solvent interaction; increase in temperature


Section 8.3

Solution Formation

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What three factors increase the rate of solution formation? a. State of subdivision of the solute; increase in rate of solute–solvent interaction; decrease in temperature b. State of subdivision of the solute; decrease in rate of solute–solvent interaction; decrease in temperature c. State of subdivision of the solute; decrease in rate of solute–solvent interaction; increase in temperature d. State of subdivision of the solute; increase in rate of solute–solvent interaction; increase in temperature


Section 8.4

Solubility Rules

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•  In general, it is found that the greater the difference in solute–solvent polarity, the less soluble is the solute

•  Substances of like polarity tend to be more soluble in each other than substances that differ in polarity –  “Like dissolves like” (but not in all cases) –  Use table 8.2 - Solubility guidelines for ionic

compounds in water


Section 8.4

Solubility Rules

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Table 8.2 - Solubility Guidelines for Ionic Compounds in Water


Section 8.4

Solubility Rules

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Greater difference in solute–solvent polarity results in: a. greater solubility of the solute. b. less solubility of the solute. c. no effect on the solubility of the solute. d. an increase in the solvent’s ability to dissolve the solute.


Section 8.4

Solubility Rules

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Greater difference in solute–solvent polarity results in: a. greater solubility of the solute. b. less solubility of the solute. c. no effect on the solubility of the solute. d. an increase in the solvent’s ability to dissolve the solute.


Section 8.4

Solubility Rules

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Concept Check

•  Which of the following ions that are generally soluble in water form compounds with Pb2+?

a)  S2–

b)  Cl–

c)  NO3–

d)  SO42–

e)  Na+


Section 8.4

Solubility Rules

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Concept Check

•  Which of the following ions that are generally soluble in water form compounds with Pb2+?

a)  S2–

b)  Cl–

c)  NO3–

d)  SO42–

e)  Na+


Section 8.5

Percent Concentration Units

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•  The amount of solute present in a specified amount of solution

•  Two methods of expressing concentration: –  Percent concentration –  Molarity concentration

Concentration


Section 8.5


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•  Three different ways of representing percent concentration: –  Percent by mass (mass–mass percent) –  Percent by volume (volume–volume percent) –  Mass–volume percent

Percent Concentration


Section 8.5


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Percent by Mass

mass of solutePercent by mass = × 100mass of solution

Mass of solution = mass of solute + mass of solvent


Section 8.5


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Exercise

•  What is the percent by mass concentration of glucose in a solution made by dissolving 5.5 g of glucose in 78.2 g of water?


Section 8.5


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Exercise

•  What is the percent by mass concentration of glucose in a solution made by dissolving 5.5 g of glucose in 78.2 g of water?

6.6%


Section 8.5


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Percent by Volume

volume of solutePercent by volume = ×100volume of solvent


Section 8.5


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Exercise

•  Calculate the volume percent of solute in 30.0 mL of methyl alcohol in enough water to give 435 mL of solution.


Section 8.5


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Exercise

•  Calculate the volume percent of solute in 30.0 mL of methyl alcohol in enough water to give 435 mL of solution.

6.90%


Section 8.5


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Mass–Volume Percent

( )( )

mass of solute gMass – volume percent = × 100

volume of solution mL


Section 8.5


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Table 8.3 - Conversion Factors Obtained From Percent Concentration Units


Section 8.5


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A solution having a mass percent concentration of 10% contains: a. 10 g of solute and 90 g of solvent. b. 10 g of solvent and 10 g of solute. c. 10 g of solute per 100 g of solvent. d. 10 g of solvent per 100 g of solute.


Section 8.5


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A solution having a mass percent concentration of 10% contains: a. 10 g of solute and 90 g of solvent. b. 10 g of solvent and 10 g of solute. c. 10 g of solute per 100 g of solvent. d. 10 g of solvent per 100 g of solute.


Section 8.5


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How many grams of sodium chloride are needed to prepare 150 mL of 0.9% (m/v) sodium chloride? a. 135 g b. 13.5 g c. 1.35 g d. 0.135 g


Section 8.5


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How many grams of sodium chloride are needed to prepare 150 mL of 0.9% (m/v) sodium chloride? a. 135 g b. 13.5 g c. 1.35 g d. 0.135 g


Section 8.6

Molarity Concentration Unit

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Molarity

•  Moles of solute in a solution divided by the liters of solution

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( ) moles of soluteMolarity M =liters of solution


Section 8.6


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What is the definition of molarity? a. Moles of solute per mole of solution b. Moles of solute per liter of solution c. Liters of solute per mole of solution d. Liters of solute per liter of solution


Section 8.6


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What is the definition of molarity? a. Moles of solute per mole of solution b. Moles of solute per liter of solution c. Liters of solute per mole of solution d. Liters of solute per liter of solution


Section 8.6


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Exercise

•  You have 1.00 mol of sugar in 125.0 mL of solution. Calculate the concentration in units of molarity.


Section 8.6


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Exercise

•  You have 1.00 mol of sugar in 125.0 mL of solution. Calculate the concentration in units of molarity.

8.00 M


Section 8.6


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Exercise

•  You have a 10.0 M sugar solution. What volume of this solution do you need to have 2.00 mol of sugar?


Section 8.6


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Exercise

•  You have a 10.0 M sugar solution. What volume of this solution do you need to have 2.00 mol of sugar?

0.200 L


Section 8.6


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Exercise

•  Consider separate solutions of NaOH and KCl made by dissolving 100.0 g of each solute in 250.0 mL of solution. Calculate the concentration of each solution.


Section 8.6


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Exercise

•  Consider separate solutions of NaOH and KCl made by dissolving 100.0 g of each solute in 250.0 mL of solution. Calculate the concentration of each solution.

10.0 M NaOH

5.37 M KCl


Section 8.7

Dilution

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•  The process in which more solvent is added to a solution in order to lower its concentration

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Concentration of volume of concentration of volume of × = ×

stock solution stock solution diluted solution diluted solution

s C × V

⎛ ⎞ ⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠

s d d= C × V


Section 8.7

Dilution

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How would you prepare 100 mL of 0.9% saline solution in water from a 10% saline solution?

a. 90 mL of 10% saline solution + 100 mL of water b. 90 mL of 10% saline solution + 10 mL of water c. 9 mL of 10% saline solution + 100 mL of water d. 9 mL of 10% saline solution + 91 mL of water


Section 8.7

Dilution

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How would you prepare 100 mL of 0.9% saline solution in water from a 10% saline solution?

a. 90 mL of 10% saline solution + 100 mL of water b. 90 mL of 10% saline solution + 10 mL of water c. 9 mL of 10% saline solution + 100 mL of water d. 9 mL of 10% saline solution + 91 mL of water


Section 8.7

Dilution

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Concept Check

•  A 0.50 M solution of sodium chloride sits on a lab bench. Which of the following would decrease the concentration of the salt solution?

a)  Add water to the solution. b)  Pour some of the solution down the sink drain. c)  Add more sodium chloride to the solution. d)  Let the solution sit out in the open air for a couple of days. e)  At least two of the above would decrease the concentration

of the salt solution.


Section 8.7

Dilution

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Concept Check

•  A 0.50 M solution of sodium chloride sits on a lab bench. Which of the following would decrease the concentration of the salt solution?

a)  Add water to the solution. b)  Pour some of the solution down the sink drain. c)  Add more sodium chloride to the solution. d)  Let the solution sit out in the open air for a couple of days. e)  At least two of the above would decrease the concentration

of the salt solution.


Section 8.7

Dilution

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Exercise

•  What is the minimum volume of a 2.00 M NaOH solution needed to make 150.0 mL of a 0.800 M NaOH solution?


Section 8.7

Dilution

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Exercise

•  What is the minimum volume of a 2.00 M NaOH solution needed to make 150.0 mL of a 0.800 M NaOH solution?

60.0 mL


Section 8.8

Colloidal Dispersions and Suspensions

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Colloidal Dispersion

•  A homogeneous mixture that contains dispersed particles that are intermediate in size between those of a true solution and those of an ordinary heterogeneous mixture –  Dispersed phase (similar to the solute) –  Dispersing medium (similar to the solvent)


Section 8.8


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Tyndall Effect

•  The light-scattering phenomenon that causes the path of a beam of visible light through a colloidal dispersion to be observable –  When we shine a beam of light through a true

solution, we cannot see the track of the light –  A beam of light passing through a colloidal dispersion

can be observed because the light is scattered by the dispersed phase


Section 8.8


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Figure 8.10 - Scattering of Light in a Colloidal Dispersion vs. a True Solution


Section 8.8


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Suspension

•  A heterogeneous mixture that contains dispersed particles that are heavy enough that they settle out under the influence of gravity


Section 8.8


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Table 8.4 - Property Comparison for Solutions, Colloidal Dispersions, and Suspensions


Section 8.8


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What is a colloidal dispersion?

a. It is a mixture that contains small particles not visible to the naked eye. b. It is a mixture that contains particles that do not settle out under the influence of gravity. c. It is a mixture that contains particles that cannot be filtered out through large pore filter paper. d. All of these.


Section 8.8


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What is a colloidal dispersion?

a. It is a mixture that contains small particles not visible to the naked eye. b. It is a mixture that contains particles that do not settle out under the influence of gravity. c. It is a mixture that contains particles that cannot be filtered out through large pore filter paper. d. All of these.


Section 8.9

Colligative Properties of Solutions

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Colligative Property

•  A physical property of a solution that depends only on the number of solute particles (molecules or ions) present in a given quantity of solvent and not on their chemical identities –  Lowering of vapor-pressure –  Elevation of boiling-point –  Depression of freezing-point –  Osmotic pressure


Section 8.9


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Vapor-Pressure Lowering

•  Adding a nonvolatile solute to a solvent lowers the vapor pressure of the resulting solution below that of the pure solvent at the same temperature


Section 8.9


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Figure 8.11 - Surface of Liquid Solvent (a) Before and (b) After Addition of Solute


Section 8.9


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Boiling-Point Elevation

•  Adding a nonvolatile solute to a solvent raises the boiling point of the resulting solution above that of the pure solvent


Section 8.9


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Freezing-Point Depression

•  Adding a nonvolatile solute to a solvent lowers the freezing point of the resulting solution below that of the pure solvent


Section 8.9


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How does the addition of a nonvolatile solute to a solvent affect the vapor pressure of the resulting solution? a. Decreases the vapor pressure b. Increases the vapor pressure c. Has no affect on the vapor pressure d. No correct response


Section 8.9


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How does the addition of a nonvolatile solute to a solvent affect the vapor pressure of the resulting solution? a. Decreases the vapor pressure b. Increases the vapor pressure c. Has no affect on the vapor pressure d. No correct response


Section 8.10

Osmosis and Osmotic Pressure

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Osmosis

•  The passage of a solvent through a semipermeable membrane separating a dilute solution (or pure solvent) from a more concentrated solution –  Semi-permeable membrane: A membrane that

allows certain types of molecules to pass through it but prohibits the passage of other types of molecules


Section 8.10


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Figure 8.13 - An Illustration of the Process of Osmosis


Section 8.10


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Figure 8.14 - An Illustration of a Semi-Permeable Membrane


Section 8.10


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Osmotic Pressure

•  The pressure that must be applied to prevent the net flow of solvent through a semipermeable membrane from a solution of lower solute concentration to a solution of higher solute concentration


Section 8.10


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Osmolarity

•  Used to compare the osmotic pressures of solutions

•  i is the number of particles produced from the

dissociation of one formula unit of solute

79

Osmolarity = molarity × i


Section 8.10


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Exercise

•  What is the osmolarity of a 3 M NaCl solution?


Section 8.10


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Exercise

•  What is the osmolarity of a 3 M NaCl solution?

6 osmol


Section 8.10


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Hypotonic Solution

•  A solution with a lower osmotic pressure than that within cells


Section 8.10


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Hypertonic Solution

•  A solution with a higher osmotic pressure than that within cells


Section 8.10


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Isotonic Solution

•  A solution with an osmotic pressure that is equal to that within cells


Section 8.10


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Figure 8.17 - Effects of Bathing Red Blood Cells in Various Types of Solutions


Section 8.10


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Table 8.5 - Characteristics of Hypotonic, Hypertonic, and Isotonic Solutions


Section 8.10


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What is an isotonic solution? a. A solution with a lower osmotic pressure than that within cells b. A solution with a higher osmotic pressure than that within cells c. A solution with an osmotic pressure equal to that within cells d. A solution which results in a flow of water out of cells


Section 8.10


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What is an isotonic solution? a. A solution with a lower osmotic pressure than that within cells b. A solution with a higher osmotic pressure than that within cells c. A solution with an osmotic pressure equal to that within cells d. A solution which results in a flow of water out of cells


Section 8.10


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How is the osmolarity of a solution determined?

a. Calculate the molarity of the solution, since a solution’s osmolarity is equal to its molarity. b. Divide the molarity of the solution by the number of particles produced per formula unit if the solute dissociates. c. Multiply the molarity of the solution by the number of particles produced per formula unit if the solute dissociates. d. Add the number of dissociated solute particles to the molarity of the solution.


Section 8.10


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How is the osmolarity of a solution determined?

a. Calculate the molarity of the solution, since a solution’s osmolarity is equal to its molarity. b. Divide the molarity of the solution by the number of particles produced per formula unit if the solute dissociates. c. Multiply the molarity of the solution by the number of particles produced per formula unit if the solute dissociates. d. Add the number of dissociated solute particles to the molarity of the solution.


Chapter 8

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Concept Question 1

How would you prepare 200 mL of a 0.8 M sodium hydroxide, molar mass = 40 g/mole, solution in water? Identify the solute and solvent. a. Add 64 g of sodium hydroxide to 200 mL of water. The solvent is water, and the solute is sodium hydroxide. b. Add 64 g of sodium hydroxide to 200 mL of water. The solvent is sodium hydroxide, and the solute is water. c. Add 6.4 g of sodium hydroxide to 200 mL of water. The solvent is water, and the solute is sodium hydroxide. d. Add 6.4 g of sodium hydroxide to 200 mL of water. The solvent is sodium hydroxide, and the solute is water.


Chapter 8

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Concept Question 1

How would you prepare 200 mL of a 0.8 M sodium hydroxide, molar mass = 40 g/mole, solution in water? Identify the solute and solvent. a. Add 64 g of sodium hydroxide to 200 mL of water. The solvent is water, and the solute is sodium hydroxide. b. Add 64 g of sodium hydroxide to 200 mL of water. The solvent is sodium hydroxide, and the solute is water. c. Add 6.4 g of sodium hydroxide to 200 mL of water. The solvent is water, and the solute is sodium hydroxide. d. Add 6.4 g of sodium hydroxide to 200 mL of water. The solvent is sodium hydroxide, and the solute is water.


Chapter 8

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Concept Question 2

If you add 2.6 g of sodium chloride, molar mass = 58 g/mole, to 300 mL water, what is the molarity, percent (m/v), and osmolarity of this solution? a. 0.15 M, 0.9%, and 0.30 osmol b. 0.15 M, 8.7%, and 0.30 osmol c. 0.045 M, 0.09%, and 0.09 osmol d. 0.15 M, 0.9%, and 0.075 osmol


Chapter 8

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Concept Question 2

If you add 2.6 g of sodium chloride, molar mass = 58 g/mole, to 300 mL water, what is the molarity, percent (m/v), and osmolarity of this solution? a. 0.15 M, 0.9%, and 0.30 osmol b. 0.15 M, 8.7%, and 0.30 osmol c. 0.045 M, 0.09%, and 0.09 osmol d. 0.15 M, 0.9%, and 0.075 osmol


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