prentice hall ©2004 chapter 11 solutions and their properties chapter 11slide 1
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Prentice Hall ©2004
CHAPTER 11CHAPTER 11
SOLUTIONS AND THEIR PROPERTIES
Chapter 11 Slide 1
Prentice Hall ©2004 Chapter 11 Slide 2
• Saturated: Contains the maximum amount of solute that will dissolve in a given solvent.
• Unsaturated: Contains less solute than a solvent has the capacity to dissolve.
• Supersaturated: Contains more solute than would be present in a saturated solution.
• Crystallization: The process in which dissolved solute comes out of the solution and forms crystals.
Solution Formation01Solution Formation01
• Saturated: Contains the maximum amount of solute that will dissolve in a given solvent.
• Unsaturated: Contains less solute than a solvent has the capacity to dissolve.
• Supersaturated: Contains more solute than would be present in a saturated solution.
• Crystallization: The process in which dissolved solute comes out of the solution and forms crystals.
Prentice Hall ©2004 Chapter 11 Slide 3
Solution Formation02Solution Formation02
Prentice Hall ©2004 Chapter 11 Slide 4
Solution Formation02Solution Formation02
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Solution Formation03Solution Formation03
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Solution Formation04Solution Formation04
• Exothermic ∆Hsoln:
• The solute–solvent
interactions are stronger
than solute–solute or
solvent–solvent.
• Favorable process.
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Solution Formation05Solution Formation05
• Endothermic ∆Hsoln:
• The solute–solvent
interactions are weaker
than solute–solute or
solvent–solvent.
• Unfavorable process.
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Solution Formation06Solution Formation06
• Solubility: A measure of how much solute will
dissolve in a solvent at a specific temperature.
• Miscible: Two (or more) liquids that are completely
soluble in each other in all proportions.
• Solvation: The process in which an ion or a
molecule is surrounded by solvent molecules
arranged in a specific manner.
Prentice Hall ©2004 Chapter 11 Slide 9
Solution Formation07Solution Formation07
1. Predict the relative solubilities in the following cases:
(a) Br2 in benzene (C6H6) and in water,
(b) KCl in carbon tetrachloride and in liquid ammonia,
(c) urea (NH2)2CO in carbon disulfide and in water.
2. Is iodine (I2) more soluble in water or in carbon disulfide (CS2)?
3. Which would have the largest (most negative) hydration energy and which should have the smallest? Al3+, Mg2+, Na+
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Concentration Units 01Concentration Units 01
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• Concentration: The amount of solute present in a given amount of solution.
• Percent by Mass (weight percent): The ratio of the mass of a solute to the mass of a solution, multiplied by 100%. % bymassof solute =
mass of solute
mass of solution 100%
mass of solution =mass of solute +mass of solvent
Concentration Units 01Concentration Units 01
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Concentration Units 02Concentration Units 02
• Parts per Million:
• Parts per million (ppm) =
= % mass x 104
• One ppm gives 1 gram of solute per 1,000,000 g or one mg per kg of solution. For dilute aqueous solutions this is about 1 mg per liter of solution.
610xsolutionofmassTotal
componentofMass
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Concentration Units 03Concentration Units 03
• A sample of 0.892 g of potassium chloride (KCl) is
dissolved in 54.6 g of water. What is the percent by
mass of KCl in this solution?
• An aqueous solution is 5.50% H2SO4. How many
moles of sulfuric acid (MM = 98.08 g/mol) are
dissolved in 250.0 g of the solution?
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Concentration Units 04Concentration Units 04
• Mole Fraction (X):
• Molarity (M):
• Molality (m):
moles of number Total Aof MolesAX
SOLUTION of Literssolute of Moles
Molarity
SOLVENT of Kilogramssolute of Moles
=Molality
Prentice Hall ©2004
Units of Concentration Units of Concentration
Mass Percent (mass %)Mass % = (mass of component/total mass of SOLUTION) x 100%
Parts per million, ppm = (mass of component/total mass of SOLUTION) x 106
Parts per billion, ppb = (mass of component / total mass of SOLUTION) x 109
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Concentration Units 06Concentration Units 06
• Molality from Mass: Calculate the molality of a
sulfuric acid solution containing 24.4 g of sulfuric
acid in 198 g of water. The molar mass of sulfuric
acid is 98.08 g.
• Molality from Molarity: Calculate the molality of a
5.86 M ethanol (C2H5OH) solution whose density is
0.927 g/ml.
Prentice Hall ©2004 Chapter 11 Slide 17
Concentration Units 07Concentration Units 07
• Molality from Mass %: Assuming that seawater is
a 3.50 mass % aqueous solution of NaCl, what is
the molality of seawater?
• Molarity from Molality: The density at 20°C of a
0.258 m solution of glucose in water is 1.0173
g/mL, and the molar mass of glucose is 180.2 g.
What is the molarity of the solution?
Prentice Hall ©2004 Chapter 11 Slide 18
Concentration Units
08
Concentration Units
08
• Mole Fraction from Molality: An aqueous
solution is 0.258 m in glucose (MM = 180.2 g/mol).
What is the mole fraction of the glucose?
• Mass from Molality: What mass (in grams) of a
0.500 m aqueous solution of urea [(NH2)2CO, MM
= 60.1 g/mol] would you use to obtain 0.150 mole
of urea?
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Effect of Temperatureon Solubility 01Effect of Temperatureon Solubility 01
• Solids:
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Effect of Temperature on Solubility 02Effect of Temperature on Solubility 02
• Gases:
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• Henry’s Law: • The solubility of a gas is proportional to the pressure of the gas over the solution.
c P
c = k·P
c kP
The Effect of Pressure on theSolubility of Gases 01The Effect of Pressure on theSolubility of Gases 01
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Flash Animation - Click to ContinueFlash Animation - Click to ContinueFlash Animation - Click to ContinueFlash Animation - Click to Continue
The Effect of Pressure on theSolubility of Gases 02The Effect of Pressure on theSolubility of Gases 02
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The Effect of Pressure on theSolubility of Gases 02The Effect of Pressure on theSolubility of Gases 02
• Calculate the molar concentration of O2 in water at 25°C for a
partial pressure of 0.22 atm. The Henry’s law constant for O2
is 3.5 x 10–4 mol/(L·atm).
• The solubility of CO2 in water is 3.2 x 10–2 M at 25°C and 1
atm pressure. What is the Henry’s law constant for CO2 in
mol/(L·atm)?
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Colligative Propertiesof Nonvolatile Solutes 01Colligative Propertiesof Nonvolatile Solutes 01
• Colligative Properties: Depend only on the number of solute particles in solution. These affect properties of the solvent.
• There are four main colligative properties:1. Vapor pressure lowering
2. Freezing point depression
3. Boiling point elevation
4. Osmotic pressure
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Colligative Propertiesof Nonvolatile Solutes 02Colligative Propertiesof Nonvolatile Solutes 02
• When solute molecules displace solvent molecules at the surface, the vapor pressure drops since fewer gas molecules are needed to equalize the escape rate and capture rates at the liquid surface.
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Colligative Propertiesof Nonvolatile Solutes 03Colligative Propertiesof Nonvolatile Solutes 03
• Raoult’s Law: Psoln = P°solv Xsolv
• For a single solute solution, Xsolv= 1 – Xsolute , • We can obtain an expression for the change in vapor
pressure of the solvent (the vapor pressure lowering).Psoln = P°
solv – Psoln
= P°solv – Xsolv P°
solv
= P°solv – (1 – Xsolute ) P°
solv
∆P = Xsolute P°solv
Where superscript o is for pure substance.
Prentice Hall ©2004
Van’t Hoff FactorVan’t Hoff Factor
• For incompletely dissociating ionic solids
• Van’t Hoff Factor i = moles of particles in solution• moles of solute dissolved
•
Chapter 11 Slide 27
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Colligative Propertiesof Nonvolatile Solutes 05Colligative Propertiesof Nonvolatile Solutes 05
• The vapor pressure of a glucose (C6H12O6) solution
is 17.01 mm Hg at 20°C, while that of pure water is 17.25 mm Hg at the same temperature. Estimate the molality of the solution.
• How many grams of NaBr must be added to 250 g of water to lower the vapor pressure by 1.30 mm Hg at 40°C? The vapor pressure of water at 40°C is 55.3 mm Hg.
Prentice Hall ©2004 Chapter 11 Slide 29
Colligative Properties of a Mixture of Two Volatile Liquids 01Colligative Properties of a Mixture of Two Volatile Liquids 01
• What happens if both components are volatile(have measurable vapor pressures)?
• The vapor pressure has a value intermediate between the vapor pressures of the two liquids.PT = PA + PB
= XAP°A + XBP°
B
= XAP°A + (1 – XA)P°
B
PT = P°B + (P°
A – P°B)XA
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Boiling-Point Elevation and Freezing-Point Depression 01Boiling-Point Elevation and Freezing-Point Depression 01
• Boiling-Point Elevation (∆Tb): The boiling point of the solution (Tb) minus the boiling point of the pure solvent (T°
b):
∆Tb = Tb – T°b
∆Tb is proportional to concentration:
∆Tb = Kb mKb = molal boiling-point elevation constant.
Also for incompletely dissociating ionic solids
∆Tb = Kb m i
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Boiling-Point Elevation and Freezing-Point Depression 02Boiling-Point Elevation and Freezing-Point Depression 02
• Freezing-Point Depression (∆Tf): The freezing point of the pure solvent (T°
f) minus the freezing point of the solution (Tf).
∆Tf = T°f – Tf
∆Tf is proportional to concentration:
∆Tf = Kf m Kf = molal freezing-point depression constant.
∆Tb = Kb m i
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Boiling-Point Elevation and Freezing-Point Depression 04Boiling-Point Elevation and Freezing-Point Depression 04
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Boiling-Point Elevation and Freezing-Point Depression 06Boiling-Point Elevation and Freezing-Point Depression 06
• van’t Hoff Factor, i: This factor equals the number of ions produced from each molecule of a compound upon dissolving.
i = 1 for CH3OH i = 3 for CaCl2
i = 2 for NaCl i = 5 for Ca3(PO4)2
• For compounds that dissociate on dissolving, use:
∆Tb = iKb m ∆Tf = iKf m ∆P = ix2 P°1
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Boiling-Point Elevation and Freezing-Point Depression 07Boiling-Point Elevation and Freezing-Point Depression 07
• How many grams of ethylene glycol antifreeze,
CH2(OH)CH2(OH), must you dissolve in one liter of
water to get a freezing point of –20.0°C. The molar
mass of ethylene glycol is 62.01 g. For water, Kf =
1.86 (°C·kg)/mol. What will be the boiling point?
Prentice Hall ©2004 Chapter 11 Slide 35
Boiling-Point Elevation and Freezing-Point Depression 08Boiling-Point Elevation and Freezing-Point Depression 08
• What is the molality of an aqueous solution of KBr
whose freezing point is –2.95°C? Kf for water is 1.86
(°C·kg)/mol.
• What is the freezing point (in °C) of a solution
prepared by dissolving 7.40 g of K2SO4 in 110 g of
water? The value of Kf for water is 1.86 (°C·kg)/mol.
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Osmosis and Osmotic Pressure 01Osmosis and Osmotic Pressure 01
Prentice Hall ©2004 Chapter 11 Slide 37
• Osmosis: The selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
• Osmotic pressure (π or ∏): The pressure required to stop osmosis.
π = iMRT
R = 0.08206 (Latm)/(molK)
Osmosis and Osmotic Pressure 01Osmosis and Osmotic Pressure 01
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Osmosis and Osmotic Pressure 02Osmosis and Osmotic Pressure 02
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Osmosis and Osmotic Pressure 03Osmosis and Osmotic Pressure 03
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Osmosis and Osmotic Pressure 04Osmosis and Osmotic Pressure 04
• Isotonic: Solutions have equal concentration of
solute, and so equal osmotic pressure.
• Hypertonic: Solution with higher concentration of
solute.
• Hypotonic: Solution with lower concentration of
solute.
Prentice Hall ©2004 Chapter 11 Slide 41
Osmosis and Osmotic Pressure 05Osmosis and Osmotic Pressure 05
• The average osmotic pressure of seawater is about
30.0 atm at 25°C. Calculate the molar
concentration of an aqueous solution of urea
[(NH2)2CO] that is isotonic with seawater.
• What is the osmotic pressure (in atm) of a 0.884 M
sucrose solution at 16°C?
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Uses of Colligative Properties 01Uses of Colligative Properties 01
• Desalination:
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Uses of Colligative Properties 02Uses of Colligative Properties 02
• A 7.85 g sample of a compound with the
empirical formula C5H4 is dissolved in 301 g of
benzene. The freezing point of the solution is
1.05°C below that of pure benzene. What are
the molar mass and molecular formula of this
compound?
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Uses of Colligative Properties 03Uses of Colligative Properties 03
• A 202 ml benzene solution containing 2.47 g of an
organic polymer has an osmotic pressure of 8.63
mm Hg at 21°C. Calculate the molar mass of the
polymer.
• What is the molar mass of sucrose if a solution of
0.822 g of sucrose in 300.0 mL of water has an
osmotic pressure of 149 mm Hg at 298 K?
Prentice Hall ©2004 Chapter 11 Slide 45
Uses of Colligative Properties 06Uses of Colligative Properties 06
• Two miscible liquids, A and B, have vapor
pressures of 250 mm Hg and 450 mm Hg,
respectively. They were mixed in equal molar
amounts. What is the total vapor pressure of the
mixture and what are their mole fractions in the
vapor phase?