1 Chapter 13 Properties of Solutions (Brown and LeMay Chapter 13 and Tro Chapter 12) Thirsty Seawater Drinking seawater can cause you to __________________________ Seawater is a homogeneous mixture of ______________ with water. Seawater contains high concentrations of salts o higher than the salt content of your ______________ As seawater passes through your body, it pulls water out of your cells; due mainly to nature’s tendency toward spontaneous mixing This reduces your cells’ water level and usually results in diarrhea as this extra liquid flows out with the seawater Pause the video notes here and open your text book to page 555. Examine Figure 13.24: Osmosis through red blood cell wall. Draw these two pictures here and describe what you see: High solute concentration Low solute concentration Seawater The cell wall acts as a barrier to solute moving so the only way for the seawater and the cell solution to have uniform mixing is for water to flow out of the cells of your intestine and into your digestive tract Solutions Homogeneous mixtures o composition _____________ from one sample to another o appears to be _________________, though really contains multiple materials Most homogeneous materials we encounter are actually __________________ o e.g., __________________ Nature has a tendency toward _________________________ o generally, uniform mixing is more _____________________favorable Solutions When table salt is mixed with water, it seems to disappear, or become a liquid – the mixture is ______________________. o the salt is still there, as you can tell from the taste, or simply boiling away the water Homogeneous mixtures are called __________________ The component of the solution that changes state is called the ______________ The component that keeps its state is called the ____________________ o if both components start in the same state, the major component is the solvent
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Chapter 13 Properties of Solutions (Brown and LeMay Chapter 13 and Tro Chapter 12)
Thirsty Seawater
Drinking seawater can cause you to __________________________
Seawater is a homogeneous mixture of ______________ with water.
Seawater contains high concentrations of salts
o higher than the salt content of your ______________
As seawater passes through your body, it pulls water out of your cells; due mainly to nature’s
tendency toward spontaneous mixing
This reduces your cells’ water level and usually results in diarrhea as this extra liquid flows out
with the seawater
Pause the video notes here and open your text book to page 555. Examine Figure 13.24:
Osmosis through red blood cell wall. Draw these two pictures here and describe what you see:
High solute concentration Low solute concentration
Seawater
The cell wall acts as a barrier to solute moving so the only way for the seawater and the cell solution to
have uniform mixing is for water to flow out of the cells of your intestine and into your digestive tract
Solutions
Homogeneous mixtures
o composition _____________ from one sample to another
o appears to be _________________, though really contains multiple materials
Most homogeneous materials we encounter are actually __________________
o e.g., __________________
Nature has a tendency toward _________________________
o generally, uniform mixing is more _____________________favorable
Solutions
When table salt is mixed with water, it seems to disappear, or become a liquid – the mixture is
______________________.
o the salt is still there, as you can tell from the taste, or simply boiling away the water
Homogeneous mixtures are called __________________
The component of the solution that changes state is called the ______________
The component that keeps its state is called the ____________________
o if both components start in the same state, the major component is the solvent
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Examples of Solutions (provide examples in the far right column)
State of Solute State of Solvent Example
Gas Gas
Gas Liquid
Gas Solid
Liquid Gas
Liquid Liquid
Liquid Solid
Solid Gas
Solid Liquid
Solids Solids
Common Types of Solution
Solutions that contain Hg and some other metal are called amalgams
Solutions that contain metal solutes and a metal solvent are called alloys
Brass
What are the two metals that compose brass?
Solubility
When one substance (solute) dissolves in another (solvent) it is said to be _________________
o salt is soluble in water
o bromine is soluble in methylene chloride
When one substance does not dissolve in another it is said to be ______________
o oil is insoluble in water
The solubility of one substance in another depends on two factors – nature’s tendency toward
mixing, and the types of __________________________________
Spontaneous Mixing
o What does the saying likes dissolved likes mean?
Mixing and the Solution Process: Entropy
o Most processes occur because the end result has _______________________________.
o But formation of a solution does not necessarily __________ the potential energy of the system
o When two ideal gases are put into the same container, they spontaneously mix
o even though the difference in _____________ ______________ is negligible
o The gases mix because the energy of the system is lowered through the release of __________
3
Mixing and the Solution Process: Entropy
o _____________________ is the measure of energy dispersal throughout the system
o Energy has a ________________ drive to spread out over as large a volume as it is allowed
o By each gas expanding to fill the container, it spreads its energy out and _____________ its
entropy
Intermolecular Forces and the Solution Process
o Energy changes in the formation of most solutions also involve
_________________________________________ between the particles
o For the solvent and solute to mix you must overcome
1. all of the ____________________ attractive forces
2. some of the _________________ attractive forces
o both processes are _______________________.
o At least some of the energy to do this comes from making new _____________________
attractions which is _____________________,
Intermolecular Attractions
These forces may contribute to or oppose the formation of a solution: Draw in the examples provided
from the slide:
Dispersion Dipole-Dipole Hydrogen Bond Ion-Dipole
Solution Interactions
Draw the interactions being presented on the slide:
o Relative Interactions and Solution Formation
Fill in the following table
Solute-to-Solvent >
Solute-to-Solvent =
Solute-to-Solvent <
4
o When the solute-to-solvent attractions are ____________ than the sum of the solute-to-solute
and solvent-to-solvent attractions, the solution will only form if the energy difference is small
enough to be overcome by the increase in _____________ from mixing.
Solubility
o There is usually a limit to the solubility of one substance in another
o gases are _____________ soluble in each other
o two liquids that are mutually soluble are said to be ________________
alcohol and water are _________________
oil and water are _________________
o The maximum amount of solute that can be dissolved in a given amount of solvent is called the
__________________________
o The solubility of one substance in another varies with _______________ and _______________
Will It Dissolve?
Chemist’s Rule of Thumb – _______________________________
o A chemical will dissolve in a solvent if it has a _______________ structure to the solvent
o when the solvent and solute structures are similar, the solvent molecules will attract the
solute particles at least as well as the solute particles are attracted to each other
o Polar molecules and ionic compounds will be more soluble in ______________ solvents
o Nonpolar molecules will be more soluble in _________________solvents
Classifying Solvents
Fill in the following table:
Solvent Class Structural Feature
Water
Methyl alcohol
Ethyl alcohol
Acetone
Toluene
Hexane
Diethyl ether
Carbon tetrachloride
Example 12.1a: Predict whether the following vitamin is soluble in fat or water
Draw the structure of Vitamin C
Water is a __________________ solvent. Fat is mostly made of ___________________ molecules.
Is vitamin C water soluble or fat soluble? Explain.
5
Example 12.1b: Predict whether the following vitamin is soluble in fat or water
Draw the structure of Vitamin K
Water is a __________________ solvent. Fat is mostly made of ___________________ molecules.
Is vitamin K water soluble or fat soluble? Explain.
Practice – Decide if the following are more soluble in hexane, C6H14, or water
Naphthalene: Draw the structure here
Is this polar or nonpolar?
Is this molecule soluble in hexane or in water? Explain.
Formaldehyde: Draw the structure here
Is this molecule soluble in hexane or in water? Explain.
Stearic acid: Draw the structure here
Is this molecule soluble in hexane or in water? Explain
Practice – Explain the solubility trends seen in the table below
Explain the trend presented: How does the length of the hydrocarbon chain affect the solubility in polar
solvents such as water, or nonpolar solvent such as hexane?
6
Practice – Explain the solubility trends seen in the table below
o These alcohols all have a ______________ ________ part and a nonpolar _________ part.
o As we go down the table the _________________ part gets larger, but the amount of
___________ stays the same.
o We therefore expect that the solubility in _____________ should decrease and the solubility in
______________ should increase, and it does.
Solution Equilibrium
o The dissolution of a solute in a solvent is an ______________ process
o Initially, when there is no dissolved solute, the only process possible is _______________
o Shortly after some solute is dissolved, solute particles can start to recombine to reform solute
molecules – but the rate of dissolution _______ rate of _____________ and the solute
continues to dissolve
o Eventually, the rate of dissolution ______the rate of deposition – the solution is saturated with
solute and no more solute will dissolve
Solution Equilibrium
(this slide doesn’t show while I am talking about it… sorry)
Solubility Limit
o A solution that has the solute and solvent in dynamic equilibrium is said to be _____________
o if you add more solute it will not dissolve
o the saturation concentration depends on the __________________
and _____________ of gases
o A solution that has less solute than saturation is said to be ________________
o more solute will dissolve at this temperature
o A solution that has more solute than saturation is said to be _____________________
How Can You Make a Solvent Hold More Solute Than It Is Able To?
o Solutions can be made saturated at non-room conditions – then allowed to come to room
conditions slowly
o For some solutes, instead of coming out of solution when the conditions change, they get stuck
in-between the solvent molecules and the solution becomes _____________________
o Supersaturated solutions are _____________ and lose all the solute above saturation when
disturbed
o e.g. shaking a carbonated beverage
Adding a Crystal of NaC2H3O2 to a Supersaturated Solution
Make a comment on what a seed crystal will do to a supersaturated solution:
7
Temperature Dependence of Solubility of Solids in Water
o Solubility is generally given in __________of solute that will dissolve in __________ of water
o For __________ solids, the solubility of the solid increases as the temperature increases
o when Hsolution is endothermic
o Solubility curves can be used to predict whether a solution with a particular amount of solute
dissolved in water is saturated (on the line), unsaturated (below the line), or supersaturated
(above the line)
Solubility Curves
(we practiced reading these curves in our Intermolecular Attractions Chapter earlier)
Purification by Recrystallization
o One of the common operations performed by a chemist is ______________ ____________
from a solid compound
o One method of purification involves _____________ a solid in a hot solvent until the solution is
saturated
o As the solution slowly cools, the solid crystallizes out, leaving impurities behind
Recrystallization of KNO3
o KNO3 can be purified by dissolving a little less then 106 g in 100 g of water at 60 ºC then allowing
it to cool slowly
o When it cools to 0 ºC only 13.9 g will remain in solution, the rest will precipitate out
Practice – Decide if each of the following solutions is saturated, unsaturated, or supersaturated
o 50 grams of KNO3 in 100 g of water at 34 Celsius: __________________
o 50 grams of KNO3 in 100 g of water at 50 Celsius: __________________
o 50 grams of KNO3 in 50 g of water at 50 Celsius: __________________
o 100 grams of NH4Cl in s00 g of water at 70 Celsius: __________________
o 100 grams of KNO3 in 150 g of water at 34 Celsius: __________________
Temperature Dependence of Solubility of Gases in Water
o Gases generally have __________ solubility in water than ionic or polar covalent solids because
most are _______________ molecules
o gases with __________ solubility usually are actually ____________ with water
o For __________ gases, the solubility of the gas decreases as the temperature increases
o the Hsolution is ________________ because you do not need to overcome solute–solute
attractions
Temperature Dependence of Gas Solubility in Water (g/100 g H2O)
Sketch the curve of the solubility vs. temperature for carbon dioxide and acetylene on an x-y axis
8
Pressure Dependence of Solubility of Gases in Water
o The _______________________ of a gas in contact with a liquid, the more soluble the gas is in
the liquid
Henry’s Law
o The solubility of a gas (Sgas) is directly proportional to its partial pressure, (Pgas)
o Sgas = kHPgas
kH is called the _____________________
Record Henry’s Law Constants for the following gases at 25 Celsius:
Oxygen _______________
Nitrogen _____________
Carbon dioxide ______________
Ammonia ________________
helium _________________
Relationship between Partial Pressure and Solubility of a Gas
Graph the Solubility of Gases in water at various pressures for Oxygen and Carbon dioxide on an x-y axis
(Video 2)
Example 12.2: What pressure of CO2 is required to keep the [CO2] = 0.12 M in soda at 25 °C?
Solve and show all work here:
Practice – How many grams of NH3 will dissolve in 0.10 L of solution when its partial pressure is 7.6 torr?
(kH = 58 M/atm)
Solve and show all work here: (This will be covered in two slides)
9
Concentrations (Slide 60)
o Solutions have _________________ composition
o To describe a solution, you need to describe the components ___________ their relative
amounts
o The terms ________ and ____________ can be used as qualitative descriptions of the amount
of solute in solution
o _________________ = amount of solute in a given amount of solution
o occasionally amount of solvent
Solution Concentration Molarity
o Moles of solute per 1 liter of solution
o Used because it describes how many molecules of solute in each liter of solution
o If a sugar solution concentration is 2.0 M, 1 liter of solution contains 2.0 moles of sugar, 2 liters
= 4.0 moles sugar, 0.5 liters = 1.0 mole sugar
Molarity and Dissociation
o The molarity of the ionic compound allows you to determine the molarity of the dissolved ions
o CaCl2(aq) = _________________________
o A 1.0 M CaCl2(aq) solution contains 1.0 moles of CaCl2 in each liter of solution
1 L = __________________________
Solution Concentration Molality, m
Moles of ___________________________
o defined in terms of amount of solvent, not solution
like the others
o Does not vary with _____________________________
because based on _____________________, not volumes
Practice – Calculate the molarity of a solution made by dissolving 34.0 g of NH3 in 2.00 x 103 mL of
solution
(MMNH3 = 17.04 g/mol)
Example 12.4b: What is the molality of a solution prepared by mixing 17.2 g of C2H6O2 with 0.500 kg of
H2O to make 515 mL of solution?
10
Practice – Calculate the molality of a solution made by dissolving 34.0 g of NH3 in 2.00 x 103 mL of water
(MMNH3 = 17.04 g/mol, dH2O = 1.00 g/mL)
Practice – Calculate the molality of 16.2 M H2SO4(aq)
(MMH2SO4 = 98.08 g/mol, dsol’n = 1.80 g/mL)
Colligative Properties
o ____________________ are properties whose value depends only on the number of solute
particles, and not on what they are
o value of the property depends on the ___________________ of the solution
o The difference in the value of the property between the solution and the pure substance is
generally related to the different _______________ and solute particles occupying solvent
molecules positions
Vapor Pressure of Solutions
o The vapor pressure of a solvent above a solution is ___________________ than the vapor
pressure of the pure solvent.
Freezing Salt Water
o Pure water freezes at 0 ºC. At this temperature, ice and liquid water are in ________________.
o Adding salt ________________. The salt particles dissolve in the water, but do not attach easily
to the solid ice.
o When an aqueous solution containing a dissolved solid solute freezes slowly, the ice that forms
does not normally contain much of the solute.
o To return the system to equilibrium, the temperature must be lowered sufficiently to make the
water molecules ______________ enough so that more can attach themselves to the ice.
11
Freezing Point Depression
o The freezing point of a solution is ___________ than the freezing point of the pure solvent
o therefore the melting point of the solid solution is lower
o The difference between the freezing point of the solution and freezing point of the pure
solvent is directly proportional to the molal concentration of solute particles
o The proportionality constant is called the Freezing Point Depression Constant, Kf
the value of Kf depends on the solvent
the units of Kf are °C/m
Kf
Freezing Point Depression and Boiling Point Elevation Constants
Solvent Normal freezing point
Kf (oC/molal) Normal boiling point
Kb (oC/molal)
Benzene
Carbon tetrachloride
Chloroform
Ethanol
Diethyl ether
Water
Example 12.8: What is the freezing point of a 1.7 m aqueous ethylene glycol solution, C2H6O2?
Practice – Calculate the molar mass of a compound if a solution of 12.0 g dissolved in 80.0 g of water
freezes at −1.94 °C
(Kf water = 1.86 °C/m)
12
Boiling Point Elevation
The boiling point of a solution is _____________ than the boiling point of the pure solvent
o for a nonvolatile solute
The difference between the boiling point of the solution and boiling point of the pure solvent is
directly proportional to the molal concentration of solute particles
o The proportionality constant is called the Boiling Point Elevation Constant, Kb
o the value of Kb depends on the solvent
o the units of Kb are °C/m
Example 12.9: How many grams of ethylene glycol, C2H6O2, must be added to 1.0 kg H2O to give a
solution that boils at 105 °C?
Practice – Calculate the boiling point of a solution made by dissolving 1.00 g of glycerin, C3H8O3, in 54.0 g
of water
van’t Hoff Factors
o Ionic compounds produce multiple solute particles for each formula unit
o The theoretical van’t Hoff factor, i, is the ratio of moles of solute particles to moles of formula
units dissolved
o The measured van’t Hoff factors are generally less than the theoretical due to ion pairing in
solution
Example 12.11: What is the freezing point of a if 0.050 m CaCl2(aq)?
13
Example 12.12: A solution contains 0.102 mol Ca(NO3)2 and 0.927 mol H2O. Calculate the boiling point
of this solution:
Practice – Calculate the theoretical boiling point of a solution made by dissolving 10.0 g of NaCl (MM
58.44) in 54.0 g of water
Practice – Calculate the theoretical boiling point of a solution made by dissolving 20.0 g of ammonium
sulfate in 75.0 g of H2O
Osmosis
o ______________ is the flow of solvent from a solution of low concentration into a solution of
high concentration
o The solutions may be separated by a semi-permeable membrane
o A ______________ membrane allows solvent to flow through it, but not solute
Osmotic Pressure
o The amount of pressure needed to keep osmotic flow from taking place is called the
___________________
o The osmotic pressure, _______, is directly proportional to the ___________ of the solute
particles
o R = 0.08206 (atm∙L)/(mol∙K)
o ____________________
Example 12.10: What is the molar mass of a protein if 5.87 mg per 10 mL gives an osmotic pressure of
2.45 torr at 25 °C?
Practice – Lysozyme is an enzyme used to cleave cell walls. A solution made by dissolving 0.0750 g of
lysozyme in 100.0 mL results in an osmotic pressure of 1.32 x 10−3 atm at 25 °C. Calculate the molar
mass of lysozyme.
14
Chapter 13: Colligative Properties Assignment Sheet
Criteria for Credit:
1. Write out the complete question
2. Show the complete solution, showing all work including units
3. Repeat
Lesson # Assigned Problems Due Date
Lesson 1: The Solution Process
13.13, 13.14
Lesson 2: Saturated Solutions, Factors Affecting Solubility
13.20, 13.22, 13.24, 13.26, 13.28, 13.30
Lesson 3: Concentrations of Solutions
13.36c, 13.38, 13.39, 13.40, 13.42 c and d,
Lesson 4: Colligative Properties
13.63 a and b, 13.66, 13.68, 13.70, 13.72, 13.73
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