Transcript Chemistry: Matter and Change

CHEMISTRY
Matter and Change
Chapter 14: Mixtures and Solutions
CHAPTER
14
Table Of Contents
Section 14.2
Solution Concentration
Section 14.3
Factors Affecting Solvation
Section 14.4
Colligative Properties of
Solutions
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SECTION
14.1
Types of Mixtures
• Compare the properties
of suspensions, colloids,
and solutions.
solute: a substance
dissolved in a solution
• Identify types of colloids
and types of solutions.
soluble
miscible
insoluble
immiscible
• Describe the electrostatic
forces in colloids.
Mixtures can be either
heterogeneous or
homogeneous.
SECTION
14.2
Solution Concentration
• Describe concentration
using different units.
• Determine the
concentrations of
solutions.
• Calculate the molarity of
a solution.
solvent: the substance
that dissolves a solute to
form a solution
concentration
molarity
molality
mole fraction
Concentration can be expressed in terms
of percent or in terms of moles.
SECTION
14.2
Solution Concentration
Expressing Concentration
• The concentration of a solution is a
measure of how much solute is dissolved
in a specific amount of solvent or solution.
• Concentration can be described as
concentrated or dilute.
SECTION
14.2
Solution Concentration
Expressing Concentration (cont.)
SECTION
14.2
Solution Concentration
Expressing Concentration (cont.)
Example 1:
In order to maintain a sodium chloride
concentration similar to ocean water, an
aquarium must contain 3.6g NaCl per
100.0g of water. What is the percent by
mass of NaCl?
Ex. 2) What is the percent by volume of
ethanol in a solution that contains 35 mL of
ethanol dissolved in 155 mL of water?
SECTION
14.2
Solution Concentration
Expressing Concentration (cont.)
• Molarity is the number of moles of solute
dissolved per liter of solution.
• Dilution equation: M1V1 = M2V2
Ex. 3) A 100.5-mL intravenous solution
contains 5.10g of glucose. What is the
molarity of this solution? The molar mass of
C6H12O6 is 180.16 g/mol.
SECTION
14.2
Solution Concentration
Expressing Concentration (cont.)
• Molality is the ratio of moles of solute
dissolved in 1 kg of solvent.
• What volume in milliliters of 2.00M calcium
chloride (CaCl2) stock solution would you
use to make 0.50L of 0.0300M calcium
chloride solution?
SECTION
14.2
Solution Concentration
Expressing Concentration (cont.)
• Mole fraction is the ratio of the number of
moles of solute in solution to the total number
of moles of solute and solvent.
SECTION
Solution Concentration
14.2
Expressing Concentration (cont.)
Percentage
by
moles
SECTION
14.2
Section Check
Which is NOT a quantitative measure
of concentration?
A. molarity
B. molality
C. percent by mass
D. dilute
SECTION
14.2
Section Check
The number of moles of solute divided
by liters of solution is called ____.
A. molarity
B. molality
C. percent by volume
D. percent by mass
SECTION
14.3
Factors Affecting Solvation
• Describe how
intermolecular forces
affect solvation.
• Define solubility.
• Understand what
factors affect solubility.
exothermic: a chemical
reaction in which more
energy is released than
is required to break
bonds in the initial
reactants
SECTION
14.3
Factors Affecting Solvation
solvation
heat of solution
unsaturated solution
saturated solution
supersaturated solution
Henry’s law
Factors such as temperature, pressure, and
polarity affect the formation of solutions.
SECTION
14.3
Factors Affecting Solvation
The Solvation Process
• Solvation is the process of surrounding
solute particles with solvent particles to
form a solution.
• Solvation in water is called hydration.
• The attraction between dipoles of a water
molecule and the ions of a crystal are greater
than the attraction among ions of a crystal.
SECTION
14.3
Factors Affecting Solvation
The Solvation Process (cont.)
SECTION
14.3
Factors Affecting Solvation
The Solvation Process (cont.)
• Sucrose molecules have several O–H bonds,
which become sites for hydrogen bonding with
water molecules.
• Oil does not form a
solution with water
because there is little
attraction between
polar water molecules
and nonpolar oil
molecules.
SECTION
14.3
Factors Affecting Solvation
The Solvation Process (cont.)
• During solvation, the solute must separate
into particles and move apart, which
requires energy.
• The overall energy change that occurs during
solution formation is called the heat of
solution.
SECTION
14.3
Factors Affecting Solvation
Factors That Affect Solvation
• Stirring or shaking moves dissolved particles
away from the contact surfaces more quickly and
allows new collisions to occur thereby increasing
the rate of solvation.
• Breaking the solute into small pieces increases
surface area and allows more collisions to occur
thereby increasing the rate of solvation.
• As temperature increases, rate of solvation
increases.
SECTION
14.3
Factors Affecting Solvation
Solubility
• Solubility depends on the nature of the
solute and solvent.
• Unsaturated solutions are solutions that
contain less dissolved solute for a given
temperature and pressure than a saturated
solution.
SECTION
14.3
Factors Affecting Solvation
Solubility (cont.)
• Saturated solutions contain the maximum
amount of dissolved solute for a given
amount of solute at a specific temperature
and pressure.
• Solubility is affected by increasing the
temperature of the solvent because the
kinetic energy of the particles increases.
SECTION
14.3
Factors Affecting Solvation
Solubility (cont.)
SECTION
14.3
Factors Affecting Solvation
Solubility (cont.)
• A supersaturated solution contains more
dissolved solute than a saturated solution
at the same temperature.
• To form a supersaturated solution, a
saturated solution is formed at high
temperature and then slowly cooled.
• Supersaturated solutions are unstable.
SECTION
14.3
Factors Affecting Solvation
Solubility (cont.)
SECTION
14.3
Factors Affecting Solvation
Solubility (cont.)
• Gases are less soluble in liquid solvents at
high temperatures.
• Solubility of gases increases as its external
pressure is increased.
• Henry’s law states that at a given temperature,
the solubility (S) of a gas in a liquid is directly
proportional to the pressure (P).
SECTION
14.3
Section Check
For a given amount, which type of
solution contains the LEAST amount
of solute?
A. solvated
B. saturated
C. supersaturated
D. unsaturated
SECTION
14.3
Section Check
At a given temperature, the solubility of
a gas is directly proportional to what?
A. volume
B. mass
C. molarity
D. pressure
SECTION
14.4
Colligative Properties of Solutions
• Describe colligative
properties.
• Identify four colligative
properties of solutions.
• Determine the boiling
point elevation and
freezing point depression
of a solution.
ion: an atom that is
electrically charged
SECTION
14.4
Colligative Properties of Solutions
colligative property
vapor pressure lowering
boiling point elevation
freezing point depression
osmosis
osmotic pressure
Colligative properties depend on the
number of solute particles in a solution.
SECTION
14.4
Colligative Properties of Solutions
Electrolytes and Colligative Properties
• Colligative properties are physical
properties of solutions that are affected by
the number of particles but not by the
identity of dissolved solute particles.
–Colligative means depending on the collection
–Colligative properties include: vapor pressure
lowering, boiling point elevation, freezing point
depression and osmotic pressure.
SECTION
14.4
Colligative Properties of Solutions
Electrolytes and Colligative Properties (cont.)
• Ionic compounds are electrolytes because they
dissociate in water to form a solution that
conducts electricity.
–Electrolytes that produce many ions are strong
electrolytes.
–Electrolytes that produce only a few ions are weak
electrolytes.
• Many molecular compounds do not ionize when
dissolved, and do not conduct electricity, these
are called nonelectrolytes.
–There are some exceptions, so those molecular
compounds that do ionize are electrolytes.
SECTION
14.4
Colligative Properties of Solutions
Vapor Pressure Lowering
• Adding a nonvolatile solute (one that has
little tendency to become a gas) to a
solvent lowers the solvent’s vapor
pressure.
• When a solute is present, a mixture of solvent
and solute occupies the surface area, and
fewer particles enter the gaseous state.
• The greater the number of solute particles,
the lower the vapor pressure.
SECTION
14.4
Colligative Properties of Solutions
Vapor Pressure Lowering (cont.)
• Vapor pressure lowering is due to the number
of solute particles in solution and is a colligative
property of solutions.
SECTION
14.4
Colligative Properties of Solutions
Boiling Point Elevation
• When a nonvolatile solute lowers the vapor
pressure of a solvent, the boiling point is
also affected.
• More heat is needed to supply additional
kinetic energy to raise the vapor pressure to
atmospheric pressure.
SECTION
14.4
Colligative Properties of Solutions
Boiling Point Elevation (cont.)
• The temperature difference between a
solution’s boiling point and a pure solvent's
boiling point is called the boiling point
elevation.
SECTION
14.4
Colligative Properties of Solutions
Boiling Point Elevation (cont.)
SECTION
14.4
Colligative Properties of Solutions
Freezing Point Depression
• At a solvent's freezing point temperature,
particles no longer have sufficient kinetic
energy to overcome interparticle attractive
forces.
• The freezing point of a
solution is always
lower than that of the
pure solvent.
SECTION
14.4
Colligative Properties of Solutions
Freezing Point Depression (cont.)
• Solute particles interfere with the attractive
forces among solvent particles.
• A solution's freezing point depression is the
difference in temperature between its freezing
point and the freezing point of the pure solvent.
SECTION
14.4
Colligative Properties of Solutions
Freezing Point Depression (cont.)
Examples:
1.) Calculate the freezing point depression
of a solution of 100.g of ethylene glycol
(C2H6O2) antifreeze in 0.500kg of H2O. Kf
for water is 1.86C/m.
2.) When ethylene glycol (C2H6O2) is added to
1675 g of water, the boiling point of the solution
is 104.6C. How many grams of ethylene glycol
were added? Kb for water is 0.52 C/m.
SECTION
14.4
Colligative Properties of Solutions
Osmotic Pressure
• Osmosis is the diffusion of a solvent through a
semipermeable membrane.
SECTION
14.4
Colligative Properties of Solutions
Osmotic Pressure (cont.)
• Osmotic pressure is the amount of additional
pressure caused by water molecules that moved
into the concentrated solution.
SECTION
14.4
Section Check
Nonvolatile solutes ____ the vapor
pressure of a solution.
A. increase
B. decrease
C. do not change
D. unpredictably change
SECTION
14.4
Section Check
Colligative properties of a solution
depend on:
A. the type of solute
B. the type of solvent
C. the vapor pressure of the solvent
D. the number of particles of solute
CHAPTER
Mixtures and Solutions
14
Resources
Chemistry Online
Study Guide
Chapter Assessment
Standardized Test Practice
SECTION
Types of Mixtures
14.1
Study Guide
Key Concepts
• The individual substances in a heterogeneous mixture
remain distinct.
• Two types of heterogeneous mixtures are suspensions
and colloids.
• Brownian motion is the erratic movement of colloid
particles.
• Colloids exhibit the Tyndall effect.
• A solution can exist as a gas, a liquid, or a solid,
depending on the solvent.
• Solutes in a solution can be gases, liquids, or solids.
SECTION
Solution Concentration
14.2
Study Guide
Key Concepts
• Concentrations can be measured qualitatively and
quantitatively.
• Molarity is the number of moles of solute dissolved per
liter of solution.
• Molality is the ratio of the number of moles of solute
dissolved in 1 kg of solvent.
SECTION
Solution Concentration
14.2
Study Guide
Key Concepts
• The number of moles of solute does not change during a
dilution.
M1V1 = M2V2
SECTION
14.3
Factors Affecting Solvation
Study Guide
Key Concepts
• The process of solvation involves solute particles
surrounded by solvent particles.
• Solutions can be unsaturated, saturated, or
supersaturated.
• Henry’s law states that at a given temperature, the
solubility (S) of a gas in a liquid is directly proportional
to the pressure (P) of the gas above the liquid.
SECTION
14.4
Colligative Properties of Solutions
Study Guide
Key Concepts
• Nonvolatile solutes lower the vapor pressure of a
solution.
• Boiling point elevation is directly related to the solution’s
molality.
∆Tb = Kbm
• A solution’s freezing point is always lower than that of the
pure solvent.
∆Tf = Kfm
• Osmotic pressure depends on the number of solute
particles in a given volume.
CHAPTER
14
Mixtures and Solutions
Chapter Assessment
The scattering of light by dispersed solids
in a colloid is known as ____.
A. Tyndall effect
B. Brownian motion
C. Henry’s law
D. Charles’s law
CHAPTER
14
Mixtures and Solutions
Chapter Assessment
Molality is:
A. the number of moles of solute divided by liters
of solution
B. the volume of solute divided by liters of solution
C. the volume of solute divided by the volume of
solution
D. the number of moles of solute divided by kg of
solvent
CHAPTER
14
Mixtures and Solutions
Chapter Assessment
Which is NOT a type of solution?
A. saturated
B. unsaturated
C. polyunsaturated
D. supersaturated
CHAPTER
14
Mixtures and Solutions
Chapter Assessment
The addition of a nonvolatile solute to a
solution:
A. increases the freezing point of the solution
B. increases the vapor pressure of the solution
C. lowers the boiling point of the solution
D. decreases vapor pressure of the solution
CHAPTER
14
Mixtures and Solutions
Chapter Assessment
Solutes in a solution can be:
A. liquids only
B. liquids and solids only
C. gases and solids only
D. gases, liquids, or solids
CHAPTER
14
Mixtures and Solutions
Standardized Test Practice
Which is NOT an intensive physical
property?
A. volume
B. hardness
C. density
D. boiling point
CHAPTER
14
Mixtures and Solutions
Standardized Test Practice
Cl2(g) + 2NO(g) → 2NOCl is what type of
reaction?
A. dehydration
B. synthesis
C. fusion
D. replacement
CHAPTER
Mixtures and Solutions
14
Standardized Test Practice
If 8 mol of H2 is used, how many moles of
Fe will be produced?
Please note: Assume H2 is the limiting reactant
Fe3O4(s) + 4H2 →3Fe(s) + 4H2O(l)
A. 2
B. 3
C. 4
D. 6
CHAPTER
14
Mixtures and Solutions
Standardized Test Practice
Which is NOT a colligative property?
A. heat of solution
B. boiling point elevation
C. vapor pressure lowering
D. freezing point depression
CHAPTER
14
Mixtures and Solutions
Standardized Test Practice
Nonvolatile solutes _____ the boiling
point of a solution.
A. increase
B. decrease
C. do not change
D. unpredictably change
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