Unit 8- The Kinetic theory and BEHAVIOR OF GASES.ppt

BEHAVIOR OF GASES
BEHAVIOR OF GASES
Unit 8
Unit 8
Chemistry
Chemistry
Langley
Langley
**Corresponds to Chapter 14 in the Prentice Hall Chemistry Book

PROPERTIES OF GASES
PROPERTIES OF GASES
 No definite shape/volume
No definite shape/volume
 Expands to fill its container
Expands to fill its container
 Easily compressed (squeezed into a
Easily compressed (squeezed into a
smaller container)
smaller container)
 Compressibility is a measure of how much
Compressibility is a measure of how much
the volume of matter decreases under
the volume of matter decreases under
pressure
pressure
 Gases are easily compressed because of
Gases are easily compressed because of
the space between the particles in a gas
the space between the particles in a gas

PROPERTIES OF A GAS
PROPERTIES OF A GAS
 Factors Affecting Gas Pressure
Factors Affecting Gas Pressure
 Amount of Gas
Amount of Gas
 Increase amount, increase pressure
Increase amount, increase pressure
 Volume
Volume
 Reduce volume, increase pressure
Reduce volume, increase pressure
 Temperature
Temperature
 Increase temperature, increase pressure
Increase temperature, increase pressure
 Relationship between pressure,
Relationship between pressure,
temperature, and volume is explained
temperature, and volume is explained
through the Gas Laws
through the Gas Laws

GAS LAWS
GAS LAWS
 Boyle’s Law
Boyle’s Law
 Charles’ Law
Charles’ Law
 Gay-Lussac’s Law
Gay-Lussac’s Law
 Combined Gas Law
Combined Gas Law
 Ideal Gas Law
Ideal Gas Law
 Dalton’s Law of Partial Pressure
Dalton’s Law of Partial Pressure
 Graham’s Law
Graham’s Law

BOYLE’S LAW
BOYLE’S LAW
 If the temperature is constant, as the
If the temperature is constant, as the
pressure of a gas increases, the volume
pressure of a gas increases, the volume
decreases
decreases
 For a given mass of gas at constant
For a given mass of gas at constant
temperature, the volume of a gas varies
temperature, the volume of a gas varies
inversely with pressure
inversely with pressure
 As volume goes up, pressure goes down
As volume goes up, pressure goes down
 As volume goes down, pressure goes up
As volume goes down, pressure goes up
 P
P1
1V
V1
1 = P
= P2
2V
V2
2

BOYLE’S LAW
BOYLE’S LAW
 Real Life Example
Real Life Example
 As you push on the end of a syringe, the
As you push on the end of a syringe, the
volume inside the syringe decreases as the
volume inside the syringe decreases as the
pressure on the syringe increases
pressure on the syringe increases
 Mathematical Example 1:
Mathematical Example 1:
 P
P1
1 = 758 torr
= 758 torr V
V1
1 = 5.0L
= 5.0L P
P2
2
= ?
= ? V
V2
2 = 3.5L
= 3.5L

BOYLE’S LAW
BOYLE’S LAW
 Mathematical Example 2
Mathematical Example 2
 If 4.41 dm
If 4.41 dm3
3
of nitrogen gas are collected at a
of nitrogen gas are collected at a
pressure of 94.2 kPa, what will the volume
pressure of 94.2 kPa, what will the volume
be for this gas at standard pressure if the
be for this gas at standard pressure if the
temperature does not change?
temperature does not change?

CHARLES’ LAW
CHARLES’ LAW
 As the temperature of an enclosed gas
As the temperature of an enclosed gas
increases, the volume increases, if the
increases, the volume increases, if the
pressure is constant
pressure is constant
 The volume of a fixed mass of gas is directly
The volume of a fixed mass of gas is directly
proportional to its Kelvin temperature if the
proportional to its Kelvin temperature if the
pressure is kept constant
pressure is kept constant
 As volume goes up/down, temperature goes
As volume goes up/down, temperature goes
up/down
up/down
 V
V1
1 = V
= V2
2
Temperature must be in
Kelvin! T
Kelvin! T1
1 T
T2
2

CHARLES’ LAW
CHARLES’ LAW
Real Life Example
 Balloon Lab-As the temperature of the water
Balloon Lab-As the temperature of the water
is increased, the volume of the balloon is
is increased, the volume of the balloon is
increased.
increased.
 Coke Can-Fill a coke can with a small
Coke Can-Fill a coke can with a small
amount of water, as you heat the water
amount of water, as you heat the water
inside to near boiling, immediately invert the
inside to near boiling, immediately invert the
coke can into ice-cold water so the coke can
coke can into ice-cold water so the coke can
is experiencing a dramatic drop in
is experiencing a dramatic drop in
temperature, volume of can will decrease
temperature, volume of can will decrease
(can will crush in on itself)
(can will crush in on itself)

CHARLES’ LAW
CHARLES’ LAW
 V
V1
1 = 250mL T
= 250mL T1
1 = 300K
= 300K V
V2
2 =
=
321mL T
321mL T2
2 = ?
= ?
 With a constant pressure, the volume of a gas
With a constant pressure, the volume of a gas
is increased from 15.0L to 32.0L. If the new
is increased from 15.0L to 32.0L. If the new
temperature is 20.0°C, what was the original
temperature is 20.0°C, what was the original
temperature?
temperature?

GAY-LUSSAC’S LAW
GAY-LUSSAC’S LAW
 As the temperature of an enclosed gas
As the temperature of an enclosed gas
increases, the pressure increases, if the volume
increases, the pressure increases, if the volume
is constant
is constant
 The pressure of a gas is directly proportional to
The pressure of a gas is directly proportional to
the Kelvin temperature if the volume remains
the Kelvin temperature if the volume remains
constant
constant
 P
P1
1 = P
= P2
2 Temperature must be in Kelvin! T
Temperature must be in Kelvin! T1
1
T
T2
2

GAY-LUSSAC’S LAW
GAY-LUSSAC’S LAW
Real Life Example
 Tires
Tires
 The faster a car goes, the higher the temperature
The faster a car goes, the higher the temperature
of the tire gets and the higher the pressure inside
of the tire gets and the higher the pressure inside
the tires
the tires
 P
P1
1 = ?
= ? T
T1
1 = 456K
= 456K
P
P2
2 = 789mmHg
= 789mmHg T
T2
2 = 326K
= 326K

GAY-LUSSAC’S LAW
GAY-LUSSAC’S LAW
 The pressure in a tire is 1.8 atm at 20°C.
The pressure in a tire is 1.8 atm at 20°C.
After a 200 mile trip, the pressure reading for
After a 200 mile trip, the pressure reading for
the tire is 1.9 atm. What is the temperature
the tire is 1.9 atm. What is the temperature
inside the tire at that new pressure?
inside the tire at that new pressure?

COMBINED GAS LAW
COMBINED GAS LAW
 Combines Boyle’s, Charles’, and Gay-Lussac’s
Combines Boyle’s, Charles’, and Gay-Lussac’s
laws
laws
 Describes the relationship among temperature,
Describes the relationship among temperature,
pressure, and volume of an enclosed gas
pressure, and volume of an enclosed gas
 Allows you to perform calculation for situations
Allows you to perform calculation for situations
IF and ONLY IF the amount of gas is constant
IF and ONLY IF the amount of gas is constant
 P
P1
1V
V1
1 = P
= P2
2V
V2
2
Kelvin!
Kelvin!
T
T1
1 T
T2
2

IDEAL GAS LAW
IDEAL GAS LAW
 When you need to account for the number of
When you need to account for the number of
moles of gas in addition to pressure,
moles of gas in addition to pressure,
temperature, and volume, you will use the Ideal
temperature, and volume, you will use the Ideal
Gas Equation
Gas Equation
 Modified version of the Combined Gas Law
Modified version of the Combined Gas Law
 PV = nRT
PV = nRT
 n = number of moles
n = number of moles
 R = ideal gas constant
R = ideal gas constant
 0.08206 (L-atm/mol-K)
0.08206 (L-atm/mol-K)
 62.4 (L-mmHg/mol-K)
62.4 (L-mmHg/mol-K)
 8.314 (L-kPa/mol-K)
8.314 (L-kPa/mol-K)

IDEAL GAS LAW
IDEAL GAS LAW
 What is the pressure in atm exerted by 0.5
What is the pressure in atm exerted by 0.5
moles of N
moles of N2
2 in a 10L container at 298
in a 10L container at 298
Kelvin?
Kelvin?
 What is the volume in liters of 0.250 moles
What is the volume in liters of 0.250 moles
of O
of O2
2 at 20°C and 0.974 atm?
at 20°C and 0.974 atm?

IDEAL GAS LAW
IDEAL GAS LAW
 What is the temperature of 76 grams of Cl
What is the temperature of 76 grams of Cl2
2 in
in
a 24L container at 890mmHg?
a 24L container at 890mmHg?
 A deep underground cavern contains
A deep underground cavern contains
2.24x10
2.24x106
6
L of CH
L of CH4
4 at a pressure of
at a pressure of
1.50x10
1.50x103
3
kPa and a temperature of 315K.
kPa and a temperature of 315K.
How many kilograms of CH
How many kilograms of CH4
4 does the cavern
does the cavern
contain?
contain?

IDEAL vs. REAL GASES
IDEAL vs. REAL GASES
 Ideal gases follow the gas laws at all
Ideal gases follow the gas laws at all
conditions of pressure and temperature
conditions of pressure and temperature
 Conforms exactly to the all the assumptions
Conforms exactly to the all the assumptions
of the kinetic theory (no volume, no particle
of the kinetic theory (no volume, no particle
attraction)
attraction)
doesn’t exist
doesn’t exist
 Real gases differ mostly from an ideal
Real gases differ mostly from an ideal
gas at low temperature and high
gas at low temperature and high
pressure
pressure
 Under other conditions, behave as an ideal
Under other conditions, behave as an ideal
gas would
gas would

DALTON’S LAW
DALTON’S LAW
 In a mixture of gases, the total pressure is the
In a mixture of gases, the total pressure is the
sum of the partial pressure of the gases
sum of the partial pressure of the gases
 Partial pressure is the contribution each gas in a
Partial pressure is the contribution each gas in a
mixture makes to the total pressure
mixture makes to the total pressure
 At constant volume and temperature, the total
At constant volume and temperature, the total
pressure exerted by a mixture of gases is
pressure exerted by a mixture of gases is
equal to the sum of the partial pressures of the
equal to the sum of the partial pressures of the
component of gases
component of gases
 P
Ptotal
total = P
= P1
1 + P
+ P2
2 + P
+ P3
3 + …
+ …

DALTON’S LAW
DALTON’S LAW
 In a container there are 4 gases with the
In a container there are 4 gases with the
following pressures: Gas 1-2.5 atm, Gas 2-
following pressures: Gas 1-2.5 atm, Gas 2-
1.9 atm, Gas 3-798 mmHg, Gas 4-2.1 atm;
1.9 atm, Gas 3-798 mmHg, Gas 4-2.1 atm;
find the total pressure in the container.
find the total pressure in the container.

DALTON’S LAW
DALTON’S LAW
 In a sample of HCl gas, the pressure of the
In a sample of HCl gas, the pressure of the
gas is found to be 0.87 atm. If hydrogen
gas is found to be 0.87 atm. If hydrogen
makes up 34% of the gas, what is the
makes up 34% of the gas, what is the
pressure of the hydrogen?
pressure of the hydrogen?

GRAHAM’S LAW
GRAHAM’S LAW
 The ratio of the speeds of two gases at the
The ratio of the speeds of two gases at the
same temperature is equal to the square root
same temperature is equal to the square root
of the inverted molar masses
of the inverted molar masses
 The relative rate of diffusion
The relative rate of diffusion
 Diffusion is the tendency of molecules to move
Diffusion is the tendency of molecules to move
toward areas of lower concentration to areas of
toward areas of lower concentration to areas of
higher concentration until the concentration is
higher concentration until the concentration is
uniform throughout
uniform throughout
 Gases of lower molar mass diffuse and effuse faster
Gases of lower molar mass diffuse and effuse faster
than gases of higher molar mass
than gases of higher molar mass
 Effusion is when gas particles escape through tiny holes in
Effusion is when gas particles escape through tiny holes in
a container
a container

GRAHAM’S LAW
GRAHAM’S LAW
 √
√(Molar Mass
(Molar MassB
B/Molar Mass
/Molar MassA
A)
)
 The rates of effusion of two gases are
The rates of effusion of two gases are
inversely proportional to the square roots
inversely proportional to the square roots
of their molar masses
of their molar masses
 Use periodic table to get molar masses
Use periodic table to get molar masses

GRAHAM’S LAW
GRAHAM’S LAW
 What is the ratio of the speeds of Helium
What is the ratio of the speeds of Helium
compared to Oxygen?
compared to Oxygen?
 If Co
If Co2
2 has a speed of 22 m/s at 20°C, what is
has a speed of 22 m/s at 20°C, what is
the speed of HCl at the same temperature?
the speed of HCl at the same temperature?

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