Unit 8- BEHAVIOR OF GASES.pptUnit 8- BEHAVIOR OF GASES.ppt

Unit 8- BEHAVIOR OF GASES.ppt

1. BEHAVIOR OF GASESBEHAVIOR OF GASES

2. PROPERTIES OF GASESPROPERTIES OF GASES
No definite shape/volumeNo definite shape/volume
Expands to fill its containerExpands 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
pressurepressure
Gases are easily compressed because of Gases are easily compressed because of
the space between the particles in a gasthe space between the particles in a gas

3. PROPERTIES OF A GASPROPERTIES OF A GAS
Factors Affecting Gas PressureFactors Affecting Gas Pressure
Amount of GasAmount of Gas
Increase amount, increase pressureIncrease amount, increase pressure
VolumeVolume
Reduce volume, increase pressureReduce volume, increase pressure
TemperatureTemperature
Increase temperature, increase pressureIncrease temperature, increase pressure
Relationship between pressure, Relationship between pressure,
temperature, and volume is explained temperature, and volume is explained
through the Gas Lawsthrough the Gas Laws

4. GAS LAWSGAS LAWS
Boyle’s LawBoyle’s Law
Charles’ LawCharles’ Law
Gay-Lussac’s LawGay-Lussac’s Law
Combined Gas LawCombined Gas Law
Ideal Gas LawIdeal Gas Law
Dalton’s Law of Partial PressureDalton’s Law of Partial Pressure
Graham’s LawGraham’s Law

6. BOYLE’S LAWBOYLE’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
decreasesdecreases
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 pressureinversely with pressure
As volume goes up, pressure goes downAs volume goes up, pressure goes down
As volume goes down, pressure goes upAs volume goes down, pressure goes up
PP
11VV
11 = P = P
22VV
22

7. BOYLE’S LAWBOYLE’S LAW
Real Life ExampleReal 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 increasespressure on the syringe increases
Mathematical Example 1:Mathematical Example 1:
PP
11 = 758 torr = 758 torr VV
11 = 5.0L = 5.0L P P
22
= ?= ? VV
22 = 3.5L = 3.5L

8. BOYLE’S LAWBOYLE’S LAW
Mathematical Example 2Mathematical Example 2
If 4.41 dmIf 4.41 dm
33
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?

9. CHARLES’ LAWCHARLES’ 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 constantpressure 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 constantpressure is kept constant
As volume goes up/down, temperature goes As volume goes up/down, temperature goes
up/downup/down

VV
11 = V = V
22
Temperature must be in Temperature must be in
Kelvin! TKelvin! T
11 T T
22

10. CHARLES’ LAWCHARLES’ LAW
Real Life ExampleReal 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)

11. CHARLES’ LAWCHARLES’ LAW
Mathematical Example 1Mathematical Example 1
VV
11 = 250mL T = 250mL T
11 = 300K = 300K V V
22 = =
321mL T321mL T
22 = ? = ?
Mathematical Example 2Mathematical Example 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?

12. GAY-LUSSAC’S LAWGAY-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 constantis 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
constantconstant
PP
11 = P = P
22Temperature must be in Kelvin! TTemperature must be in Kelvin! T
11
TT
22

13. GAY-LUSSAC’S LAWGAY-LUSSAC’S LAW
Real Life ExampleReal Life Example
TiresTires
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 tiresthe tires
Mathematical Example 1Mathematical Example 1
PP
11 = ? = ? TT
11 = 456K = 456K
P P
22 = 789mmHg = 789mmHgTT
22 = 326K = 326K

14. GAY-LUSSAC’S LAWGAY-LUSSAC’S LAW
Mathematical Example 2Mathematical Example 2
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?

15. COMBINED GAS LAWCOMBINED GAS LAW
Combines Boyle’s, Charles’, and Gay-Lussac’s Combines Boyle’s, Charles’, and Gay-Lussac’s
lawslaws
Describes the relationship among temperature, Describes the relationship among temperature,
pressure, and volume of an enclosed gaspressure, 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 constantIF and ONLY IF the amount of gas is constant

PP
11VV
11 = P = P
22VV
22
Temperature must be in Temperature must be in
Kelvin!Kelvin!
TT
11 T T
22

16. IDEAL GAS LAWIDEAL 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 EquationGas Equation
Modified version of the Combined Gas LawModified version of the Combined Gas Law
PV = nRTPV = nRT
n = number of molesn = number of moles
R = ideal gas constantR = 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)

17. IDEAL GAS LAWIDEAL GAS LAW
Mathematical Example 1Mathematical Example 1
What is the pressure in atm exerted by 0.5 What is the pressure in atm exerted by 0.5
moles of Nmoles of N
22 in a 10L container at 298 in a 10L container at 298
Kelvin?Kelvin?
Mathematical Example 2 Mathematical Example 2
What is the volume in liters of 0.250 moles What is the volume in liters of 0.250 moles
of Oof O
22 at 20°C and 0.974 atm? at 20°C and 0.974 atm?

18. IDEAL GAS LAWIDEAL GAS LAW
Mathematical Example 3Mathematical Example 3
What is the temperature of 76 grams of ClWhat is the temperature of 76 grams of Cl
22 in in
a 24L container at 890mmHg?a 24L container at 890mmHg?
Mathematical Example 4Mathematical Example 4
A deep underground cavern contains A deep underground cavern contains
2.24x102.24x10
66
L of CHL of CH
44 at a pressure of at a pressure of
1.50x101.50x10
33
kPa and a temperature of 315K. kPa and a temperature of 315K.
How many kilograms of CHHow many kilograms of CH
44 does the cavern does the cavern
contain?contain?

19. IDEAL vs. REAL GASESIDEAL vs. REAL GASES
Ideal gases follow the gas laws at all Ideal gases follow the gas laws at all
conditions of pressure and temperatureconditions 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 existdoesn’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
pressurepressure
Under other conditions, behave as an ideal Under other conditions, behave as an ideal
gas wouldgas would

20. DALTON’S LAWDALTON’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 gasessum 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 pressuremixture 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 gasescomponent of gases
PP
totaltotal = P = P
11 + P + P
22 + P + P
33 + … + …

21. DALTON’S LAWDALTON’S LAW
Mathematical Example 1Mathematical Example 1
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.

22. DALTON’S LAWDALTON’S LAW
Mathematical Example 2Mathematical Example 2
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?

23. GRAHAM’S LAWGRAHAM’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 massesof the inverted molar masses
The relative rate of diffusionThe 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 throughoutuniform throughout
Gases of lower molar mass diffuse and effuse faster Gases of lower molar mass diffuse and effuse faster
than gases of higher molar massthan 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 containera container

24. GRAHAM’S LAWGRAHAM’S LAW
√√(Molar Mass(Molar Mass
BB/Molar Mass/Molar Mass
AA))
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 massesUse periodic table to get molar masses

25. GRAHAM’S LAWGRAHAM’S LAW
Mathematical Example 1Mathematical Example 1
What is the ratio of the speeds of Helium What is the ratio of the speeds of Helium
compared to Oxygen?compared to Oxygen?
Mathematical Example 2Mathematical Example 2
If CoIf Co
22 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?