Unit 8 - BEHAVIOR OF GASES
Unit 8 - BEHAVIOR OF GASES
Unit 8 - BEHAVIOR OF GASES
Unit 8
Chemistry
Langley
Boyle’s Law
Charles’ Law
Gay-Lussac’s Law
Combined Gas Law
Ideal Gas Law
Dalton’s Law of Partial Pressure
Graham’s Law
BOYLE’S LAW
Mathematical Example 2
If 4.41 dm3 of nitrogen gas are collected at a
pressure of 94.2 kPa, what will the volume
be for this gas at standard pressure if the
temperature does not change?
CHARLES’ LAW
As the temperature of an enclosed gas
increases, the volume increases, if the
pressure is constant
The volume of a fixed mass of gas is directly
proportional to its Kelvin temperature if the
pressure is kept constant
As volume goes up/down, temperature goes
up/down
V1 = V2
Temperature must be in
Kelvin! T1 T2
CHARLES’ LAW
Real Life Example
Balloon Lab-As the temperature of the water
is increased, the volume of the balloon is
increased.
Coke Can-Fill a coke can with a small
amount of water, as you heat the water
inside to near boiling, immediately invert the
coke can into ice-cold water so the coke can
is experiencing a dramatic drop in
temperature, volume of can will decrease
(can will crush in on itself)
CHARLES’ LAW
Mathematical Example 1
V1 = 250mL T1 = 300K V2
= 321mL T2 = ?
Mathematical Example 2
With a constant pressure, the volume of a
gas is increased from 15.0L to 32.0L. If the
new temperature is 20.0°C, what was the
original temperature?
GAY-LUSSAC’S LAW
As the temperature of an enclosed gas
increases, the pressure increases, if the
volume is constant
The pressure of a gas is directly proportional to
the Kelvin temperature if the volume remains
constant
P1 = P2
Temperature must be in
Kelvin! T1 T2
GAY-LUSSAC’S LAW
Mathematical Example 2
The pressure in a tire is 1.8 atm at 20°C.
After a 200 mile trip, the pressure reading for
the tire is 1.9 atm. What is the temperature
inside the tire at that new pressure?
COMBINED GAS LAW
Combines Boyle’s, Charles’, and Gay-Lussac’s
laws
Describes the relationship among temperature,
pressure, and volume of an enclosed gas
Allows you to perform calculation for situations
IF and ONLY IF the amount of gas is constant
P1V1 = P2V2
Temperature must be in
Kelvin!
T1 T2
IDEAL GAS LAW
When you need to account for the number of
moles of gas in addition to pressure,
temperature, and volume, you will use the Ideal
Gas Equation
Modified version of the Combined Gas Law
PV = nRT
n = number of moles
R = ideal gas constant
0.08206 (L-atm/mol-K)
62.4 (L-mmHg/mol-K)
8.314 (L-kPa/mol-K)
IDEAL GAS LAW
Mathematical Example 1
What is the pressure in atm exerted by 0.5
moles of N2 in a 10L container at 298
Kelvin?
Mathematical Example 2
What is the volume in liters of 0.250 moles
of O2 at 20°C and 0.974 atm?
IDEAL GAS LAW
Mathematical Example 3
What is the temperature of 76 grams of Cl 2
in a 24L container at 890mmHg?
Mathematical Example 4
A deep underground cavern contains
2.24x106L of CH4 at a pressure of
1.50x103kPa and a temperature of 315K.
How many kilograms of CH4 does the cavern
contain?
IDEAL vs. REAL GASES
Ideal gases follow the gas laws at all
conditions of pressure and temperature
Conforms exactly to the all the assumptions
of the kinetic theory (no volume, no particle
attraction)doesn’t exist
Real gases differ mostly from an ideal
gas at low temperature and high
pressure
Under other conditions, behave as an ideal
gas would
DALTON’S LAW
In a mixture of gases, the total pressure is the
sum of the partial pressure of the gases
Partial pressure is the contribution each gas in a
mixture makes to the total pressure
At constant volume and temperature, the total
pressure exerted by a mixture of gases is
equal to the sum of the partial pressures of the
component of gases
Ptotal = P1 + P2 + P3 + …
DALTON’S LAW
Mathematical Example 1
In a container there are 4 gases with the
following pressures: Gas 1-2.5 atm, Gas 2-
1.9 atm, Gas 3-798 mmHg, Gas 4-2.1 atm;
find the total pressure in the container.
DALTON’S LAW
Mathematical Example 2
In a sample of HCl gas, the pressure of the
gas is found to be 0.87 atm. If hydrogen
makes up 34% of the gas, what is the
pressure of the hydrogen?
GRAHAM’S LAW
The ratio of the speeds of two gases at the
same temperature is equal to the square root
of the inverted molar masses
The relative rate of diffusion
Diffusion is the tendency of molecules to move
toward areas of lower concentration to areas of
higher concentration until the concentration is
uniform throughout
Gases of lower molar mass diffuse and effuse faster
than gases of higher molar mass
Effusion is when gas particles escape through tiny holes in
a container
GRAHAM’S LAW
Mathematical Example 1
What is the ratio of the speeds of Helium
compared to Oxygen?
Mathematical Example 2
If Co2 has a speed of 22 m/s at 20°C, what is
the speed of HCl at the same temperature?