unit 4 ib notes - dr. g's chemistry · 2018-09-09 · unit 4 - ib notes. real vs. ideal gas...
TRANSCRIPT
Gas LawsUnit 4 - IB Notes
Real vs. Ideal Gas
• KMT describes IDEAL gases. • This works for most gases … mostly • REAL gases are different:
Electrostatic Attractions
Volume
Avogadro’s Law
Equal volumes of different gases at the same temperature and pressure contain the same number of moles of particles!
Ideal Gas Law…
1 mole of a gas = 22.4 L
P = pressure (atm, kPa, mm Hg) V = volume (L or dm3) n = # of moles of gas R = ideal gas constant T = temperature (K)
Ideal Gas Law…
PV = nRT
R = 0.0821 L atm mol-1 K-1 R = 8.314 dm3 kPa mol-1 K-1 R = 62.4 L mm Hg mol-1 K-1
Example Problems
Calculate the volume of 10.0 moles of He gas at a pressure of 300 kPa and 50.0 ˚C.
Example Problems
Calculate the volume of 1.00 mol of H2 at STP*.
*STP = 0.00 ˚C and 1.00 atm
Gas Law History
P
V
V1P1 = V2P2
Boyle’s Law
Gas Law History
Charles’s Law
V
T
V1 = V2 T1 T2
Temperature is ALWAYS in Kelvin!
Gas Law History
Guy-Lussac’s Law
P1 = P2 T1 T2
Temperature is ALWAYS in Kelvin!
P
T
Combined Gas Law…From your Reference Tables
P1V1 P2V2
T1 T2=
Combined Gas Law…From your Reference Tables
P1V1 P2V2
T1 T2=
Constant Temperature = Boyle’s Law Example: heat is not added to the system and system is not insulated.
Combined Gas Law…From your Reference Tables
P1V1 P2V2
T1 T2=
Constant Temperature = Boyle’s Law Example: heat is not added to the system and system is not insulated.
Constant Pressure = Charles’s Law Example: system is open to air
Combined Gas Law…From your Reference Tables
P1V1 P2V2
T1 T2=
Constant Temperature = Boyle’s Law Example: heat is not added to the system and system is not insulated.
Constant Pressure = Charles’s Law Example: system is open to air
Constant Volume = Gay-Lussac’s Law Example: system is enclosed in a non-expandable container (glass jar).
Dalton’s Law of Partial Pressures
The total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture.
1. number of moles of gas 2. size of container 3. temperature of mixture
Combined Gas Law
Combining the above three laws allows us to
calculate changes for systems in which volume,
pressure, and temperature are changing.
*again, temperature must be expressed in Kelvin
* Notice that when
• Temperature is constant, the equation becomes Boyle’s Law
o Example: heat is not added to the system and system is not insulated
• Pressure is constant, the equation becomes Charles’ Law
o Example: system is open to air
• Volume is constant, the equation becomes Gay-Lussac’s Law
o Example: system in enclosed in a non-expandable container such as a glass
jar
Dalton’s Law of Partial Pressures
Dalton’s Law states that: The total pressure of a mixture of gases is equal to the
sum of the pressures of all the gases in the mixture.
Ptotal = P1 + P2 + P3 + …
The partial pressure of the gas depends on
1. the number of moles of gas,
2. The size of the container
3. the temperature of the mixture
Example 1:
A mixture of oxygen, carbon dioxide, and nitrogen has a total pressure 0.97 atm.
What is the partial pressure of O2, if the partial pressure of CO2 is 0.70 atm and the
partial pressure of N2 is 0.12 atm?
Ptotal = P1 + P2 + P3 + …
Ptotal = Pnitrogen + P carbon dioxide + Poxygen
0.97 atm = 0.12 atm + 0.70 atm + X
X= 0.15 atm
Dalton - Examples
A mixture of oxygen, carbon dioxide, and nitrogen has a total pressure of 0.97 atm. What is the partial pressure of O2 if the partial pressure of CO2 is 0.70 atm and the partial pressure of N2 is 0.12 atm?
Combined Gas Law
Combining the above three laws allows us to
calculate changes for systems in which volume,
pressure, and temperature are changing.
*again, temperature must be expressed in Kelvin
* Notice that when
• Temperature is constant, the equation becomes Boyle’s Law
o Example: heat is not added to the system and system is not insulated
• Pressure is constant, the equation becomes Charles’ Law
o Example: system is open to air
• Volume is constant, the equation becomes Gay-Lussac’s Law
o Example: system in enclosed in a non-expandable container such as a glass
jar
Dalton’s Law of Partial Pressures
Dalton’s Law states that: The total pressure of a mixture of gases is equal to the
sum of the pressures of all the gases in the mixture.
Ptotal = P1 + P2 + P3 + …
The partial pressure of the gas depends on
1. the number of moles of gas,
2. The size of the container
3. the temperature of the mixture
Example 1:
A mixture of oxygen, carbon dioxide, and nitrogen has a total pressure 0.97 atm.
What is the partial pressure of O2, if the partial pressure of CO2 is 0.70 atm and the
partial pressure of N2 is 0.12 atm?
Ptotal = P1 + P2 + P3 + …
Ptotal = Pnitrogen + P carbon dioxide + Poxygen
0.97 atm = 0.12 atm + 0.70 atm + X
X= 0.15 atm
Dalton - Water Vapor
Particularly useful when working in the lab, collecting gas over water. There is always some water vapor in the air. Must take into consideration the pressure that water vapor exerts on the total pressure.
• The total pressure equals the pressure of the water vapor + the pressure of the gas.
Dalton’s Law is particularly useful when you are working in the lab and have
collected gas over water. Because there is always some water vapor in the air, you
must take into consideration the pressure that water vapor exerts on the total pressure.
the total pressure equals the pressure of the water vapor + the pressure of the gas.
Ptotal = Pgas + P water vapor
Because water vapor pressure varies with temperature, you must make sure to take
that into consideration. Many sources have tables of water vapor pressure at various
temperatures.
Temperature
(°C)
Vapour
pressure
(kPa)
0 0.6
3 0.8
5 0.9
8 1.1
10 1.2
12 1.4
14 1.6
16 1.8
18 2.1
19 2.2
20 2.3
21 2.5
22 2.6
23 2.8
24 3.0
25 3.2
26 3.4
27 3.6
28 3.8
29 4.0
30 4.2
32 4.8
35 5.6
40 7.4
50 12.3
60 19.9
70 31.2
80 47.3
90 70.1
100 101.3
Example:
Hydrogen gas is collected over water at a total pressure of 95.0 kPa and a temperature
of 25 °C. What is the partial pressure of hydrogen gas?
According to the table the vapor pressure of water at 25°C is 3.2 kPa.
Ptotal = Pgas + P water vapor
95.0 kPa = X + 3.2 kPa
X = 91.8 kPa
Dalton - Water Vapor
Dalton’s Law is particularly useful when you are working in the lab and have
collected gas over water. Because there is always some water vapor in the air, you
must take into consideration the pressure that water vapor exerts on the total pressure.
the total pressure equals the pressure of the water vapor + the pressure of the gas.
Ptotal = Pgas + P water vapor
Because water vapor pressure varies with temperature, you must make sure to take
that into consideration. Many sources have tables of water vapor pressure at various
temperatures.
Temperature
(°C)
Vapour
pressure
(kPa)
0 0.6
3 0.8
5 0.9
8 1.1
10 1.2
12 1.4
14 1.6
16 1.8
18 2.1
19 2.2
20 2.3
21 2.5
22 2.6
23 2.8
24 3.0
25 3.2
26 3.4
27 3.6
28 3.8
29 4.0
30 4.2
32 4.8
35 5.6
40 7.4
50 12.3
60 19.9
70 31.2
80 47.3
90 70.1
100 101.3
Example:
Hydrogen gas is collected over water at a total pressure of 95.0 kPa and a temperature
of 25 °C. What is the partial pressure of hydrogen gas?
According to the table the vapor pressure of water at 25°C is 3.2 kPa.
Ptotal = Pgas + P water vapor
95.0 kPa = X + 3.2 kPa
X = 91.8 kPa
Tables provided for VP @ various temperatures.
Dalton - Water Vapor
Dalton’s Law is particularly useful when you are working in the lab and have
collected gas over water. Because there is always some water vapor in the air, you
must take into consideration the pressure that water vapor exerts on the total pressure.
the total pressure equals the pressure of the water vapor + the pressure of the gas.
Ptotal = Pgas + P water vapor
Because water vapor pressure varies with temperature, you must make sure to take
that into consideration. Many sources have tables of water vapor pressure at various
temperatures.
Temperature
(°C)
Vapour
pressure
(kPa)
0 0.6
3 0.8
5 0.9
8 1.1
10 1.2
12 1.4
14 1.6
16 1.8
18 2.1
19 2.2
20 2.3
21 2.5
22 2.6
23 2.8
24 3.0
25 3.2
26 3.4
27 3.6
28 3.8
29 4.0
30 4.2
32 4.8
35 5.6
40 7.4
50 12.3
60 19.9
70 31.2
80 47.3
90 70.1
100 101.3
Example:
Hydrogen gas is collected over water at a total pressure of 95.0 kPa and a temperature
of 25 °C. What is the partial pressure of hydrogen gas?
According to the table the vapor pressure of water at 25°C is 3.2 kPa.
Ptotal = Pgas + P water vapor
95.0 kPa = X + 3.2 kPa
X = 91.8 kPa
Hydrogen gas is collected over water at a total pressure of 95.0 kPa and a temperature of 25˚C. What is the partial pressure of the hydrogen gas?
Ptotal = Pgas + Pwater vapor
95 kPa = X + 3.2 kPa
X = 91.8 kPa
Maxwell-Boltzmann Distribution• Distribution of the kinetic energy of particles. • # of particles = constant • Higher temperature = higher kinetic energy of particles
Maxwell-Boltzmann Simulation
Maxwell-Boltzmann Video Explanation