AIChapter 14 Gas Laws.notebook
March 22, 2012
Chemistry AI Chapter 14
A. Gas Pressure (14.1)
Behavior of Gases
1. Amount of gas As you increase the number of gas particles inside a raft, the pressure increases because the particles strike the inside walls of the container more often. If you double the number of particles, the pressure doubles. See page 415; Fig. 14.4 The mass also increases. This is a direct relationship.
Aug 1410:48 AM
B. Gas Laws (14.2)
1. Boyle’s Law In 1662 Robert Boyle proposed a law stating that for a given mass of gas at a constant temperature, the volume of the gas varies inversely with pressure. (ex. if the temperature remains the same, as the volume of a gas doubles, the pressure decreases by onehalf) See page 416; Fig. 14.6 This is an inverse relationship.
Aug 1410:48 AM
1
AIChapter 14 Gas Laws.notebook
March 22, 2012
a. Graph
See page 418; Fig.14.8
b. Equation
P1V1 = P2V2
Problems page 419; 7, 8 page 419
Aug 1410:48 AM
2. Charles’s Law page 421
In 1787 Jacques Charles proposed a law stating that for a given mass of gas at a constant pressure, the volume of the gas is directly proportional with its Kelvin temperature.
(ex. if the pressure remains the same, as the volume of a gas doubles, the temperature also doubles) See page 420; Fig. 14.9
This is a direct relationship.
Aug 1410:48 AM
2
AIChapter 14 Gas Laws.notebook
March 22, 2012
a. Graph
See page 420; Fig.14.10
b. Equation
V1 = V2 T1 T2
Problems page 421; 9, 10
3. GayLussac’s Law In 1802 Joseph GayLussac proposed a law stating that for a given mass of gas at a constant volume, the pressure of the gas is directly page 422 proportional to its Kelvin temperature.
Aug 1410:48 AM
(ex. if the volume remains the same, as the pressure of a gas doubles, the temperature also doubles) See page 422; Fig. 14.11
This is a direct relationship.
a. Graph
Draw it
b. Equation
P1 = P2 T1 T2
Problems page 423; 11, 12
Aug 1410:48 AM
3
AIChapter 14 Gas Laws.notebook
4. Combined Gas Law
March 22, 2012
A gas law that combines Boyle’s, Charles’s, and GayLussac’s laws.
The law provides a means to do calculations for situations in which only the amount of gas is constant.
a. Equation
P1V1 = P2V2 T1 T2
Problems page 424; 13, 14
Aug 1410:48 AM
5. Ideal Gas Law
The combined gas law assumes a constant amount of gas. (Constant moles) The ideal gas law is used to calculate the number of moles of a gas in a fixed volume at a known temperature and pressure.
The volume of a gas at a fixed temperature and pressure is directly proportional to the number of gas particles. The number of gas particles is related to moles. So moles can be substituted for number of gas particles.
Aug 1410:48 AM
4
AIChapter 14 Gas Laws.notebook
a. Equation
March 22, 2012
P1V1 = P2V2 T1n1 T2 n2
Where n= #moles
If we substitute the conditions for STP for one side then:
(101.3kPa)(22.4L) = P2V2 (273K)(1 mole) T2 n2
8.31(kPa)(L) = P2V2 (K)(mole) T2 n2 b. Ideal gas R=8.31(kPa * L) constant (R) (K*mole)
Aug 1410:48 AM
Substitution of R into the ideal gas law equation gives:
PV=nRT R=8.31(kPa * L) (K*mole)
(Note: when solving these problems all units must match R)
Problems page 427; 23, 24
All of the above equations assume that gases are ideal at all pressures and temperatures.
Aug 1410:48 AM
5
AIChapter 14 Gas Laws.notebook
March 22, 2012
This means that the gas particles follow the assumptions of the kinetic theory and have no volume and no attractive forces. 6. Real vs. Ideal gases
Ideal gases do not exist. However, at many conditions of pressure and temperature, real gases behave like ideal gases.
Real gases differ most from ideal gases at low temperatures and high pressures.
Aug 1410:48 AM
At low temperatures and high pressures real gases do have attractive forces causing them to condense and sometimes solidify. So their actual volume is less than expected for an ideal gas.
At high pressures real gas particles do have volume so their total volume is greater than an ideal gas.
See page 429; Fig. 14.15
Aug 1410:48 AM
6
AIChapter 14 Gas Laws.notebook
March 22, 2012
At constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each individual gas.
7. Dalton’s Law of Ptotal = P1 + P2 + P3 + ….. partial pressures page 432
See page 432; Table 14.1
The proportionate pressure (% contribution) exerted by each gas does not change with a change in temperature, pressure or volume.
Aug 1410:48 AM
Ex. oxygen Partial P Total P %P Sea Level 21.22kPa 101.3kPa 21 Mt. Everest 7.1 kPa 34.0kPa 21
Oxygen still make up 21% of the pressure even though its partial; pressure has been reduced.
Page 434; Prob. 31, 32
Aug 1410:48 AM
7
Attachments
14.Dalton problems 14.6.pdf 14.aerosol can.pdf 14.Bolye problems14.1.pdf 14.boyle's law 14.6.pdf 14.figure14.4 number of particles.pdf 14.Graph Boyle 14.8.pdf 14.Charles figure14.9.pdf 14.Charles graph14.10.pdf 14.Charles problems 14.2.pdf 14.Lussac 14.7.pdf 14.Lussac problems 14.3.pdf 14.Combined gas problems 14.4.pdf 14.Ideal gas problems 14.5.pdf 14.Real vs ideal 14.15.pdf 14.composition of air table 14.1.pdf 14.Dalton partial pressure 14.16.pdf