1. Kinetic Molecular Theory (KMT)
Model that attempts to explain the behavior of an ideal gas
Ideal gas = high temperatures &/or low pressures
Even though real gases do not conform exactly to the 5 postulates, they are a useful first step in describing gas behavior.

2. (KMT)
Gases consist of tiny particles (atoms or molecules)
TRUE!

3. (but still a part of the theory b/c it’s almost true)
(KMT)
2. Gas particles are so small and so far apart that the volume of the particles themselves is negligible (zero).
the volume occupied by a gas consists mostly of empty space
(typically about 99.9% empty).
FALSE!
(but still a part of the theory b/c it’s almost true)

4. These collisions with the walls cause the PRESSURE exerted by the gas
3. Gas particles move randomly in all directions, traveling in straight lines.
A particle’s path is only changed by colliding with another particle or the sides of its container
*Gas molecules travel at very high speeds, about 6000 km/hr (~2700 mi/hr).
(KMT)
These collisions with the walls cause the
PRESSURE exerted by the gas
TRUE!

5. (but still a part of the theory b/c it’s almost true)
4. Gas particles are not attracted to or repelled by each other.
No attractive or repulsive forces between particles in an ideal gas
Gas particles’ collisions are perfectly elastic.
(KMT)
FALSE!
(but still a part of the theory b/c it’s almost true)

6. TRUE! (KMT) HOTTER COLDER
5. The higher the average temperature of the particles, the higher the kinetic energy.
Temperature is really a measure of the motions of the gas particles
HOTTER
COLDER
TRUE!

7. SIDE NOTE ... TEMPERATURE SCALES
Absolute temperature: T based on average particle speed; measured in Kelvin (K)
For this chapter, ALWAYS use Kelvin when doing calculations w/ temperature!!
Absolute zero (0 K): particles are not moving; there is no T below 0 K.
K = °C + 273

8. QUESTION #1 Ammonia gas occupies a volume of 450. mL
at 720. mm Hg. What volume will it occupy at
standard pressure?
Courtesy Christy Johannesson

9. V2 = P1V1 P2 426 mL ANSWER #1 BOYLE’S LAW V1 = 450. mL P1 = 720. mm Hg
P1V1 = P2V2
Courtesy Christy Johannesson

10. QUESTION #2 A gas at STP is cooled to -185°C.
What pressure in atmospheres will it have at this temperature?
Courtesy Christy Johannesson

11. ANSWER #2 P2 = P1T2 T1 0.32 atm GAY-LUSSAC’S LAW P1 = 1 atm T1 = 273 K
T2 = -185°C
= 88 K
P1 = P2 T1 T2
Courtesy Christy Johannesson

12. QUESTION #3 A 3.75 g helium occupies 3.8 L at -45°C.
What volume will it occupy at 45°C?
Courtesy Christy Johannesson

13. ANSWER #3 V2 = V1T2 T1 5.3 L CHARLES’S LAW
n = constant (mass doesn’t change)
V1 = 3.8 L
T1 = -45°C (228 K)
V2 = ?
T2 = 45°C (318 K)
V1 = V2 T1 T2
Courtesy Christy Johannesson

14. QUESTION #4 2.50 mol of a gas occupies 256 mL at 720 torr and 25°C.
How many moles of this gas would be present in a 105 mL container at STP?
Courtesy Christy Johannesson

15. n2 = P2V2n1T1 P1V1T2 1.18 mol ANSWER #4 n1 = 2.50 mol V1 = 256 mL
P1 = 720 torr
T1 = 25°C = 298 K
n2 =
V2 = 105 mL
P2 = 760. torr
T2 = 273 K
COMBINED
GAS LAW
n2 = P2V2n1T1
P1V1T2
1.18 mol
P1V1 = P2V2
n1T1
n2T2
Courtesy Christy Johannesson

16. QUESTION #5
How large would a kL weather balloon containing mol of gas become if you doubled the number of particles in the balloon?
Courtesy Christy Johannesson

17. ANSWER #5 V2 = V1n2 n1 7,900. L AVOGADRO’S LAW n1 = 15.05 mol
V1 = kL = 3,950 L
n2 = mol
V2 = ?
V1 = V2 n1 n2
Courtesy Christy Johannesson

18. QUESTION # 6 A gas occupies 125 mL at 125 atm. After being
heated to 75°C and depressurized to atm,
it occupies L. What was the original
temperature of the gas?
Courtesy Christy Johannesson

19. T1 = 544 K (271°C) ANSWER # 6 COMBINED GAS LAW P1V1 = P2V2 n1T1 n2T2
V1 = 125 mL
P1 = 125 atm
T2 = 75°C = 348 K
P2 = atm
V2 = L = 100. mL
T1 = ?
COMBINED
GAS LAW
P1V1 = P2V2
n1T n2T2
T1 = 544 K
(271°C)
Courtesy Christy Johannesson

20. QUESTION # 7
What is the mass of a 3.34 L sample of chlorine gas if the volume was determined at 37 oC and mm Hg?
Courtesy Christy Johannesson

21. ANSWER #7 PV = nRT n = PV RT P = 467.9 mmHg = .6157atm V = 3.34 L
n = ?? mol → ? g
T = 37 oC = 310 K
R = L ∙atm
mol ∙ K
IDEAL GAS LAW
PV = nRT
n = PV RT
n = mol
Courtesy Christy Johannesson

22. Question #8
Find the volume of hydrogen gas produced when 38.2 g of hydrochloric acid reacts with excess zinc at STP.

23. ANSWER #8 Gas Stoichiometry
Zn (s) HCl (aq)  ZnCl2 (aq) + H2 (g)‏
excess g HCl ?L

24. Question #9
Suppose you have a 1.00 L container of oxygen gas at atm and a 2.00 L container of nitrogen gas at 0.75 atm. 
If you transfer all of the oxygen to the container holding the nitrogen,
a) what pressure would the nitrogen exert?
b) what pressure would the oxygen exert?
c) what is the total pressure exerted by the mixture?

25. ANSWER #9 Dalton’s Law
Part A:  The nitrogen gas would exert the same pressure (its partial pressure)
       
Pressure exerted by the nitrogen gas = 0.75 atm
Part B: Use Boyle’s law to find the pressure of the oxygen gas (its partial pressure) after it’s been transferred into the nitrogen container
P1V1 = P2V2
P2 =   P1V1 =  1.05 atm   V2
Pressure exerted by the oxygen gas = 1.05 atm
Part C:  Use Dalton's Law of Partial Pressures to solve for the total pressure exerted by the mixture. 
                              
PTotal =  PN2 + PO2 = 0.75 atm atm = 1.80 atm