1. Warm-Up 12/9/2016
Which represents the formula for Iron (III) Chromate?
A) Fe2(CrO4)3
B) Fe2(CrO4)2
C) Fe3(CrO4)2
D) Fe3(CrO4)3

2. Unit 5 Gas Laws and Kinetic Molecular Theory

3. Kinetic Molecular Theory(K.M.T)
The Kinetic Molecular Theory is used to describe the behavior of gases
The Theory describes the motion of the particles of a gas

4. Assumptions of the Kinetic Molecular Theory
1. Gases consist of large numbers of tiny particles
2. These particles are in rapid motion
they possess kinetic energy (energy of motion)

6. Assumptions Continued
3. All collisions the particles make between any substance are perfectly elastic collisions
Elastic Collisions is one in which there is not net loss of kinetic energy
4. The particles do NOT interact with each other
In other words, the particles do not attract or repel each other

7. Important Terms in Describing Gases
Devices Used to Measure Pressure:
1. Barometers-which is an instrument that is used to measure atmospheric pressure
2. Manometers-is an device employed to measure pressure inside of a container

8. Important Terms in Describing Gases
Gas Pressure: results from the numerous collisions of particles
[Pressure is equal to force divided by area]
P=F/A
When no particles are present, no collisions occur which creates a VACUUM

9. The following are possible units used for pressure: Pascal [Pa]
Units for pressure
The following are possible units used for pressure:
Pascal [Pa]
kiloPascal [kPa]
millimeter of mercury [mm Hg]
torr [torr]
atmosphere [atm]

10. Conversions Involving Volume
The official SI unit for volume is the kPa
Conversions Factors:
1 kPa = 1000 Pa
1 atm = kPa
1 atm = 760 mm Hg 1 atm = 760 torr

11. Example Problems
1. How many atm are in 600 kPa?
2. How many mm Hg are in kPa?

12. Factors that Affect Gases
Four factors affect gases:
1. Pressure
2. Temperature
3. Amount of Substance Present (mole)
4. Volume

13. How is Pressure effect Gases?
Adding more gas increases the pressure
Decreasing the volume that the gas occupies increases pressure

14. Temperature
Temperature is a measure of the average kinetic energy of particles of an object
Possible Temperature Units:
Celsius and Kelvin
K = °C

15. Values for STP are 1 atm pressure and 0 °C
Other Important Terms
Absolute Zero: as temperatures begin to approach this value, the motion of the particles slow down to a standstill
This value is -273 °C or 0 K
Standard Temperature and Pressure (STP): standard measurements used by scientists
Values for STP are 1 atm pressure and 0 °C

16. Temperature and Volume
For an increase in temperature, heat or energy must be added
When energy is added, the particles absorb the energy and begin moving more quickly
Therefore the particles spread out producing an increase in volume

17. Temperature and Volume
Temperature and Volume are directly related
Directly means that as one variable changes, the other variable changes in the same direction

18. Volume
Units for Volume:
m3, cm3, dm3, mL, L
Relationships:
1 mL = 1 cm3
1 dm3 = 1 L

19. Combined Gas Law
Charles and Boyle’s Laws can be combined together to yield a combined gas law
The Combined Gas Law allows for changes in volume, temperature, and pressure

20. Combined Gas Law
P1 * V1 T1 T2
P2 * V2 =

21. Variables in Combined Gas Laws
V1 = original volume
P1 = original pressure
T1 = original temperature (in K)
V2 = final volume
P2 = final pressure
T2 = final temperature (in K)

22. Example Problem #1
A helium balloon has a volume of 50.0 L at ° C and 820 mm Hg. What volume will it occupy at 650 mm Hg and 10°C?
Ans) 59.9 L

23. Example Problem #2
The volume of a gas is 27.5 mL at 22°C and 740 mm Hg pressure. What will be its volume at 15°C and 755 mm Hg?
Ans) 26.3 mL

24. Practice Problem # 3
A gas occupies a volume of 34.5 cm3 at 345 torr and 45ºC. What is the new pressure if the gas expands to a volume of 56.8 mL and temperature of 34ºC?
Answer = torr

25. Practice
A balloon indoors, where the temperature is 27° C, has a volume of 2.00 L. What will its volume be outdoors, where the temperature is -23°C?

26. Practice Question
If you were able to take a volleyball scuba diving with you, what would be its new volume if it started at the surface with a volume of 2.00 L, under a pressure of mmHg and a temperature of 20.0 ˚C ? On your dive you take it to a place where the pressure is 2943 mm Hg, and the temperature is 2.45 ˚C.