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Gases Dr. Ron Rusay Summer 2004 © Copyright 2004 R.J. Rusay.

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Presentation on theme: "Gases Dr. Ron Rusay Summer 2004 © Copyright 2004 R.J. Rusay."— Presentation transcript:

1 Gases Dr. Ron Rusay Summer 2004 © Copyright 2004 R.J. Rusay

2 Gases

3 Gases: Pressure, Mass, Volume, Temperature

4 Pressure Pressure is equal to force/unit area
SI units = Newton/meter2 = 1 Pascal (Pa) 1 standard atmosphere = 101,325 Pa 1 standard atmosphere = 1 atm = 29.92 inches of Hg 34 feet of H2O

5 Measuring Atmospheric Pressure Toricellian Barometer
1 standard atmosphere 1 atm = mm Hg 29.92 inches of Hg 34 feet of H2O

6 Pressure & Volume Boyle’s Law*

7 Changing Volume @ constant temperature P  V  P  V ?

8 Pressure & Volume Boyle’s Law*

9 Boyle’s Law ** Pressure  Volume = Constant (T = constant)
V  1/P (T = constant) (*Holds precisely only at very low pressures.)

10 Changing Volume **

11 Pressure vs. Volume

12 Ideal Gases Real vs. “Ideal” Definition: A gas that strictly obeys Boyle’s Law is called an ideal gas.

13 Temperature & Volume (@ constant pressure)

14 Temperature & Volume 77 K = ? oC

15 Temperature & Volume What happened in the balloon on a molecular level?

16 Charles’s Law ** The volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin. V = T (P = constant) = a proportionality constant

17 Temperature and Volume (@ constant P)

18 Pressure vs. Temperature (@ constant V)

19 Pressure vs. Temperature (@ constant V)
“Gay Lussac’s Law”

20 Vapor Pressure vs. Temperature solid  liquid  gas

21 Pressure, Volume & Temperature
(PV&T)

22 Molecular Motion / Theory
The Meaning of Temperature Temperature (Kelvin) is an index of the random motions of gas particles (higher T means greater motion.)

23

24 Standard Temperature and Pressure
“STP” P = T =

25 Avogadro’s Law For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas (at low pressures). V = n = proportionality constant V = volume of the gas n = number of moles of gas

26 Volume vs. n (moles of a gas)

27 Ideal Gas Law ** An equation of state for a gas.
“state” is the condition of the gas at a given time.

28 Ideal Gas Law ** PV = nRT Holds closely at P < 1 atm
R = proportionality constant = L atm  mol P = V = n = T = Holds closely at P < 1 atm

29 Molar Volume at Standard Temperature and Pressure
“STP” P = 1 atmosphere T = C The molar volume of an ideal gas is _____ liters at STP

30 Dalton’s Law of Partial Pressures **
For a mixture of gases in a container, (P constant V &T) PTotal = P1 + P2 + P


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