Gas Laws

1
Chapter 5

• Gas Laws

2
Scuba Diving
3
Dive Belize
4
Air

• The atmosphere is

5
Diving Issues

• Nitrogen Narcosis
• Nitrogen narcosis is a condition that occurs in
  divers breathing compressed air. When divers go
  below depths of approximately 100 ft, increase in
  the partial pressure of nitrogen produces an
  altered mental state similar to alcohol
  intoxication.

6
The Bends

• Decompression sickness
• nitrogen from the air will dissolve in the water
  in his or her body. If the diver were to swim
  quickly to the surface, it is just like uncorking
  a bottle of soda -- the gas is released. This can
  cause a very painful condition, and it is
  sometimes fatal.

7
Increased pressure

• The pressure on divers increases by one
  atmosphere for every 33 feet of depth
• At 100 feet, some people say it is difficult to
  breathe

8
Decompression

• If divers do not decompress as they surface, they
  can develop the bends.
• Stops at various intervals as they rise to the
  surface, sometimes for 15 to 20 minutes or more.

9
Pressure

• Defined as the force per area
• Equation

10
How is pressure measured?

• Barometers
• Manometers p 123, fig 5.2
• Units

11
Gas Properties

• The physical volume of the molecules is
  negligible compared to the container

12
Gas Properties

• Average kinetic energy is related to the absolute
  temperature

13
The Gas Laws

• Boyles
• Charles
• Guy-Lussacs
• Avogadros
• Combined

• Ideal
• Molecular mass
• Daltons partial pressures

14
Boyles

• Relates pressure and volume
• Equation
• Temperature and number of molecules fixed

15
Charles

• Relates volume and temperature
• Equation
• Pressure and number of molecules fixed

16
Guy_Lussacs

• Relates Pressure and Temperature
• Equation
• P/T Constant
• Volume and number of molecules fixed

17
Avogadros

• Relates number of molecules and volume
• Equation
• V/n constant
• Pressure and temp are fixed

18
Combined

• Relates P, V, and T
• Equation
• PV/T constant
• Number of molecules is fixed

19
Ideal Gas Law

• Combines all of the above
• Equation
• Use Standard Temperature and Pressure,

20
Molecular Mass

• Determine the molar mass of a gas
• n g/M
• n PV/RT
• g/M PV/RT
• M gRT/PV

21
Dalton and Partial Pressure

• Ptotal P1 P2

22
Henrys Law

• Relates solubility and pressure
• Equation

Volume gas dissolved
CH x Pg

Volume of liquid
23
Practice

• What is the volume of 2.40 moles of O2 under a
  pressure of 5.00 atm at a temperature of 755 K?