Dispatch Draw a picture of a gas in a container. Then answer the following questions: 1. What sort of path do the molecules travel in? 2. Do they all move at the same speed? 3. When temperature increases, what happens to the motion of the

1
DispatchDraw a picture of a gas in a container.
Then answer the following questions1. What
sort of path do the molecules travel in?2. Do
they all move at the same speed?3. When
temperature increases, what happens to the motion
of the particles?4. What happens when they
collide with the walls of the container?5. Why
is it possible to compress a gas?6. How does a
gas exert pressure?
2
Kinetic Theory of GasesBoyles Law,
Charless LawGay-Lussacs Law, Avogadros Law
3
Pressure of a Gas Depends on

• Number of molecules
• Volume in which they are contained
• Average kinetic energy of molecules

4
Boyles Law

• If the amount and temperature of a gas remain
  constant, the pressure exerted by the gas varies
  inversely with the volume.
• P ? 1/V or PV k

5
Applying Boyles Law P1V1 P2V2

• If some oxygen gas collected at 760 mm Hg is
  allowed to expand from 5.0 L to 10.0 L without
  changing the temperature, what pressure will the
  oxygen gas exert?

380 mm Hg
6
Charless Law

• The volume of a quantity of gas, held at a
  constant pressure, varies directly with the
  Kelvin temperature.
• V ? T or V kT

7
Applying Charles LawV1/T1 V2/T2

• A 225 mL volume of gas is collected at 58.0 oC.
  What volume would this sample of gas occupy at
  standard temperature, assuming pressure remains
  constant.

186 mL
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Combining Boyles and Charles Laws
The volume of a gas measured at 755 mm Hg and
23.0 oC is 455 mL. What is the volume of the gas
at STP?

• P1V1 P2V2
• T1 T2

417 mL
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Sample Problem

• At STP, the volume of a gas is 325 mL. What
  volume does it occupy at 20.0 oC and 756 mm Hg?

351 mL
10
Sample Problem

• A gas occupies a volume of 245 mL at 30.0 oC and
  746 mm Hg. Assuming no change in pressure, at
  what temperature will the gas occupy a volume of
  490. mL?

606 K
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Sample problem

• A chemist collects 8.00 mL of gas at STP. If
  the temperature remains constant, at what
  pressure will the gas volume be reduced to 4.00
  mL?

1520 mm Hg
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Gay-Lussacs Law

• The pressure of a quantity of gas, held at a
  constant volume, varies directly with the Kelvin
  temperature.
• P ? T or P kT

13
Avogadros Law

• The volume of a quantity of gas, held at a
  constant temperature and pressure, varies
  directly with the number of moles.
• V ? n or V kn