Gases

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Chapter 11

• Gases

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Other units for Pressure include atmospheres
(atm), millimeters of mercury (mmHg), Torr
(torr), pounds per square inch (psi),
kilopascals (kPa)
3
Atmospheric Pressure
1 atm 760 mm Hg 760 torr 101,325 Pa
101.325 kPa
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Measuring Gas PressureBarometer
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Manometers
Units must be the same usually mmHg
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Daltons Law of Partial Pressures

• PT P1 P2 P3

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• Gases collected by water displacement
• Patm Pgas Pwater

Pwater is the vapor pressure of the water at a
certain temperature
Pgas Pwater
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Gas Laws

• Laws that describe the behavior of gases under
  different atmospheric conditions
• Four governing quantities
• Pressure
• Temperature
• Volume
• Amount

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Boyles Law The volume of a gas is inversely
proportional to the pressure on the gas at
constant temperature and amount.
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Charles Law The volume of a gas is directly
proportional to the temperature of the gas at
constant pressure and amount.
TEMPERATURE MUST BE IN KELVIN !!!!!
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Gay-Lussacs Law The pressure of a gas is
directly proportional to the temperature of a gas
with constant volume and amount.
TEMPERATURE MUST BE IN KELVIN !!!!!
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Boyle Charles Gay-Lussac The Combined Gas
Law
TEMPERATURE MUST BE IN KELVIN !!!!!
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• Gay-Lussacs Law of Combining Volumes When
  gases react, the volumes consumed and produced,
  measured at the same temperature and pressure,
  are in ratios of small whole numbers.

Hydrogen gas Oxygen gas Water vapor2 dm3
1dm3 2 dm3 Hydrogen gas Nitrogen gas
Ammonia gas3 dm3 1 dm3 2 dm3
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• Avogadros Law - Equal volumes of all gases at
  the same temperature and pressure contain the
  same number of molecules.

Standard Molar Volume of a Gas _at_ STP 22.4 L/mol
STP Standard Temperature and Pressure 1 atm
273 K
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Ideal Gas Law
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Grahms Law of Effusion
The escape of a gas through a tiny pore or
pinhole in its container is called EFFUSION.
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Homework

• Pages 390-393
• Numbers 9,10,11,18,19,20,21,22,23,24,26,28,33
• 38,41,42,44,46,48,52,58