The gas Laws
• What is a gas?
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–
–
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Small particles
Far apart
Constant linear motion
compressible
Avogadro’s Hypothesis
22.4 L of a gas (at STP) = 1 mole
Avogadro's Hypothesis: At the
same temperature and pressure,
equal volumes of different gases
will have the same number of
molecules.
AVOGADRO'S LAW : The
volume of a gas and the numbers
of molecules of that gas are
directly proportional at a fixed
temperature and pressure
Practice Problems
(select gas
stoichoimetry)
Avogadro’s
Hypothesis problems
• How many helium atoms are in a
4.00 liter balloon?
• 1.08 x 1023
Daltons law of partial pressure
• Pt= P1 + P2 + P3 …..
DALTON'S LAW OF PARTIAL
PRESSURES states that the total pressure
of a mixture of gases must be equal to the
sum of all the partial pressures of the
individual gases in the mixture.
Daltons law in action
• If a container is at 101.3 kPa, and contains
35 kPa of oxygen, and an unknown
amount of nitrogen, what is the pressure of
the nitrogen?
• Pt= P1 + P2 +
• 101.3 kPa = 35 kPa + Pnitrogen
• Pnitrogen =
Practice problems
Boyles law: Volume
and Pressure
• Demonstration
• At a constant
temperature, the
volume of a gas
varies inversely with
the pressure.
• P1V1=P2V2
Audible demonstration
Boyles gas law problems
Consider a helium balloon with a volume
of 3.0L at 101.3 kPa.
– If you let it go and it floats high into
the atmosphere where the pressure is
only 75 kPa, what will the volume be?
•4.0 Liters
•A burst balloon!
Tutorial
Charles’ law:
Volume and
temperatur
e
• An increase in
temperature results in
an increase on
volume
• Charles’ law (liquid
nitrogen)
• tutorial
Charles Gas law problems
• Consider a balloon with
a volume of 22.4 L at
273 K. What will be the
new volume if the
temperature increases
to 298 K?
• V2= V1T2 /T1
• V2 = (22.4L) (298K)/ (273K)
• 24.5 l
tutorial
Pressure and
temperature
Gay – Lussac’s Law:
for a fixed amount of gas (fixed
number of moles) at a fixed volume, the pressure is proportional to
the temperature
Tutorial
Animation
Gay – Lussac’s Law
Tutorial
• Consider a container with a volume of 22.4 L filled
with a gas at 1.00 atm at 273 K. What will be the new
pressure if the temperature increases to 298 K?
• p2 = 1.09 atm
Grahm’s law of effusion
• The rate of movement of a gas is inversely
related to the square root of the mass
• Simulation
• Practice problems
Ideal gas
• a gas is considered ideal when there is no
interaction between the molecules and
when collisions between the t molecules
and the container walls are elastic.
• Cool simulation
• Non ideal gases
• Tutorial