Title: Lesson 10 Ideal Gas Equation
Learning Objectives:
– Understand the ideal gas equation
– Complete a circus of short experiments to explore
the ideal gas equation
– Perform calculations using the ideal gas equation
Molar Volume of a Perfect Gas
We learnt about the molar volume of gases last lesson….how can
they be the same?
The distance between particles is much bigger than the size of the
particles….so particle size makes very little difference:
The blue particle is twice the size of the red particle, but the blue
particles are not taking up twice the amount of space.
10 units
10 units
In reality, the relative distance between the molecules is much much
greater than this.
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The Ideal Gas Equation
The volume a gas takes up is determined by:
Pressure
Temperature
Moles of gas
The value of the constant is directly proportional to the fixed mass of gas, or
the number of moles, n
This combines to form the ideal gas equation
PV = nRT
Where:
P = pressure in Pa
V = volume in m3
n = moles of gas
R = gas constant, 8.31 J K-1 mol-1, this appears in many places in chem
T = temperature in K
Calculating the Mr of gases
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© Boardworks Ltd 2009
Using the ideal gas equation
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© Boardworks Ltd 2009
Ideal Gas Assumptions
Particles occupy no volume
Particles have zero intermolecular forces
These are not always valid, particularly at:
Low temperature
High pressure
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Study the equation to make some
predictions:
PV = nRT
How would does temperature change if you decrease pressure
at fixed volume?
If you decrease pressure, temperature will decrease.
How would volume change if you heat something at fixed
pressure?
If you increase temperature, volume will increase.
How would pressure change if you decrease the volume at
fixed temperature?
If you decrease volume, pressure will increase.
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Exploring Ideal Gases
The best way to explore the behaviour of gases is to have
a little play.
Complete these four short experiments
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