The Ideal Gas Equation

Question 1

The kinetic theory of gases states that

Answer 1

molecules in gases are constantly moving

Question 2

the kinetic theory of gas suggests that

talkabout volume , how they move,attraction, energy,temp

Answer 2

That gas molecules are moving very fast and randomly

That molecules hardly have any volume

That gas molecules do not attract or repel each other (no intermolecular forces)

No kinetic energy is lost when the gas molecules collide with each other (elastic collisions)

The temperature of the gas is related to the average kinetic energy of the molecules

Question 3

Gases that follow the kinetic theory of gases are called

However, in reality gases do not fit this description exactly but may come very close and are called ………

Answer 3

ideal gases

real gases

Question 4

Ideal gases
The volume that an ideal gas occupies depends on:

Answer 4

Its pressure
Its temperature

Question 5

Why is volume directy proportional to temp at a constant pressure

Answer 5

When a gas is heated (at constant pressure) the particles gain more kinetic energy and undergo more frequent collisions with the container wall

To keep the pressure constant, the molecules must get further apart and therefore the volume increases

The volume is therefore directly proportional to the temperature (at constant pressure)

Question 6

Limitations of the ideal gas law

Answer 6

At very low temperatures and high pressures real gases do not obey the
kinetic theory as under these conditions:
Molecules are close to each other

There are instantaneous dipole- induced dipole or permanent dipole- permanent dipole forces between the molecules

These attractive forces pull the molecules away from the container wall

The volume of the molecules is not negligible

Question 7

Real gases therefore do not obey the following kinetic theory assumptions at …….. temperatures and ….. pressures:

and why is this

Answer 7

low
high

There is zero attraction between molecules (due to attractive forces, the pressure is lower than expected for an ideal gas)

The volume of the gas molecules can be ignored (volume of the gas is smaller than expected for an ideal gas)

Question 9

gas constant value

Answer 9

r= gas constant (8.31JK-1 mol-1)

Question 10

Exam Tip
To calculate the temperature in Kelvin,

Answer 10

add 273 to the Celsius temperature - e.g. 100 oC is 373 Kelvin.

You must be able to rearrange the ideal gas equation to work out all parts of it.

The units are incredibly important in this equation - make sure you know what units you should use, and do the necessary conversions when doing your calculations!