Chapter 7 - Liquids, Gases And Solids

Question 0

Explain Avogadro’s hypothesis

Answer 0

He suggested a proposal concerning the relationship between the amount of a gas and it’s volume. His hypothesis was that ‘equal volumes of gases at the same temperature and pressure contain equal numbers of particles’.
A standard molar volume has been defined as the volume of one mole of an ideal gas at 0C and 101.3 kPa (STP). Under STP conditions the value of the molar volume is 22.41 L mol^-1
The formula to calculate the amount of gas, in mole, from the volume of the gas, is
n = V
22.41

Question 1

Explain the assumptions of Kinetic Theory

Answer 1

• gases consist of tiny particles moving in rapid, random straight line motion until they collide with one another or the walls of its container
• Collisions between particles or with the walls of the container are perfectly elastic. There is no change in energy as a result of these collisions
• the size of the particles is negligible compared to the size of the container in which they are moving.
• Any attractive or repulsive force between the particles in negligible
• kinetic energy increases as temp. increases.

Question 2

List major ideas about Kinetic Energy

Answer 2

For a constant mass of a gas at a constant temperature, it’s volume decreases as it’s pressure increases
For a constant mass of a gas at a constant pressure, as it’s temp. increases, so does its volume, as it decreases, so does its volume.
Kelvin temp = Celsius temp + 273

Question 3

What is evaporation?

Answer 3

It is the change from a liquid to a gas at s temperature below the boiling point. Evaporation occurs at the surface of a liquid

Question 4

What is vapour pressure

Answer 4

It is the pressure exerted by a vapour in equilibrium with the liquid from which it was derived.
The vapour pressure of a liquid increases as it’s temp. does.
The larger the intermolecular forces between the molecules of a liquid, the lower it’s vapour pressure.

Question 5

What is boiling point

Answer 5

It is the change from a liquid to a gas at the boiling point. Boiling occurs through the liquid.
The boiling point is the temperature at which the vapour pressure of a liquid equals atmospheric pressure.