Gaseous state

Question 1

5 assumptions of the kinetic theory of gases

Answer 1

1. Gas particles have negligible volume compared to the volume of the container
2. The intermolecular forces of attraction between gas particles is negligible
3. Collisions between gas particles and the walls of the container are perfectly elastic
4. Gas particles are in constant random motion
5. The average kinetic energy is proportional to the absolute temp

Question 2

Partial pressure

Answer 2

In a mixture of gases, the pressure exerted by any individual gas on the sides of a container is known as the partial pressure of the gas

Question 3

Dalton’s law of partial pressures

Answer 3

Dalton’s law of partial pressure states that the total pressure of a mixture of gases is the sum of the partial pressures of the constituent gases

Question 4

Define mole in terms of Avogadro’s constant

Answer 4

One mole of a substance is the amount of substance that contains the same number of particles as there are atoms in 12g of the carbon-12 isotope

Question 5

Relative molecular mass

Answer 5

Relative molecular mass is the average mass of one mole of a substance relative to 1/12 the mass of one atom of carbon-12

Question 6

Conditions necessary for gases to approach ideal behaviour

Answer 6

low pressure and high temp

Question 7

Why do gases deviate from ideality at high pressure?

Answer 7

• the volume occupied by the gas is significant compared to the volume of the container
• attractive forces are not negligible as molecules are close together

Question 8

Why do gases deviate from ideality at low temp?

Answer 8

the molecules have lower kinetic energy so that their intermolecular forces become more significant

Question 9

How does deviation vary according to molecular size?

Answer 9

Deviation is greater for large, polar molecules with stronger intermolecular forces of attraction

Question 10

Boyle’s Law

Answer 10

The volume of a fixed mass of gas is inversely proportional to its pressure at constant temp (P1V1=P2V2)

Question 11

Charles’ Law

Answer 11

The volume of a fixed mass of gas is directly proportional to its absolute temp at constant pressure (V1/T1=V2/T2)

Question 12

Pressure Law

Answer 12

The pressure of a fixed mass of gas is directly proportional to its temp (in K) at constant volume (P1/T1=P2/T2)

Question 13

Ideal Gas eqn

Answer 13

PV=nRT

P in Pa
V in m3
T in K