Ideal gases

Question 1

What is Avogadro’s constant?

Answer 1

It is the number of atoms present in 12 g of carbon 12

Question 2

What is a mole?

Answer 2

It is the amount of substance containing the same number of particles as in 12g of carbon 12

Question 3

What is an ideal gas?

Answer 3

It is a gas that obeys the ideal gas equation for all values of P, V and T.

Question 4

What is the ideal gas equation?

Answer 4

pV = nRT

Question 5

What are the conditions for the ideal gas equation to be valid?

Answer 5

1. Fixed amount of gas
2. Ideal gas

Question 6

What is Boyle’s law?

Answer 6

P ≈ 1/V

Hence pV = constant

Question 7

What is charles Law?

Answer 7

V ≈ T and hence V/T = constant

Question 8

Explain how molecular movement causes pressure with reference to the kinetic model of matter.

Answer 8

1. Molecules hit and rebound off the walls of the container
2. They change in momentum and this gives rise to force
3. many impulses averaged to give constant force and hence pressure

Question 9

What is the evidence for the random motion of particles?

Answer 9

Brownian motion

Observing the particles under a smoke cell under a microscope.

Question 10

What are the basic assumptions of the kinetic theory of gases?

Answer 10

1. The gas contains a large number of particles
2. Negligible intermolecular forces of attraction
3. Volume of particles negligible compared to container
4. Collisions between particles are perfectly elastic
5. No time spent in collisions
6. Average K.E is directly proportional to absolute temperature.

Question 11

What is mean square velocity?

Answer 11

It is the mean value of the square of all of the velocities of the molecules.

Question 12

Derive an expression for pressure of an ideal gas inside a cube with side length L.

Answer 12

Use change in momentum, time, and impulse.

Question 13

Find an expression for the kinetic energy of a molecule of an ideal gas.

Answer 13