Chapter 7: Ideal Gases

Question 1

State Boyle’s law

Answer 1

The pressure exerted by a fixed mass of gas is inversely proportional to its volume provided temp. remains constant

Question 2

What’s the formula for Boyle’s and Charles’ combined laws

Answer 2

pV/T = constant

Question 3

Draw a graph for p against V

Answer 3

See page 92

Question 4

Draw a graph for p against 1/V

Answer 4

See page 92

Question 5

State the assumptions for the kinetic theory of gases

Answer 5

1. Gas contains v. large number of spherical particles
2. Forces between particles are negligible except during collisions
3. Volume of particles negligible compared to volume of gas
4. Particles move in straight line at constant velocity
5. Collisions are negligible length of time compared to time between collisions
6. All collisions (P->P and P->wall) are perfectly elastic - no k.e. lost during collisions

Question 6

Model for pressure

Answer 6

Arises from (elastic) collisions of particles with walls of container
More frequent/harder collisions increases pressure

Question 7

Model for temperature

Answer 7

Avg. k.e. of gas’ particles

Faster particles moves -> greater k.e. -> higher temp.

Question 8

Ideal gas equation for no. moles

Answer 8

pV = nRT

Question 9

Ideal gas equation for no. atoms

Answer 9

pV = NkT

Question 10

Relationship between k.e. and temp.

Answer 10

The mean translational k.e. of an atom of an ideal gas is directly proportional to the thermodynamic temp. of the gas

Question 11

Relationship between internal energy and temp. for a gas

Answer 11

It’s a gas so e.p.e. = 0 -> k.e. = internal energy

Internal energy directly proportional to thermodynamic temp.

Question 12

Draw a Maxwell-Boltzmann speed distribution

Answer 12

Page 99

Question 13

Describe k.e. and speed of molecules of gases in air

Answer 13

Air is a mix of several gases whose molecules have different masses
K.e. is the same for all -> all at same temp.
Speed is different -> molecules have different masses