Kinetic Theory

Question 1

What are some assumptions made when talking about an ideal gas?

Answer 1

› Collisions between molecules and container walls are perfectly elastic
› Intermolecular forces are negligible (except during collisions)
› Duration of collisions is negligible compared to the time between collisions
› Volume of molecules is negligible compared to volume of container
› Molecules have a random distribution and speed so a random distribution of energy

Question 2

What causes pressure?

Answer 2

› Caused by the molecules colliding and exerting a force on to the container walls
› Due to Newton’s third law, the container walls exert a force back on the molecules, causing pressure

Question 3

What is meant by Avogadro’s constant?

Answer 3

The number of molecules in one mole of a substance

Question 4

How is translational kinetic energy derived?

Answer 4

› Equate p=(1/3)(N/V)(m)(mean square speed) with pV=nRT
› Multiply by 3/2 to get into the form (1/2)(mv^2)
› For one mole, n=1 and N= Avogadro’s constant
› k = R / Avogadro’s constant