A2 Unit 15 Ideal Gases

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Define Avogadro’s constant

Number of molecules in one mole of a substance

Define an ideal gas

Gas which obeys the relation pV ∝ T, where T is thermodynamic temperature

Describe Brownian motion

Particles move in straight lines in random directions

Describe how a gas causes pressure in a container

Gas particles collide with the sides of the container. The change in momentum causes a force to be exerted over a small area on the sides of the container. The sum of all these forces being exerted on small areas everywhere on the sides of the container causes pressure in the container.

Give Boyle’s Law

For a fixed mass of gas at constant temperature the pressure and volume are inversely proportional

Give Charles’s Law

For a fixed mass of gas at constant pressure the volume and absolute temperature are directly proportional

Give the Pressure Law

For a fixed mass of gas at constant volume the pressure and absolute temperature are directly proportional

Give the ideal gas equations

pV = nRT

pV = NkT

State the assumptions made for the kinetic model of gases

1. Gas contains a large number of particles moving at random that collide elastically with the walls and with each other

2. The forces between particles are negligible

3. The volume of the particles is negligible compared to the volume of the gas

4. The time of the collision by a particle with the container walls is negligible compared with the time between collisions

Define the Boltzmann constant

Gas constant per molecule

k = R/N_A

Define the root mean square speed of a gas

The square root of the average of the squares of the speeds of all molecules in a gas

c_r.m.s. = √<c²>