Kinetic Theory of Gases

Average Kinetic Energy

Equation contains three constants (3/2, R, NA) and only one variable, the temperature T.

Gas molecules are in constant, chaotic motion

They collide frequently with one another and with the container walls. Their velocities are constantly changing

Density of Gas

decrease in pressure = increase in density increase in temperature = decrease in density molar mass is directly proportional to molar mass

Effusion of Gases

depends on pressures of gases and the relative speed of their particles. At constant pressure, and temperature, the rate of effusion = square root of molar mass. At a given temperature and pressure, the rate of effusion of a gas, in moles, per unit time, is inversely proportional to the square root of its molar mass.

Average Kinetic Energy of Translational Motion

At a given temperature, molecules of different gases must all have the same average kinetic energy of translational motion. Average kinetic energy of a gas molecule is directly proportional to the temperature in Kelvins

Gas pressure is caused by the collision of molecules with the walls of the container

Pressure increase with energy and frequency of collisions

Pressure

The more molecules there are in a given volume, the greater the collision frequency and so the greater the pressure. Pressure is directly related to energy of collision (mass x u^2)

Collisions are elastic

There are no attractive forces that would tend to make molecules stick to one another or to the container walls.

Average speed

speed depends on both temperature and molar mass. Average speed is directly proportional to the square root of the absolute temperature, and inversely proportional to the square root of molar mass (MM). For two different gases A and B at the same temperature.

Gases are mostly empty space

the total volume of the molecules is negligibly small compared with that of the container to which they are confined