Mole fractions

In this article Paul Yates overcomes some common misconceptions and misunderstandings encountered when dealing with fraction,s including mole fractions. 

Gas properties

This PhET animation allows the link between the number of molecules of each gas in a gaseous mixture to be explored.

Should K_p have units?

Rod Beavon argues in this article why he thinks K_p shouldn't be given any units and why the values calculated using partial pressures in kPa are wrong.

Khan Academy video tutorials 

These tutorials cover the Ideal Gas Law and the calculation of partial pressures in a mixture of gases.