What is the difference between the partial pressure and concentration?

1 Answer
Feb 19, 2016

Partial pressure is proportional to concentration.


Look at the Ideal Gas Law: PV = nRT. We can rearrange this equation to give: n/V = P/RT. The units for n/V are moles per Liter, ie. concentration!

So, any time you know the pressure contributed by a particular gas that is part of a gas mixture, you can calculate it's concentration. For example, if two gases have a combined pressure of 1 atmosphere, and the mixture is composed of 0.2 moles of oxygen and 0.8 moles of neon, then, 20% of the gas pressure is due to oxygen, and 80% is due to neon.

If oxygen has a partial pressure of 0.2 atm, and neon has a partial pressure of 0.8 atm, and you'd like to know, for example the concentration of neon when the temperature is 325K, then:

n/V = #(0.8 atm)/((0.0821 L*atm)/(mol*K)*350K# = 0.0278 m/L