View Single Post
Old May 23rd 2009, 03:57 PM   #2
Super Moderator
Join Date: May 2009
Location: Montréal, QC
Posts: 76
Sodapop is on a distinguished road
I. Ideal gas law explanation
Three important factors influence the state of a gas: its pressure, its volume and its temperature. This law is a good approximation to the many possible behaviors of gases under certain restricted conditions. The form of the equation is the following:

pV = nRT
p = pressure of the gas
V = volume of the gas
n = amount of substance (most of the time expressed in moles)
R = ideal gas constant (0.08206 L atm mol^(-1) K^(-1))
T = absolute temperature (usually in Kelvin, where 273 K = 0°C)

As we all know, a formula has to posses the basic equilibrium found in any equality. In this case, the pressure of the gas multiplied by the volume of the gas gives us the numbers of moles multiplied by the constant R and the temperature. Simple algebra can be used to find the unknown or missing variable in our equation.

Please note: Always remember to convert your volume into L (litres), your temperature into K (Kelvin) and your atomspherical pressure into atmospheres (atm). Altough it is possible to solve with kPa units, this reduced form remains the simpliest and the easiest to use. Here is an example:

What is the volume (in L) of 1 mole of an ideal gas at standard temperature (273 K) and at a pressure of 1 atm?

pV = nRT

V = nRT / P

V = (1mol x 0.08206 L atm mol^(-1) K^(-1) x 273K) / 1 atm

Canceling the atms, we have:

V = (1mol x 0.08206 L mol^(-1) K^(-1) x 273K) / 1

Canceling the mols and the K [(mol^(-1) K^(-1)) x (1mol x 273K)]:

V = (1 x 0.08206 L x 273) / 1

V = (1 x 0.08206 L x 273)

V = (0.08206 L x 273)

V = 22.4 L

Last edited by Sodapop; Oct 8th 2009 at 12:57 PM.
Sodapop is offline   Reply With Quote