Note: Pressure must be in atm, volume must be in L, and
temperature must be in K. The constant R is .0821 L atm/ mol K.
Modeled on the Kinetic Theory of Gases which has 4 basic postulates:
- Gases consist of molecules which are in continuous random motion
- The volume of the molecules present is negligible compared to the total volume occupied by the gas
- Intermolecular forces are neglibible
- Pressure is due to the gas molecules colliding with the walls of the container
Example: Calculate the volume (L) occupied by 7.40 g NH3 at STP.
First, list the knowns.
- V= ?
- T=273.15K
- P= 1.00 atm
- n= 7.40 g x (1 mol/17.04g) = .434 g
- R=.0821
Then, plug in the values into the equation to solve for V.
- PV=nRT
- 1.00V=.434 x .0821 x 273.15
- V = 9.73 L