CO2 Air Guns

Recently, my friend showed me his air gun that was powered by a CO2 cartridge. I thought it was pretty cool, so I wanted to look at the chemistry behind how CO2 guns work. By the way, in no way do I encourage the use of guns in any ways whatsoever. Don't shoot people with guns.




                                        CO2 powered gun

CO2 guns are powered by a CO2 cartridge, which is basically a metallic container that has CO2 mixed with a little oil and pressurized into liquid form. The ones I have seen are 12 grams CO2. When you put the CO2 cartridge into the gun and pull the trigger, a valve connects the bottle to the gun, releasing a blast of compressed gas and propelling the bullet.

The most interesting thing I found about this contraption is that the CO2 cartridge becomes very cold after being fired. I made a flow chart to delineate this process.

This process is also related to the ideal gas law. PV=nRT, as P decreases by firing the gun, V will increase, T will also decrease. Its important to note that for this process, the CO2 does not produce cold air, rather it takes away heat.