Formula for CO2

P1XV1 = P2XV2

V2 = P1XV1/P2 = 2000X80/40 = 4000 CU FT

........which is true for an ideal gas.

CO₂ tends to solidify at the sorts of temperatures that can be experienced during adiabatic_expansion, and can be found as a liquid at some pressures and temperatures, so the starting and finishing temperatures for the expansion must be fixed before an accurate answer can be found to the above question. http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=26#GeneralData gives more information.

This is a trick question. At room temperature, CO2 will liquify at less than 1000 psi.

You don't give a temperature so I'll assume liquid and gas are at 60°F. Critical temp is 88°F and critical pressure 1072 psi so at 2000 psi and 60°F it is liquid. Liquid density is ~ 48 lb/ft³ so mass = 48 x 80 = 3840 lb. Mol. wt. of CO₂ = 44 so gas density at 60°F (15°C) and 40 psia = 44/22.4 x 273/288 x (40 + 14.7)/14.7 = 6.9 kg/m³ = 0.434 lb/ft³. So volume = 3840/0.434 = 8848 ft³.

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