Related Resources: thermodynamics

### Individual and Universal Gas Constants

Individual and Universal Gas Constants

Universal gas constant is a physical constant that is featured in the ideal gas law and other fundamental equations in the physical sciences.

The specific heat capacities at constant pressure and constant volume processes, and the ratio of specific heat and the individual gas constant - R - for some common used "ideal gases", can be found in the table below (approximate values at 68°F (20°C) and 14.7 psia (1 atm)):

 Gas or Vapor Formula Specific Heat Capacity Ratio of Specific Heats Individual Gas Constant R cp (kJ/kg K) cv (kJ/kg K) cp (Btu/lbM°F) cv = (Btu/lbM°F) K = cp / cv cp-cv (kJ/Kg K) cp-cv (ft lnf/lbm°R) Acetone 1.47 1.32 0.35 0.32 1.11 0.15 Acetylene C2H2 1.69 1.37 0.35 0.27 1.232 0.319 59.34 Air 1.01 0.718 0.24 0.17 1.4 0.287 53.34 Alcohol C2H5OH 1.88 1.67 0.45 0.4 1.13 0.22 Alcohol CH3OH 1.93 1.53 0.46 0.37 1.26 0.39 Ammonia NH3 2.19 1.66 0.52 0.4 1.31 0.53 96.5 Argon Ar 0.52 0.312 0.12 0.07 1.667 0.208 Benzene C6H6 1.09 0.99 0.26 0.24 1.12 0.1 Blast furnace gas 1.03 0.73 0.25 0.17 1.41 0.3 55.05 Bromine 0.25 0.2 0.06 0.05 1.28 0.05 Butatiene 1.12 Butane C4H10 1.67 1.53 0.395 0.356 1.094 0.143 26.5 Carbon dioxide CO2 0.844 0.655 0.21 0.16 1.289 0.189 38.86 Carbon monoxide CO 1.02 0.72 0.24 0.17 1.4 0.297 55.14 Carbon disulphide 0.67 0.55 0.16 0.13 1.21 0.12 Chlorine Cl2 0.48 0.36 0.12 0.09 1.34 0.12 Chloroform 0.63 0.55 0.15 0.13 1.15 0.08 Combustion products 1 0.24 Ethane C2H6 1.75 1.48 0.39 0.32 1.187 0.276 51.5 Ether 2.01 1.95 0.48 0.47 1.03 0.06 Ethylene C2H4 1.53 1.23 0.4 0.33 1.24 0.296 55.08 Freon 22 1.18 Helium He 5.19 3.12 1.25 0.75 1.667 2.08 386.3 Hexane 1.06 Hydrogen H2 14.32 10.16 3.42 2.43 1.405 4.12 765.9 Hydrogen Chloride HCl 0.8 0.57 0.191 0.135 1.41 0.23 42.4 Hydrogen Sulfide H2S 0.243 0.187 1.32 45.2 Hydroxyl OH 1.76 1.27 1.384 0.489 Methane CH4 2.22 1.7 0.59 0.45 1.304 0.518 96.4 Methyl Chloride CH3Cl 0.24 0.2 1.2 30.6 Natural Gas 2.34 1.85 0.56 0.44 1.27 0.5 79.1 Neon 1.03 0.618 1.667 0.412 Nitric Oxide NO 0.995 0.718 0.23 0.17 1.386 0.277 Nitrogen N2 1.04 0.743 0.25 0.18 1.4 0.297 54.99 Nitrogen tetroxide 4.69 4.6 1.12 1.1 1.02 0.09 Nitrous oxide N2O 0.88 0.69 0.21 0.17 1.27 0.18 35.1 Oxygen O2 0.919 0.659 0.22 0.16 1.395 0.26 48.24 Pentane 1.07 Propane C3H8 1.67 1.48 0.39 0.34 1.127 0.189 35 Propene (propylene) C3H6 1.5 1.31 0.36 0.31 1.15 0.18 36.8 Water Vapor 1.93 1.46 0.46 0.35 1.32 0.462 Steam 1 psia. 120 – 600 °F Steam 14.7 psia. 220 – 600 °F 1.97 1.5 0.47 0.36 1.31 0.46 Steam 150 psia. 360 – 600 °F 2.26 1.76 0.54 0.42 1.28 0.5 Sulfur dioxide (Sulphur dioxide) SO2 0.64 0.51 0.15 0.12 1.29 0.13 24.1

K = cp / cv, the specifi heat capacity ratio
cp = specifc heat in a constant pressure process
cv = specific heat in a constant volume porcess
R = Individual Gas Constant

In SI units the value of the gas constant, R, is:
R =8.314510 Pa m3 K-1 mol-1
R = 8314.510 Pa L K-1 mol-1
R = 0.08314510 bar L K-1 mol-1

Source: Various, NASA, Penn State University, Wikipedia, Standard University

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