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Carbon Dioxide - Thermophysical Properties

Chemical, physical and thermal properties of carbon dioxide. Phase diagram included.

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Carbon dioxide, CO2, is a colourless and odorless gas. It is relatively nontoxic and noncombustible, but it is heavier than air and may asphyxiate by the displacement of air. 

When CO2 is solved in water, the mild carbonic acid, is formed. Cooled CO2 in solid form is called dry ice.

Chemical, physical and thermal properties of carbon dioxide:
Values are given for gas phase at 25oC /77oF / 298 K and 1 atm., if not other phase, temperature or pressure given.

Property Value Unit Value Unit Value Unit Value Unit
Acidity (pKa1) 6.35
Acidity (pKa2) 10.33
Boiling Point - sublimation point 194.686 K -78.464 °C -109.24 °F
Critical density 10.63 mol/dm3 467.6 kg/m3 0.9073 slug/ft3 29.19 lb/ft3
Critical pressure 7.38 MPa=MN/m2 73.8 bar 72.8 atm 1070 psi=lbf/in2
Critical temperature 304.13 K 30.98 °C 87.76 °F
Critical volume 94.12 cm3/mol 0.00214 m3/kg 1.102 ft3/slug 0.03426 ft3/lb
Density 40.8 mol/m3 1.795 kg/m3 0.00348 slug/ft3 0.1121 lb/ft3
Density, gas at 32°F/0°C 1 atm 44.9 mol/m3 1.977 kg/m3 0.00384 slug/ft3 0.1234 lb/ft3
Density, liquid at -34.6 °F/-37°C, saturation pressure 25017 mol/m3 1101 kg/m3 2.136 slug/ft3 68.73 lb/ft3
Density, solid at -109.3 °F/-78.5°C, 1 atm 35492 mol/m3 1562 kg/m3 3.031 slug/ft3 97.51 lb/ft3
Flammable no
Gas constant - R (individual) 188.92 J/kg K 0.0525 Wh/(kg K) 1130 [ft lbf/slug °R] 35.114 [ft lbf/lb °R]
Gibbs free energy of formation -394.00 kJ/mol -8953 kJ/kg -3849 Btu/lb
Heat (enthalpy) of combustion 0 kJ/mol 0 kJ/kg 0 Btu/lb
Heat (enthalpy) of formation -393.50 kJ/mol -8941 kJ/kg -3844 Btu/lb
Heat (enthalpy) of fusion 9.02 kJ/mol 205 kJ/kg 88.11 Btu/lb
Heat (enthalpy) of sublimation, at 180 K 26 kJ/mol 591 kJ/kg 254 Btu/lb
Heat (enthalpy) of evaporation at 15°C 16.70 kJ/mol 379.5 kJ/kg 163.14 Btu/lb
Heat (enthalpy) of evaporation at triple point 15.55 kJ/mol 353.4 kJ/kg 151.93 Btu/lb
Heat capacity, Cp (isobaric) 37.35 J/mol K 0.849 kJ/kg K 0.203 Btu/lb°F or cal/g K
Heat capacity, Cv (isochoric) 28.96 J/mol K 0.658 kJ/kg K 0.157 Btu/lb°F or cal/g K
Ionization potential 13.77 eV
Molecular Weight 44.0095 g/mol 0.09702 lb/mol
pH of saturated aqueous solution 3.7
Solubility in water 0.148 g/100 g 1.48 g/l=mg/ml
Sound velocity in gas 269 m/s
Specific Gravity (density relativ to density of air) 1.53
Specific Heat Ratio - Cp/Cv 1.29
Specific Volume 0.0245 m3/mol 0.557 m3/kg 287.1 ft3/slug 8.92 ft3/lb
Standard molar entropy, S° 213.8 J/mol K 4.86 kJ/kg K 1.16 Btu/lb °F
Sublimation Point 194.686 K -78.464 °C -109.24 °F
Surface tension at melting point 16.2 dynes/cm
Thermal Conductivity 0.01663 W/m°C 0.009609 Btu/hr ft °F
Triple point pressure 0.5180 MPa=MN/m2 5.180 bar 5.112 atm 75.12 psi=lbf/in2
Triple point temperature 216.59 K -56.56 °C -69.81 °F
Vapor (saturation) pressure 6.45 MPa=MN/m2 48379 mm Hg 63.66 atm 935.5 psi=lbf/in2
Viscosity, dynamic (absolute) 1.495 cP 1004.6 [lbm/ft s*10-6] 31.22 [lbf s/ft2 *10-6]
Viscosity, kinematic 0.834 cSt 8.977 [ft2/s*10-6]

Follow the links below to get values for the listed properties of carbon dioxide at varying pressure and temperature:

Carbon dioxide is a gas at standard conditions. However, at low temperature and/or high pressures the gas becomes a liquid or a solid.

The phase diagram for carbon dioxide shows the phase behavior with changes in temperature and pressure. The curve between the critical point and the triple point shows the carbon dioxide boiling point with changes in pressure. The curve between thr triple point downwards to zero pressure shows the sublimation point with changes in pressure (Sublimation: transformation from solid phase directly to gas phase). Carbon dioxide in solid phase is called dry ice.

CO2 phase diagram C

At the critical point there is no change of state when pressure is increased or if heat is added.

The triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.

See also more about atmospheric pressure, and STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure, as well as Thermophysical properties of:
Acetone,  AcetyleneAir, Ammonia, Argon, Butane, Carbon dioxide, Carbon monoxide, Ethane, Ethanol, Helium, Hydrogen, Methane, Methanol, Nitrogen, Oxygen, Propane, Water and Heavy water, D2O.

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