Ethylene Oxide - Physical Properties

Physical Properties

Ethylene oxide is a colorless gas at 25 °C and is a mobile liquid at 0 °C – viscosity of liquid ethylene oxide at 0 °C is about 5.5 times lower than that of water. The gas has a characteristic sweet odor of ether, noticeable when its concentration in air exceeds 500 ppm. Ethylene oxide is readily soluble in water, ethanol, diethyl ether and many organic solvents.

Main thermodynamical constants are:

  • Standard molar heat capacity, Cp° = 48.19 J/(mol·K);
  • Standard enthalpy of formation, ΔH°298 = −51.037 kJ/mol;
  • Standard entropy, S°298 = 243.4 J/(mol·K);
  • Gibbs free energy, ΔG°298 = −11.68 kJ/mol;
  • Heat of combustion, ΔHc° = −1306 kJ/mol.

The surface tension of liquid ethylene oxide, at the interface with its own steam, is 35.8 mJ/m2 at −50.1 °C and 27.6 mJ/m2 at −0.1 °C.

The boiling point increases with the vapor pressure as follows: 57.7 (2 atm), 83.6 (5 atm) and 114.0 (10 atm).

Viscosity decreases with temperature with the values of 0.577 kPa·s at −49.8 °C, 0.488 kPa·s at −38.2 °C, 0.394 kPa·s at −21.0 °C and 0.320 kPa·s at 0 °C.

Between −91 °C and 10.5 °C, vapor pressure p (in mmHg) varies with temperature (T in °C) as lg p = 6.251 – 1115.1/(244.14 + T).

Properties of liquid ethylene oxide
Temperature, °C Steam pressure, kPa Enthalpy of the liquid,
J/g		 Enthalpy of vaporization,
J/g		 Density, kg/L Heat capacity, J/(kg·K) Thermal conductivity, W/(m·K)
−40 °C 8.35 0 628.6 0.9488 1878 0.20
−20 °C 25.73 38.8 605.4 0.9232 1912 0.18
0 °C 65.82 77.3 581.7 0.8969 1954 0.16
20 °C 145.8 115.3 557.3 0.8697 2008 0.15
40 °C 288.4 153.2 532.1 0.8413 2092 0.14
60 °C 521.2 191.8 505.7 0.8108 2247 0.14
80 °C 875.4 232.6 477.4 0.7794 2426 0.14
100 °C 1385.4 277.8 445.5 0.7443 2782 0.13
120 °C 2088 330.4 407.5 0.7052 3293 N/A*
140 °C 3020 393.5 359.4 0.6609 4225 N/A
160 °C 4224 469.2 297.1 0.608 N/A N/A
180 °C 5741 551.2 222.5 0.533 N/A N/A
195.8 °C 7191 N/A N/A N/A N/A N/A

*N/A – data not available.

Properties of ethylene oxide vapor
Temperature, K Entropy, J/(mol·K) Heat of formation, kJ/mol Free energy of formation, kJ/mol Viscosity Pa·s Thermal conductivity, W/(m·K) Heat capacity, J/(mol·K)
298 242.4 −52.63 −13.10 N/A N/A 48.28
300 242.8 −52.72 −12.84 9.0 0.012 48.53
400 258.7 −56.53 1.05 13.5 0.025 61.71
500 274.0 −59.62 15.82 15.4 0.038 75.44
600 288.8 −62.13 31.13 18.2 0.056 86.27
700 302.8 −64.10 46.86 20.9 0.075 95.31
800 316.0 −65.61 62.80 N/A 0.090 102.9

*N/A – data not available.

Read more about this topic:  Ethylene Oxide

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