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).
| 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.
| 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.
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