Ammonia - Thermophysical Properties
Ammonia is a colourless gas with a characteristic pungent smell and hazardous in its concentrated form.
Chemical, physical and thermal properties of Ammonia, NH3 :
Values at 25 oC (77 oF, 298 K) and 1 atm, if not other temperature and pressure given.
If values are given for liquid ammonia at ambient temperature, the ammonia is pressurized above 1 atm.
For full table with Imperial units - rotate the screen!
| Property | Value | Unit | Value | Unit | Value | Unit | Value | Unit | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Acidity (pKa) | 9.24 | ||||||||||
| Acidity (pKa) at -33°C | 32.5 | ||||||||||
| Autoignition point | 903 | K | 630 | °C | 1166 | °F | |||||
| Basicity (pKb) | 4.75 | ||||||||||
| Boiling point | 239.82 | K | -33.33 | °C | -27.99 | °F | |||||
| Critical density | 14327 | mol/m3 | 243.99 | kg/m3 | 15.23 | lb/ft3 | 0.4734 | slug/ft3 | |||
| Critical pressure | 11.357 | MPa=MN/m2 | 113.57 | bar | 112.08 | atm | 1647.2 | psi=lbf/in2 | |||
| Critical temperature | 405.56 | K | 132.41 | °C | 270.34 | °F | |||||
| Critical volume | 69.8 | cm3/mol | 0.00410 | m3/kg | 0.0657 | ft3/lb | 2.11 | ft3/slug | |||
| Density, gas | 41.1 | mol/m3 | 0.699 | kg/m3 | 0.0437 | lb/ft3 | 0.00136 | slug/ft3 | |||
| Density, liquid at -28 °F/-33.35°C, 1 atm | 40868 | mol/m3 | 696 | kg/m3 | 43.4 | lb/ft3 | 1.35 | slug/ft3 | |||
| Density, liquid at 70 °F/21.1°C | 36259 | mol/m3 | 617.5 | kg/m3 | 38.55 | lb/ft3 | 1.198 | slug/ft3 | |||
| Flammable | no | ||||||||||
| Flash point | 405 | K | 132 | °C | 269 | °F | |||||
| Gas constant, R | 488.2 | J/kg K | 0.1356 | Wh/(kg K) | 90.74 | ft lbf/lb °R | 2919 | ft lbf/slug °R | |||
| Gibbs free energy of formation, ΔGf | -16.6 | kJ/mol | -975 | kJ/kg | -0.42 | Btu/lb | |||||
| Heat (enthalpy) of combustion, ΔHc (gas) | 382.8 | kJ/mol | 22477 | kJ/kg | 9.663 | Btu/lb | |||||
| Heat (enthalpy) of evaporation, ΔHv, at boiling point | 23.37 | kJ/mol | 1372.0 | kJ/kg | 589.87 | Btu/lb | |||||
| Heat(enthalpy) of formation, ΔHf (gas) | -45.9 | kJ/mol | -2695 | kJ/kg | -1.16 | Btu/lb | |||||
| Heat (enthalpy) of fusion/melting, ΔHm | 5.653 | kJ/mol | 332.3 | kJ/kg | 143 | Btu/lb | |||||
| Heat (enthalpy) of sublimation, ΔHS , at 180 K | 31.2 | kJ/mol | 1832 | kJ/kg | 0.79 | Btu/lb | |||||
| Ionization potential | 10.18 | eV | |||||||||
| Melting (freezing) point | 195.42 | K | -77.73 | °C | -107.91 | °F | |||||
| Molecular Weight | 17.03052 | g/mol | 0.03755 | lb/mol | |||||||
| pH of 0.01 N aqueous solution | 10.6 | ||||||||||
| pH of 0.1 N aqueous solution | 11.1 | ||||||||||
| pH of 1.0 N aqueous solution | 11.6 | ||||||||||
| Standard molar entropy, S° (gas) at 1 bar | 192.77 | J/mol K | 11.32 | kJ/kg K | 0.002704 | Btu/lb °F | |||||
| Solubility in water, at 20°C | 540 | mg/ml | |||||||||
| Solubility in water, at 24°C | 482 | mg/ml | |||||||||
| Sound velocity in gas | 415 | m/s | |||||||||
| Specific Gravity, gas (density relativ to air) | 0.604 | ||||||||||
| Specific heat (heat capacity), Cp (gas) | 37.0 | J/mol K | 2.175 | kJ/kg K | 0.5200 | Btu/lb°F = cal/g K |
|||||
| Specific heat (heat capacity), Cp (liquid) | 80.8 | J/mol K | 4.744 | kJ/kg K | 1.133 | Btu/lb°F = cal/g K |
|||||
| Specific heat ratio - Cp/Cv (gas) | 1.32 | ||||||||||
| Specific volume | 0.02435 | m3/mol | 1.43 | m3/kg | 22.91 | ft3/lb | 736.99 | ft3/slug | |||
| Surface tension at 11.1°C/52.0°F | 23.4 | dynes/cm | |||||||||
| Surface tension at 34.1°C/93.4°F | 18.1 | dynes/cm | |||||||||
| Thermal Conductivity | 0.026 | W/m°C | 0.015 | Btu/hr ft °F | |||||||
| Triple point pressure | 0.00609 | MPa=MN/m2 | 0.0609 | bar | 0.0601 | atm | 0.883 | psi=lbf/in2 | |||
| Triple point temperature | 195.5 | K | -77.65 | °C | -107.77 | °F | |||||
| Vapor (saturation) pressure | 1.00 | MPa=MN/m2 | 7500 | mm Hg | 9.869 | atm | 145.0 | psi=lbf/in2 | |||
| Vapor (saturation) pressure at -49.72°F/-45.4°C | 0.0533 | MPa=MN/m2 | 400 | mm Hg | 0.526 | atm | 7.73 | psi=lbf/in2 | |||
| Viscosity, dynamic (absolute) (gas) | 0.0100 | cP | 6.72 ×10-6 | lbm/ft s | 0.209 ×10-6 | lbf s/ft2 | |||||
| Viscosity, dynamic (absolute) at 27°C (liq) | 0.1293 | cP | 86.89 ×10-6 | lbm/ft s | 2.70 ×10-6 | lbf s/ft2 | |||||
| Viscosity, dynamic (absolute) at -33.5°C (liq) | 0.255 | cP | 171.4 ×10-6 | lbm/ft s | 5.326 ×10-6 | lbf s/ft2 |
See also the following documents for changes in ammonia properties with changes in pressure and temperature:
- Density at varying temperature and pressure
- Dynamic and Kinematic Viscosity
- Liquid Ammonia - Thermal Properties at Saturation Pressure
- Prandtl number
- Properties at Gas-Liquid Equilibrium Conditions
- Specific heat
- Thermal Conductivity at Varying Temperature and Pressure
- Vapour Pressure at gas-liquid 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, Acetylene, Air, Argon, Benzene, Butane, Carbon dioxide, Carbon monoxide, Ethane, Ethanol, Ethylene, Helium, Hydrogen, Hydrogen sulfide, Methane, Methanol, Nitrogen, Oxygen, Pentane, Propane, Toluene, Water and Heavy water, D2O.
Ammonia is a gas at standard conditions. However, at low temperature and/or high pressures the gas becomes a liquid. The phase diagram for ammonia shows the phase behavior with changes in temperature and pressure. The curve between the triple point and the critical point shows the ammonia boiling point with changes in pressure.
Below the triple point temperature, ammonia becomes a solid, this phase will also be present at very high pressure (> 10 000 bar) and ambient temperature.
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.
Solubility of Ammonia in Water
Related Topics
• Boiling Points of Fluids
Boiling points of elements, products and chemical species at varying conditions.
• Densities
Densities of solids, liquids and gases. Definitions and convertion calculators.
• Fluid Mechanics
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
• Material Properties
Properties of gases, fluids and solids. Densities, specific heats, viscosities and more.
• Melting and Freezing Points
Melting and freezing points of elements and chemical species at varying conditions.
• Thermodynamics
Work, heat and energy systems.
• Viscosities
Viscosities of products and chemical species at varying conditions.
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