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Std enthalpy change of vaporization, Δ vap H o: 44.0 kJ/mol Enthalpy change of vaporization at 373.15 K, Δ vap H: 40.68 kJ/mol Std entropy change of vaporization, Δ vap S o: 118.89 J/(mol·K) Entropy change of vaporization at 373.15 K, Δ vap S: 109.02 J/(mol·K) Enthalpy change of sublimation at 273.15 K, Δ sub H: 51.1 kJ/mol Std entropy ...
The specific enthalpy of fusion (more commonly known as latent heat) of water is 333.55 kJ/kg at 0 °C: the same amount of energy is required to melt ice as to warm ice from −160 °C up to its melting point or to heat the same amount of water by about 80 °C. Of common substances, only that of ammonia is higher.
Temperature-dependency of the heats of vaporization for water, methanol, benzene, and acetone. In thermodynamics, the enthalpy of vaporization (symbol ∆H vap), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy that must be added to a liquid substance to transform a quantity of that substance into a gas.
J.A. Dean (ed.), Lange's Handbook of Chemistry (15th Edition), McGraw-Hill, 1999; Section 6, Thermodynamic Properties; Table 6.4, Heats of Fusion, Vaporization, and Sublimation and Specific Heat at Various Temperatures of the Elements and Inorganic Compounds
The kelvin was defined so that the triple point of water is exactly 273.16 K, but that changed with the 2019 revision of the SI, where the kelvin was redefined so that the Boltzmann constant is exactly 1.380 649 × 10 −23 J⋅K −1, and the triple point of water became an experimentally measured constant.
The critical point of water occurs at 647.096 K (373.946 °C; 705.103 °F) and 22.064 megapascals (3,200.1 psi; 217.75 atm; 220.64 bar). [3] In the vicinity of the critical point, the physical properties of the liquid and the vapor change dramatically, with both phases becoming even more similar.
The percentage of water vapor in surface air varies from 0.01% at -42 °C (-44 °F) [15] to 4.24% when the dew point is 30 °C (86 °F). [16] Over 99% of atmospheric water is in the form of vapour, rather than liquid water or ice, [17] and approximately 99.13% of the water vapour is contained in the troposphere.
For a liquid–gas transition, is the molar latent heat (or molar enthalpy) of vaporization; for a solid–gas transition, is the molar latent heat of sublimation. If the latent heat is known, then knowledge of one point on the coexistence curve , for instance (1 bar, 373 K) for water, determines the rest of the curve.