Information AboutHeat Of Vaporization |
| CATEGORIES ABOUT ENTHALPY OF VAPORIZATION | |
| chemical properties | |
| thermodynamics | |
| heat | |
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The enthalpy of vaporization, (symbol ), also known as the '''heat of vaporization''' or '''heat of evaporation''', is the in the measured value. Values are usually quoted in KJ / Mol , although kJ/ Kg , Kcal /mol, cal/g and Btu / Lb are also possible, among others. The enthalpy of condensation (or '''heat of condensation''') is numerically exactly equal to the enthalpy of vaporization, but has the opposite sign: enthalpy changes of vaporization are always positive ( Heat is absorbed by the substance), whereas enthalpy changes of condensation are always negative (heat is released by the substance). The enthalpy of vaporization can be viewed as the energy required to overcome the must be used to obtain a true value of the Bond Energy . An alternative description is to view the enthalpy of condensation as the heat which must be released to the surroundings to compensate for the drop in Entropy when a gas condenses to a liquid. As the liquid and gas are in Equilibrium at the boiling point (''T''b), Δv''G'' = 0, which leads to: : As neither entropy nor of a liquid is small. These two definitions are equivalent: the boiling point is the temperature at which the increased entropy of the gas phase overcomes the intermolecular forces. As a given quantity of matter always has a higher entropy in the gas phase than in a condensed phase ( is always positive), and from :, the Gibbs Free Energy change falls with increasing temperature: gases are favored at higher temperatures, as is observed in practice. SELECTED VALUES Elements Enthalpies of vaporization of the elements in kJ/mol Other common substances Common substances sorted by heat of vaporization: SEE ALSO REFERENCES Sears, Zemansky et al., University Physics, Addison-Wessley Publishing Company, Sixth ed., 1982, ISBN 0-201-07199-1 |
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