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For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
It may provide or confirm basic enthalpy data needed for the calculation of phase diagrams of metals, via CALPHAD or ab initio quantum chemistry methods. For a binary system composed by elements A and B, a generic Miedema Formula could be cast as Δ H = f ( E l e m e n t A , P h i A , n W S A , V A , E l e m e n t B .
Standard enthalpy of combustion is the enthalpy change when one mole of an organic compound reacts with molecular oxygen (O 2) to form carbon dioxide and liquid water. For example, the standard enthalpy of combustion of ethane gas refers to the reaction C 2 H 6 (g) + (7/2) O 2 (g) → 2 CO 2 (g) + 3 H 2 O (l).
Enthalpy of fusion or melting. This applies to the transition of a solid to a liquid and is designated ΔH m. Enthalpy of vaporization. This applies to the transition of a liquid to a vapor and is designated ΔH v. Enthalpy of sublimation. This applies to the transition of a solid to a vapor and is designated ΔH s.
Liquid properties Std enthalpy change of formation, Δ f H o liquid: −318.2 kJ/mol Standard molar entropy, S o liquid: 180 J/(mol K) Heat capacity, c p: 2.68 J/(gK) at 20°C-25°C Gas properties Std enthalpy change of formation, Δ f H o gas: −261.1 kJ/mol Standard molar entropy, S o gas: 333 J/(mol K) Heat capacity, c p: 1.54 J/(gK) at 25°C
Liquid properties Std enthalpy change of formation, Δ f H o liquid: −238.4 kJ/mol Standard molar entropy, S o liquid: 127.2 J/(mol K) Enthalpy of combustion Δ c H o: −715.0 kJ/mol Heat capacity, c p: 70.8–90.5 J/(mol K) (at −97.6 to 64.7 °C) [5] 79.9 J/(mol K) at 20 °C Gas properties Std enthalpy change of formation, Δ f H o gas ...
The Joback method, often named Joback–Reid method, predicts eleven important and commonly used pure component thermodynamic properties from molecular structure only. It is named after Kevin G. Joback in 1984 [1] and developed it further with Robert C. Reid. [2] The Joback method is an extension of the Lydersen method [3] and uses very similar groups, formulas, and parameters for the three ...
Liquid properties Std enthalpy change of formation, Δ f H o liquid: −393.5kJ/mol Standard molar entropy, S o liquid: 213.7J/(mol K) Heat capacity, [10] c p: