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Since the pressure of the standard formation reaction is fixed at 1 bar, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a single temperature: 298 K, represented by the symbol Δ f H ⦵ 298 K.
Standard enthalpy of formation is the enthalpy change when one mole of any compound is formed from its constituent elements in their standard states. The enthalpy of formation of one mole of ethane gas refers to the reaction 2 C (graphite) + 3 H 2 (g) → C 2 H 6 (g).
Regardless of the equation format, the heat of formation of a compound at any temperature is ΔH° form at 298.15 K, plus the sum of the heat content parameters of the products minus the sum of the heat content parameters of the reactants. The C p equation is obtained by taking the derivative of the heat content equation.
Heat capacity, c p? J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid –271.2 kJ/mol Standard molar entropy, S o liquid: 253.5 J/(mol K) Enthalpy of combustion, Δ c H o –2726.3 kJ/mol Heat capacity, c p: 172.0 J/(mol K) Gas properties Std enthalpy change of formation, Δ f H o gas –252.7 kJ/mol Standard molar ...
Heat capacity, c p: 74.5 J/(mol K) at –22 °C 82.8 J/(mol K) at 0 °C Liquid properties Std enthalpy change of formation, Δ f H o liquid –425.5 kJ/mol Standard molar entropy, S o liquid: 129.0 J/(mol K) Enthalpy of combustion, Δ c H o –254.6 kJ/mol Heat capacity, c p: 101.3 J/(mol K) at 20–100 °C Gas properties Std enthalpy change of ...
This equation quickly enables the calculation of the Gibbs free energy change for a chemical reaction at any temperature T 2 with knowledge of just the standard Gibbs free energy change of formation and the standard enthalpy change of formation for the individual components. Also, using the reaction isotherm equation, [8] that is
Enthalpy change of sublimation at 273.15 K, Δ sub H: 51.1 kJ/mol Std entropy change of sublimation at 273.15 K, 1 bar, Δ sub S ~144 J/(mol·K) Molal freezing point constant: −1.858 °C kg/mol Molal boiling point constant: 0.512 °C kg/mol Solid properties Std enthalpy change of formation, Δ f H o solid: −291.83 kJ/mol Standard molar ...
Heat capacity, c p [2] 96 J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid: −249.4 kJ/mol Standard molar entropy, S o liquid: 200.4 J/(mol K) Enthalpy of combustion, Δ c H o –1785.7 kJ/mol Heat capacity, c p: 125.5 J/(mol K) Gas properties Std enthalpy change of formation, Δ f H o gas: −218.5 kJ/mol Standard ...