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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.
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). 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 ...
All elements in their reference states (oxygen gas, solid carbon in the form of graphite, etc.) have a standard enthalpy of formation of zero, as there is no change involved in their formation. The formation reaction is a constant pressure and constant temperature process. Since the pressure of the standard formation reaction is fixed at 1 bar ...
The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
Enthalpy is the transfer of energy in a reaction (for chemical reactions, it is in the form of heat) and is the change in enthalpy. Δ H {\displaystyle \Delta H} is a state function, meaning that Δ H {\displaystyle \Delta H} is independent of processes occurring between initial and final states.
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
Std enthalpy change of formation, Δ f H o liquid? kJ/mol Standard molar entropy, S o liquid: 126.7 J/(mol K) Heat capacity, c p: 68.5 J/(mol K) at −179 °C Gas properties Std enthalpy change of formation, Δ f H o gas: −83.8 kJ/mol Standard molar entropy, S o gas: 229.6 J/(mol K) Enthalpy of combustion, Δ c H o: −1560.7 kJ/mol Heat ...
Ethane (US: / ˈ ɛ θ eɪ n / ETH-ayn, UK: / ˈ iː-/ EE-) is a naturally occurring organic chemical compound with chemical formula C 2 H 6. At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petrochemical by-product of petroleum ...