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Std enthalpy change of formation, Δ f H o liquid? kJ/mol Standard molar entropy, S o liquid: 117.8 J/(mol K) Heat capacity, c p: 67.4 J/(mol K) Gas properties Std enthalpy change of formation, Δ f H o gas +52.47 kJ/mol Standard molar entropy, S o gas: 219.32 J/(mol K) Enthalpy of combustion, Δ c H o –1387.4 kJ/mol Heat capacity, c p: 42.9 ...
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula C 2 H 4 or H 2 C=CH 2.It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. [7] It is the simplest alkene (a hydrocarbon with carbon–carbon double bonds).
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).
The enthalpy change for any standard reaction is designated ΔH° rx. Standard molar heat of formation of ZnBr 2 (c,l) from the elements, showing discontinuities at transition temperatures of the elements and the compound.
The Van 't Hoff equation relates the change in the equilibrium constant, K eq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, Δ r H ⊖, for the process. The subscript r {\displaystyle r} means "reaction" and the superscript ⊖ {\displaystyle \ominus } means "standard".
Such measurements often use a standard temperature of 25 °C (77 °F; 298 K) [citation needed]. This is the same as the thermodynamic heat of combustion since the enthalpy change for the reaction assumes a common temperature of the compounds before and after combustion, in which case the water produced by combustion is condensed to a liquid.
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).