Enthalpy of formation | Thermodynamics | AP Chemistry | Khan Academy
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- เผยแพร่เมื่อ 19 ก.ย. 2024
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The standard enthalpy of formation of a compound is the enthalpy change that occurs when 1 mole of the compound is formed from its constituent elements in their standard states. A pure element in its standard state has a standard enthalpy of formation of zero. For any chemical reaction, the standard enthalpy change is the sum of the standard enthalpies of formation of the products minus the sum of the standard enthalpies of formation of the reactants. View more lessons or practice this subject at www.khanacadem...
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This is useful I’ll keep it
How come Enthalpy of Formation is calculated differently from the typical chemical reaction under non-standard conditions (DeltaH)? For the latter, all one needs to do in order to find a reaction's change in enthalpy is re-arrange the additional (intermediate) chemical reactions (if needed) (altering their Delta H too) and then simply add their enthalpies.
The way Enthalpy of Formation is calculated also seems to, in a way, not follow Hess's law and the fact that energy is a state function. Maybe, because I learned how to solve for enthalpy change of reactions under non-standard conditions first I haven't considered the entire meaning of Enthalpy. But, how come it is not correct to just add all the enthalpy of formations (with their potential alterations) to determine the main reaction's change in enthalpy of formation?
Good