Enthalpy of Reaction v. Enthalpy of Formation

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Layal Suboh 1I
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

Enthalpy of Reaction v. Enthalpy of Formation

Postby Layal Suboh 1I » Wed Jan 30, 2019 10:43 pm

Hello,

What is the difference between the enthalpy of reaction and the enthalpy of formation? Are they calculated the same way?


Thanks

Searra Harding 4I
Posts: 68
Joined: Fri Sep 28, 2018 12:29 am

Re: Enthalpy of Reaction v. Enthalpy of Formation

Postby Searra Harding 4I » Wed Jan 30, 2019 11:06 pm

I saw this question was asked on chem community before and here was their answer: "The reaction enthalpy is the heat given off or taken up for the rxn, i.e., the enthalpy difference between the reactants and products. The enthalpy of formation of a compound is the enthalpy change between the elements in their standard state (reactants) and the compound (product). One could 1st calculate the enthalpy of formation for all the reactants and all products and then calculate their difference. Using product - reactant in both cases. However if you are given bond enthalpies then it makes more sense to use them. Since a bond enthalpy is a measure of the energy needed to break that bond (+ve) then it is more direct to count up the number of bonds broken (+ve) and the number of bonds formed (energy releasing, -ve) and add."


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