## Standard Enthalpies of Formation

$\Delta U=q+w$

Ardo 2K
Posts: 31
Joined: Fri Sep 29, 2017 7:05 am

### Standard Enthalpies of Formation

So when calculating the total enthalpy of a reaction and we are given standard enthalpies of formation of the individual products and reactants all we need to do from there is add up the bonds formed in the products and the bonds broken in the reactants and subtract the total enthalpy of the formed bonds by the broken bonds?

Andrea Grigsby 1I
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

### Re: Standard Enthalpies of Formation

the two are different but that's how you would do a calculation of the enthalpy of reaction through bond enthalpies
Last edited by Andrea Grigsby 1I on Sun Jan 21, 2018 11:51 pm, edited 1 time in total.

Emily Oren 3C
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

### Re: Standard Enthalpies of Formation

Using standard enthalpies of formation and using bond enthalpies are actually two different methods of calculating the enthalpy of the reaction. If you are given standard enthalpies of formation (SEF), do the sum of the SEF of the products minus the sum of the SEF of the reactants to get the enthalpy of the reaction. This is more accurate than using bond enthalpies (BE), but if you are given BE, you do the sum of the BE of the bonds broken minus the sum of the BE of the bonds formed.

Virpal Gill 1B
Posts: 32
Joined: Thu Jul 27, 2017 3:00 am

### Re: Standard Enthalpies of Formation

Multiply the standard enthalpies of formation times the number of moles for the products and add them all together. Do the same for the reactants. Then, subtract the total of the products by the total of the reactants.