## Change in Enthalpy from Reactants to Products

Enrico Cortes
Posts: 7
Joined: Fri Sep 25, 2015 3:00 am

### Change in Enthalpy from Reactants to Products

What are the different ways to determine the change in Enthalpy from Reactants to Products in a standard state?

Jonathan Shih 3H
Posts: 37
Joined: Fri Sep 25, 2015 3:00 am

### Re: Change in Enthalpy from Reactants to Products

There are three ways:
1. Using Hess's law and using the standard change in enthalpies for different but similar reaction and using substitution and such like shown in the course reader example, we can find the change of enthalpy for the specific reaction we're looking for.
2. We can look at individually the bonds broken and formed and use bond enthalpies to find the standard enthalpy for the reaction. Following, the example given in the course reader, what we generally do is sum of the bond enthalpies of the bonds broken minus the sum of the bond enthalpies of the bonds broken.
3. Using the standard enthalpy of the formation reactions, we can calculate the standard enthalpy of the reaction by calculating the standard enthalpy of products minus the standard enthalpy of the reactants.

Hope this helps!