Page 1 of 1

### Hess' Law

Posted: Fri Jan 31, 2020 10:32 am
Why can we add or subtract enthalpy changes?

### Re: Hess' Law

Posted: Fri Jan 31, 2020 10:35 am
Enthalpy is a state property, meaning that it is not dependent on the path taken to obtain that state, and state properties can be added or subtracted.

### Re: Hess' Law

Posted: Fri Jan 31, 2020 11:01 am
Since it is a state property, only the final and initial state will matter. This allows us to add and subtract the values of enthalpy.

### Re: Hess' Law

Posted: Fri Jan 31, 2020 11:51 am
Yes! Because enthalpy is a state property, we can add or subtract the enthalpy changes in order to get to an overall reaction since the path we take to get there doesn't matter.

### Re: Hess' Law

Posted: Fri Jan 31, 2020 3:53 pm
yes! this is because it is a state property

### Re: Hess' Law

Posted: Fri Jan 31, 2020 4:26 pm
Enthalpy changes can be added and subtracted because enthalpy is a state property.

### Re: Hess' Law

Posted: Fri Jan 31, 2020 6:03 pm
State properties are allowed to be added or subtracted to each other.

### Re: Hess' Law

Posted: Fri Jan 31, 2020 6:29 pm
Enthalpy is a state property, so only the final and initial states matter. The process by which you get from an initial state to a final state does not matter for state properties. Therefore, if you want to find the enthalpy value of a reaction through Hess' Law, you can just add the enthalpy values (ensuring that the intermediates cancel out).