Hess's Law

Moderators: Chem_Mod, Chem_Admin

Renee Delamater 2H
Posts: 31
Joined: Wed Nov 16, 2016 3:02 am

Hess's Law

Postby Renee Delamater 2H » Wed Jan 17, 2018 9:21 pm

What exactly does Hess's Law state?

Matthew Lin 2C
Posts: 30
Joined: Fri Sep 29, 2017 6:06 am

Re: Hess's Law

Postby Matthew Lin 2C » Wed Jan 17, 2018 9:24 pm

Hess's Law states (according to the book) that "the overall reaction enthalpy is the sum of the reaction enthalpies of the
steps into which the reaction can be divided." For example, if you the enthalpies of two reactions that make up one overall reaction, you can find the enthalpy of the overall reaction by adding the enthalpies of the two reactions. Let me know if you need further clarification about it!

Renee Delamater 2H
Posts: 31
Joined: Wed Nov 16, 2016 3:02 am

Re: Hess's Law

Postby Renee Delamater 2H » Wed Jan 17, 2018 9:34 pm

Thanks! So how does this equation and idea relate to specific heat? Is specific heat involved in the equation to find enthalpy because it is needed in each step of a specific reaction?

Dang Lam
Posts: 55
Joined: Thu Jul 27, 2017 2:01 am

Re: Hess's Law

Postby Dang Lam » Thu Jan 18, 2018 11:12 am

i don't think it has to do with specific heat.

Sally Nason - 1K
Posts: 40
Joined: Fri Sep 29, 2017 6:05 am

Re: Hess's Law

Postby Sally Nason - 1K » Thu Jan 18, 2018 11:31 am

Since enthalpy is a state function, it doesn't matter what path is taken to the final point, the only values that matter are final and initial. That is why you can "skip" intermediate steps by adding equations.

Michael Lee 2I
Posts: 51
Joined: Fri Sep 29, 2017 6:05 am

Re: Hess's Law

Postby Michael Lee 2I » Thu Jan 18, 2018 10:12 pm

The only thing you really need to know, since the path taken does not matter, is final state - initial state.


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 2 guests