[hairy_legged_geek]

I'm doing my A level Chemistry coursework and wish to state Hess's law within it.
However, there are many versions of the law around and I don't know which one is best to use.

I imagine that Hess did not write the law straight off but wrote some long paper about it, so can you please suggest the best (not necessarily the simplest)version of the law to use or the one closest to his original statement.

Thank you very much!

Alice

[Arkcon]

I don't think the text you chose to quote as Hess's Law is as important as your explanation of it.  A quick Wikipedia check doesn't lead me to suspect that there's a short and sweet version to use at all.  Do you have a favorite version or two that you'd like to share?

[DevaDevil]

the simplest way of explaining Hess' Law is

delta H⁰ = delta H_products - delta H_reactants = Sum_{(x = 1,n)} {delta H_{step (x)}}
(= delta H_{step 1} + delta H_{step 2} + ... + delta H_{step n} )
with n being the number of steps (partial reactions) in the reaction.

In words: the entalpy change of the reaction is determined by the enthalpy of the products minus the enthalpy of the reactants. This enthalpy change can be calculated by adding together the enthalpy changes of the various steps in the reaction.


I also have not heard of a very straightforward, mathematical equation to describe this.