Hess's Law

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hazelyang2E
Posts: 57
Joined: Fri Sep 28, 2018 12:23 am

Hess's Law

Postby hazelyang2E » Sat Feb 09, 2019 11:09 pm

Can someone please explain how to differentiate when we should use Hess's Law to calculate the overall reactions enthalpy versus using the sum of the enthalpies of formation of the products minus the sum of the enthalpies of the reactants? Will they yield the same result if you use them on the same reaction, or are their certain conditions that signal the use of one method over the other?

Chem_Mod
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Re: Hess's Law

Postby Chem_Mod » Sun Feb 10, 2019 2:33 am

They will yiled the same answer! You can use either method but usually only certain information is given which requires you to use one method.

Lumbini Chandrasekera 1B
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

Re: Hess's Law

Postby Lumbini Chandrasekera 1B » Sun Feb 10, 2019 12:45 pm

Essentially the two mean the same thing. Using the summation method is just finding the reaction enthalpy value yourself.

Julia Lung 1I
Posts: 30
Joined: Fri Jun 23, 2017 11:39 am

Re: Hess's Law

Postby Julia Lung 1I » Sun Feb 10, 2019 2:16 pm

Usually the problem gives you values or tells you what method to use to solve for the enthalpy


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