Hess's Law

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Jared Smith 1E
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Hess's Law

Postby Jared Smith 1E » Sat Jan 20, 2018 10:34 pm

I have a couple of questions relating to calculation's using Hess's Law. First, why is it ok to use fractions in the chemical equations? I read the explanation in the textbook, but it didn't really help. Second, when should I use fractions as stoichiometric coefficients in Hess's Law calculations?


Scott Chin_1E
Posts: 55
Joined: Sat Jul 22, 2017 3:00 am

Re: Hess's Law

Postby Scott Chin_1E » Sat Jan 20, 2018 11:51 pm

I think that it is acceptable to use fractions in the coefficients for Hess's Law because the final reaction is the sum of all the intermediate reactions, therefore, fractions of each reactant can exist in the intermediate reactions.

Fractions may be useful in Hess's Law calculations because it may make cancelling both sides of the reactions (reactant and product) much easier and simpler.

Jason Liu 1C
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am

Re: Hess's Law

Postby Jason Liu 1C » Sun Jan 21, 2018 12:15 am

Since the intermediate steps in Hess's Law are only used to find the enthalpy of the overall reaction, the intermediate steps do not necessarily have to be able to be carried out. Therefore, it is OK to use fractions because all you need are values to calculate the overall reaction's enthalpy.

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