Hess's Law

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ng1D
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Hess's Law

Postby ng1D » Sat Jan 25, 2020 9:24 am

What is Hess's Law and how does it relate to state properties?

Amanda Mei 1B
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Joined: Sat Aug 24, 2019 12:16 am

Re: Hess's Law

Postby Amanda Mei 1B » Sat Jan 25, 2020 11:11 am

Hess's Law states that enthalpy is a state function, so its value is determined by its current state, not the path taken to obtain that state. Thus, the total enthalpy change of a multi-step reaction can be calculated by adding the enthalpy change at each step of the reaction.

Rebekah Alfred 1J
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Re: Hess's Law

Postby Rebekah Alfred 1J » Sat Jan 25, 2020 11:32 am

In the textbook, it says Hess's law states that "the overall reaction enthalpy is the sum of the reaction enthalpies of the steps into which the reaction can be divided."

Radha Patel 4I
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Re: Hess's Law

Postby Radha Patel 4I » Sat Jan 25, 2020 11:37 am

Hess's Law states that the total change in enthalpy in a reaction is the sum of all energy changes in the reaction. It does not depend on the pathway needed to reach the end point of the reaction, as Professor Lavelle had explained with the mountain example, the enthalpy change does not depend on the pathway between the initial and final states of the reaction.

Kassidy Ford 1I
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Re: Hess's Law

Postby Kassidy Ford 1I » Sat Jan 25, 2020 12:58 pm

if something is a state property, that means be addition and subtraction can be used on it. So Hess's law relates to this because you can add enthalpies of reactions together to find the overall enthalpy of reaction

Izzie Capra 2E
Posts: 103
Joined: Sat Sep 07, 2019 12:19 am

Re: Hess's Law

Postby Izzie Capra 2E » Sat Jan 25, 2020 1:28 pm

Yes, and sometimes you will have to manipulate the steps of the reaction to form the proper additive, final reaction. For example, you can make a forward reaction a reverse reaction by multiplying the enthalpy value by a negative. Or, you can multiply a step of the reaction by an integer in order to get the products and reactants to cancel our properly.


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