Method One (Hess’s Law)

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Drew Myers 4G
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

Method One (Hess’s Law)

Postby Drew Myers 4G » Sun Jan 26, 2020 1:16 pm

Can someone give a quick explanation of how to use Hess’s Law?

Aarja Pavade 1H
Posts: 103
Joined: Sat Aug 17, 2019 12:18 am

Re: Method One (Hess’s Law)

Postby Aarja Pavade 1H » Sun Jan 26, 2020 1:30 pm

Hess's Law states that enthalpy changes are additive. Thus, the enthalpy change at each step of a multi-step reaction can be added to give the total enthalpy change. ex: delta Hrxn1 + delta Hrxn2= delta Hnet (adding reactions to obtain net reaction).

505316964
Posts: 95
Joined: Thu Jul 11, 2019 12:17 am

Re: Method One (Hess’s Law)

Postby 505316964 » Sun Jan 26, 2020 1:38 pm

If you have two equations that can be added together to get the wanted composite equation, you can add the deltaHRXN of each equation to get the net deltahHRXN.

smurphy1D
Posts: 51
Joined: Mon Nov 18, 2019 12:18 am

Re: Method One (Hess’s Law)

Postby smurphy1D » Sun Jan 26, 2020 2:19 pm

Are the equations we add together ones we have to put together ourselves or will they usually be given?

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Method One (Hess’s Law)

Postby Alice Chang 2H » Sun Jan 26, 2020 4:18 pm

https://www.khanacademy.org/science/chemistry/thermodynamics-chemistry/enthalpy-chemistry-sal/v/hess-s-law-example

Khan Academy pulling through with a worked example! If you're more of a visual learner, this might help.


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