adding two reactions together

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Valeria Viera 1B
Posts: 60
Joined: Fri Apr 06, 2018 11:05 am

adding two reactions together

Postby Valeria Viera 1B » Fri Jan 25, 2019 9:08 pm

Can anyone show me how to add to reactions together for Hess’s law? Or give an example?

Thank you!

Chris Freking 2G
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

Re: adding two reactions together

Postby Chris Freking 2G » Fri Jan 25, 2019 10:00 pm

From the lecture on 1/25/19:

N2(g) + O2(g) --> 2NO(g) (ΔHrxn = 180kJ)
2NO(g) + O2(g) --> 2NO2(g) (ΔHrxn = -112 kJ)

Adding the above reactions gives the net reaction:
N2(g) + 2O2(g) --> 2NO2(g) (Hnet = 68kJ)

Nicole Elhosni 2I
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: adding two reactions together

Postby Nicole Elhosni 2I » Sat Jan 26, 2019 1:31 pm

If you have trouble visualizing it, it is kind of like the transitive property in math. So if A-> B, and B->C, then A->C and you can add each reaction's change in enthalpy, A->B and B->C, to get the entire reactions change in enthalpy, so from A->C!


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