Homework Problem 8.51

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Stevie Wisz
Posts: 59
Joined: Fri Sep 25, 2015 3:00 am

Homework Problem 8.51

Postby Stevie Wisz » Mon Jan 11, 2016 8:46 pm

In this question it has the reaction 4 C7H5N3O6 + 21 O2 yields 28 CO2 + 10 H2O + 6 N2
When calculating the enthalpy for the entire reaction you do the sum of the enthalpies of the products minus that of the reactants. Although in the solutions manual, when calculating that, the enthalpy of the N2 was not included. Can some explain to me why the N2 was left out of the reaction enthalpy calculation? thank you :)

Cindy Chen_2I
Posts: 43
Joined: Wed Nov 18, 2015 3:00 am

Re: Homework Problem 8.51

Postby Cindy Chen_2I » Mon Jan 11, 2016 11:32 pm

Because the standard enthalpy of formation of an element in its most stable form (in this case N2) is zero. (See course reader p.19)
That's why you can leave it out.

Stevie Wisz
Posts: 59
Joined: Fri Sep 25, 2015 3:00 am

Re: Homework Problem 8.51

Postby Stevie Wisz » Wed Jan 13, 2016 5:54 pm

thank you!


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