Standard reaction enthalpies

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Evelyn L 1H
Posts: 67
Joined: Fri Sep 29, 2017 7:05 am

Standard reaction enthalpies

Postby Evelyn L 1H » Sat Jan 20, 2018 4:57 pm

I am confused about how to calculate the standard reaction enthalpies. For example, in 8.63, part a asks to calculate the standard reaction enthalpy for the final stage in the production of nitric acid. 3NO2(g)+H2O(l) --> 2HNO3(aq) + NO(g).
What are the steps to finding the answer?

Connor Kelligrew 2D
Posts: 39
Joined: Fri Sep 29, 2017 7:07 am

Re: Standard reaction enthalpies

Postby Connor Kelligrew 2D » Sat Jan 20, 2018 5:30 pm

For this question, you can use the standard enthalpies of formation from Appendix 2A to calculate the standard reaction enthalpy, which is one of the methods to calculating a standard reaction enthalpy.
Imagine that to carry out the reaction we convert the reactants into the elements in their most stable form, then from those elements we form the products. I would suggest looking at Figure 8.31 on page 295 of the textbook to visualize it. This line of thinking gives us this equation:



So in this problem you would look up the standard enthalpies of formation for , , , and from Appendix 2A and use the equation above.
Hope this helps!


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