8.57

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Jessica Lutz 2E
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

8.57

Postby Jessica Lutz 2E » Thu Jan 11, 2018 6:12 pm

This is number 57:
Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2(g) + 2 H2(g) -> C2H6(g), from the following data: Hc (C2H2, g)=-1300. kJ·mol^-1, Hc (C2H6, g)= -1560. kJ·mol^-1, Hc (H2, g)= -286 kJ·mol^-1.
Is the c subscript important to answering this problem? What makes it different than just H?

Alvin Tran 2E
Posts: 39
Joined: Fri Sep 29, 2017 7:06 am

Re: 8.57

Postby Alvin Tran 2E » Thu Jan 11, 2018 6:32 pm

The c makes it stand for enthalpy of combustion. You have to write a reaction for the combustion of each of the compounds (by adding O2) so that you can find out their enthalpy of formation. From there, you can use Hess's Law to calculate enthalpy for the hydrogenation of ethyne to ethane reaction.


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