Question 8.57 (Sixth Edition)

Moderators: Chem_Mod, Chem_Admin

Steve Magana 2I
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

Question 8.57 (Sixth Edition)

Postby Steve Magana 2I » Mon Feb 04, 2019 12:14 am

Question: Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2(g) + 2 H2(g) --> C2H6(g), from the following data: deltaHc(C2H2, g) = -1300. kJ/mol, deltaHc(C2H6, g) = -1560. kJ/mol, deltaHc(H2, g) = -286 kJ/mol.

I was able to do this problem, but my answer does not match the solutions manual. Can someone help me with this to see where I went wrong please? Thank you!

Madeline Ho 1C
Posts: 37
Joined: Mon Apr 23, 2018 3:00 am

Re: Question 8.57 (Sixth Edition)

Postby Madeline Ho 1C » Mon Feb 04, 2019 12:23 am

I'm having trouble with this too... I did the sum of the standard enthalpy of combustion for products - reactants but I got +312 kJ instead of -312 kJ. I know it should be negative because it's a combustion reaction, thus exothermic, but that math doesn't match up.

Alexa_Henrie_1I
Posts: 61
Joined: Fri Sep 29, 2017 7:03 am

Re: Question 8.57 (Sixth Edition)

Postby Alexa_Henrie_1I » Tue Feb 05, 2019 2:44 pm

I am also confused about this problem. My answer doesn't match the solutions manual either.

Madeline Ho 1C
Posts: 37
Joined: Mon Apr 23, 2018 3:00 am

Re: Question 8.57 (Sixth Edition)

Postby Madeline Ho 1C » Tue Feb 05, 2019 4:25 pm

viewtopic.php?t=17644
I found this thread that explains how to do the problem well. Essentially, you have to find the combustion reaction for each element of the given reaction and then use method 1 for solving for enthalpy to find the reaction enthalpy for the hydrogenation of ethyne to ethane.


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 2 guests