8.57? I don't understand the way the solutions manual solved the problem?

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Adriana Rangel 1A
Posts: 96
Joined: Fri Sep 29, 2017 7:04 am

8.57? I don't understand the way the solutions manual solved the problem?

Postby Adriana Rangel 1A » Tue Mar 13, 2018 6:22 pm

8.57 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·mol1
DELTA Hc(C2H6, g) = -1560. kJ·mol1
DELTA Hc(H2, g)= - 286 kJ·mol1

So I used the formula: DELTA H rxn= Sum of H products- Sum of H reactants and got:
= -1560 -( (2 x -286) + -1300)= 312....
The solutions manual got negative 312? And also they did it differently? I don't understand what they did?

Tiffany Dao 1A
Posts: 32
Joined: Fri Sep 29, 2017 7:05 am

Re: 8.57? I don't understand the way the solutions manual solved the problem?

Postby Tiffany Dao 1A » Tue Mar 13, 2018 8:22 pm

Since it's combustion, you would add the enthalpis of combustion together. Also, you would have to change the sign for C2H6 because it's a product.


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