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Enthalpy question A level Chemistry

'The standard enthalpy change of three combustion reactions is given below in kJ.
2 C2H6(g) + 7 O2(g) --> 4 CO2(g) + 6 H2O(g) delta H= -3120
2 H2(g) + O2(g) --> 2 H2O(g) delta H= -572
C2H4(g) + 3 O2(g) --> 2 CO2(g) + 2 H2O(g)

Based on the above information, calculate the standard enthalpy for the following reaction:

C2H6(g) --> C2H4(g) + H2(g) '

Please help!!

Thank you :smile:
You want to construct a Hess cycle with the desired equation at the top and the combustion products at the bottom :yep:
Original post by EierVonSatan
You want to construct a Hess cycle with the desired equation at the top and the combustion products at the bottom :yep:

I have that, but should I divide the first value by 2 because the delta H is for two moles of C2H2 , while I only want one?
Original post by Sad.Little.Donut
I have that, but should I divide the first value by 2 because the delta H is for two moles of C2H2 , while I only want one?

Yep, first and second enthalpy values need to be halved.
Original post by EierVonSatan
Yep, first and second enthalpy values need to be halved.

Okay thanks so much!

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