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# Application of Hess's Law watch

1. hi there i am stuck on this question and wondered if anyone could help me ??

calculate the enthalpy change for the complete combustion of butane. use the enthalpies of combustion of hydrogen and carbon from your data book and the enthalpy of the formation of butane.
4C(s) + 5H2 (g) = c4H10 (g)

2. (Original post by BRobertson99)
hi there i am stuck on this question and wondered if anyone could help me ??

calculate the enthalpy change for the complete combustion of butane. use the enthalpies of combustion of hydrogen and carbon from your data book and the enthalpy of the formation of butane.
4C(s) + 5H2 (g) = c4H10 (g)

Have you come across the diagrams you can draw for Hess's law questions?
3. (Original post by BRobertson99)
calculate the enthalpy change for the complete combustion of butane. use the enthalpies of combustion of hydrogen and carbon from your data book and the enthalpy of the formation of butane.
4C(s) + 5H2 (g) = c4H10 (g)

Because we're using ΔcH data, the thermochemical cycle arrows will be heading down from our reactants and products!
So we'll be using ΔH(direct) = ΔH(indirect1) - ΔH(indirect2)

1) ΔcH values (you can get these from your data book and just swap them in for my values).
--> ΔcHC: -393.5 kJ/mol
--> ΔcHH2: -285.8 kJ/mol
-->ΔcHC4H10: -2877.5 kJ/mol

2) Put in numbers!
ΔH(direct) = [(4)(-393.5) + (5)(-285.8)] - (-2855.5)

3) Calculator

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