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Question on Enthalpy. Please help!

I would appreciate any help with the following question:

Calculate the dHf of butane (C4H10) using the following data:

dHc for graphite = -393.5kJ/mol
dHc for hydrogen = -285.9kJ/mol
dHc for butane = -2877.1kJ/mol

Thanks!!

Study Forum Helper

construct the equation required by adding and subtracting these other equations

C + O2 --> CO2 -393.5kJ/mol
H2 + 1/2O2 --> H2O -285.9kJ/mol
C4H10 + 13/2O2 --> 4CO2 + 5H2O -2877.1kJ/mol

making sure that you do the same with the energy values

OP

thanks! though whats the required equation ? 4C + 5H2 ---> C4H10 ???

4C + 10H ---> C4H10 Remember, enthalpy change of formation is the enthalpy change when a compound is formed from its constituent elements.

Study Forum Helper

... in their states under standard conditions .... 4C(graphite) + 5H2(g) --> C4H10

OP

coldfusion

4C + 10H ---> C4H10 Remember, enthalpy change of formation is the enthalpy change when a compound is formed from its constituent elements.

ok hence 4C + 5H2 ---> C4H10 must also be acceptable??

Thanks to both of you.

Study Forum Helper

not only acceptable but correct

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