[anappleaday]

my teacher went over the standard molar enthalpy of formation, but on the homework there are some problems i need to calculate the molar enthalpy of combustion. Can anyone explain to me what's the difference between these two and do they use the same formula? thnx

[sdekivit]

molar enthalpy of formation is the enthalpychange of the formation of 1 mol compound out of its elements.

molar enthalpy of cumbustion is the enthalpy change of the combustion of 1 mol compound.

for example:

C + 2H2 --> CH4 --> enthalpychange of the formationreaction.

CH4 + 2O2 --> CO2 + 2H2O --> enthalpy of the combustionreaction of CH4.