to calculate enthalpies
ab initio is a difficult task, and requires intense use of quantummechanical approaches.
Hence, almost all enthalpy data you'll find for whatsoever substances are measured, either directly or indirectly.
To measure the enthalpy of formation for acetone directly, i.e. to observe the process
6 C + 6 H
2 + O
2 2 CH
3COCH
3 to he best of my knowledge is impossible, as this won't happen (i.e. is a purely theoretical process)
However, you might calculate the enthalpy of formation for acetone indirectly - if you knew the enthalpy of combustion for acetone , for example, and made use of
Hess's lawregards
Ingo