I've been investigating chemical kinetics and stumbled across the CHEMKIN program manuals and the JANAF tables. In the original CHEMKIN database they list 'standard enthalpy'. I've checked and this is not in fact enthalpy of formation as this is a separately listed value. What I'm confused about is that I cannot find any reference to molar enthalpy any where else except in the the introduction to the JANAF tables and the CHEMKIN database. What's more it lists the enthalpy of $\ce{H2O}$ and $\ce{H2O2}$ as zero and other substances have negative enthalpy. Questions:
Is specific molar enthalpy in comparison to water or some other substance?
If it is still a relative measurement of enthalpy what advantage does it provide over heat of formation in practical use?
How can the two substances both have the same enthalpy even if it is relative if one has an extra atom and an extra bond?
Am I completely wrong and the whole thing is something else entirely?
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