Is enthalpy of formation for water gas or liquid in this equation?

[engineering]

if i have the equation for enthalpy of water


overall enthalpy = enthalpy of formation + enthalpy of water 1800k - enthalpy of water at 298k


what is the value of enthalpy of formation is it enthalpy of formation of water as gas or liquid?

enthaply at 1800k would that be enthalpy of water as steam or vapour

enthalpy at 298k would that be steam or vapour?

 

[engware]

Hi there:

If you are doing steam calculations, just go with the steam tables.

If you are doing combustion calculations, then it is another story.

In general, it would be enthalpy of formation for water. Now you have to be careful. This is tricky. For low pressure combustion calculations, you deal with steam properties that are contained in steam tables when the pressure is 1 [atm]. This should do it for you.

Good questions, but one needs to be very carerful ...

Thanks,

Gordan