Enthalpy of formation of a *compound* is the change in enthalpy during the formation of the compound from its constituent *elements in reference state* It is denoted by $\Delta_{f}H^{\ominus}$ JANAF thermo-chemical tables provide enthalpy of formation for a lot of compounds https://janaf.nist.gov/ ## 1. Standard Enthalpy of formation Standard enthalpy of formation is the enthalpy of formation at "standard pressure and temperature" which is typically 1bar (100kPa) and 25°C It is denoted by ${\Delta_{f}}_{STP}H^{\ominus}$ ## 2. Sensible Enthalpy of formation Its the difference between absolute enthalpy of formation (in current temperature and pressure) and standard enthalpy of formation. It is typically the specific heat times delta T from standard conditions. Sensible enthalpy is solely a function of temperature rise from standard conditions $h_f(T)={\Delta_{f}}_{STP}H^{\ominus} + \left(h_f(T)-h_{fSTP}^{\ominus}\right)$ enthalpy of formation = standard enthalpy + sensible enthalpy ## 3. How to tell an oxidizer from a fuel - Fuels have high enthalpy of formation