Standard Enthalpy of Formation

[Adam Kramer 1A]

When do we use the standard enthalpy of formation? I feel like I always see it but I never use it, so when would we?

[romina_4C]

Usually a question asking to calculate the change in enthalpy of a reaction will give you a table of the enthalpies of formation, which would require you to use that method to find the change in enthalpy. Sometimes it is easier to use the enthalpies of formation to calculate enthalpy change because elements in their standards states have enthalpies of formation of zero (H2, O2, C (graphite), etc.).

[Max Madrzyk Dis 4G]

You would use the standard enthalpy of formation values when the question is asking for the standard enthalpy. If the question is not asking for standard enthalpy there will usually be other values given so that you can calculate the standard enthalpy in a different method.

[Matthew Chan 1B]

If you're asked for the enthalpy change of some reaction or whatever, you'll typically be provided with values that correspond to the standard enthalpies of formation for certain components of the reaction that you can then use in your calculations to determine enthalpy change of a reaction, etc.