Standard Enthalpy of Formation

[Julie Mai 1K]

Hello!

I was wondering why the standard enthalpy of formation for O2 = 0? During lecture, Lavelle solved for the standard enthalpy of combustion of methane as an example for method 3: standard enthalpies of formation and the standard of enthalpy of formation for O2 was 0.

[AlexandriaHunt2J]

The standard enthalpy of formation of O2 is zero because the oxygen element naturally exists as O2 in the standard state conditions of 1atm and 298 K. Because O naturally exists as O2, that means no energy is required to form it, so standard enthalpy of formation = 0 kJ/mol.

[Ashley Presnell 1C]

Lavelle mentioned that the standard enthalpy of formation of elements in their natural state like O2 for oxygen or N2 for nitrogen would be 0. Since it is the naturally more stable form of the element, it doesn't require energy to form it, but rather would require energy to form a different structure of it that is not as stable as it would favor the formation of O2.

[Maham Kazmi 2J]

Hi! I remember that Dr. Lavelle explained it in a way where the standard enthalpy of formation is a reference point. It's like how we call sea level 0 altitude regardless of whether or not it truly is. It allows us to compare other values. So in general, any molecule in its natural state would have a standard enthalpy of formation of 0.

[Yuhan Sun]

The definition of standard enthalpy of formation is the enthalpy change of one mole from a substance in its elements in their most stable form.
O2, N2, H2 etc. these are just the most stable form from its elements. So the amount of change is 0.

[405479701]

In the lecture, we learned the standard enthalpy of formation of any element in its natural state is 0. For example, N2 for nitrogen or 02 for oxygen would be 0.

[Lesley Kim 1K]

The standard enthalpy of formation is zero as O2 requires no energy in order for the molecule to exist as O2 is already oxygen's natural state or its most stable form.

[Achyutha Kodavatikanti_3H]

standard enthalpy of formation of diatomic elements like O2 is 0 because that's how they exist in nature. there is no energy needed to form O2.

[Nicole Ton 3C]

The standard enthalpy of formation is the standard reaction enthalpy for the formation of a mole of the substance from their element in the most stable form. Standard enthalpy of formation is under standard condition and using elements in their standard state. Oxygen's most stable form is O2, so O2's standard enthalpy of formation is 0.