Why is the enthalpy of combustion zero for oxygen?

[Daniel2244]

Homework Statement

Why is enthalpy of combustion 0KJmol-1 for oxygen?
I need to know this for my exam coming up soon.

Homework Equations

The enthalpy change when 1 mole of a substance is burnt in excess oxygen under standard states under standard conditions.

The Attempt at a Solution

Oxygen requires 0 energy to form as it is a natural element.

 

[Borek]

By definition I would say. II doesn't burn, it stays unchanged.

 

[Daniel2244]

By definition I would say. II doesn't burn, it stays unchanged.

That makes sense. Thanks for the help.