Question

What is the enthalpy of formation of 1/2 O2 gas

Answer 1

Answer:

zero

To understand standard enthalpy of formation of O2 Equal to Zero, you need to understand the definition of standard enthalpy of formation. This is the change of enthalpy when one mole of a substance in its standard state is formed from its elements under standard state conditions of 1 atmosphere pressure and 298K temperature. Oxygen gas consists of its elements already in the standard state, so there isn't any change here. Oxygen (the element) at standard state is O2.