The enthalpy of formation of tetraoxygen, also known as oxygen gas (O2), is the change in enthalpy that occurs when one mole of oxygen gas is formed from its constituent elements, oxygen atoms, in their standard states at a pressure of 1 bar (100 kPa) and a specified temperature (usually 25°C or 298 K).
The enthalpy of formation is an important thermodynamic property that measures the stability of a substance. It is used to determine the energy that is released or absorbed during a chemical reaction, as well as to calculate the heat of combustion and other thermodynamic quantities.
The enthalpy of formation of tetraoxygen is typically measured using calorimetric techniques, where the heat released or absorbed during the formation of oxygen gas is measured. This can also be calculated using Hess's law, which states that the enthalpy change of a reaction is independent of the pathway taken.
The standard enthalpy of formation of tetraoxygen is defined as the enthalpy of formation at standard conditions, which is 25°C (298 K) and 1 bar (100 kPa). For oxygen gas, the standard enthalpy of formation is 0 kJ/mol, as it is the most stable form of oxygen at these conditions.
The enthalpy of formation of tetraoxygen is relatively high compared to other elements, as it is a highly stable molecule. This is due to the strong diatomic bond between the oxygen atoms. However, the enthalpy of formation of oxygen gas is lower than other diatomic molecules, such as nitrogen gas (N2) and hydrogen gas (H2), due to the small size and high electronegativity of the oxygen atom.