In equations (1) and (2), the standard reaction enthalpies are given.
(1) What is the enthalpy of formation of nitrogen dioxide?
The enthalpy of formation is the heat released per mole when a compound is formed from its elements. Equation (1) gives the enthalpy of formation of two moles of nitrogen dioxide. Therefore, the given enthalpy, when divided by 2, gives the enthalpy of formation of nitrogen dioxide. The enthalpy of formation of is 33.18 kJ/mol.