Which chemical equation represents the standard enthalpy of formation of a substance?

💡 Solution & Explanation

The standard enthalpy of formation is defined as the enthalpy change accompanying the synthesis of precisely one mole of a substance from its constituent elements in their most stable thermodynamic standard states at standard conditions. Alternative equations describing substance decomposition, combustion in oxygen, or physical dissolution do not fulfill the precise criteria of formation thermochemistry. The standard enthalpy of formation for any element in its reference state is defined as zero.