enthalpy of the given reaction is 4721 KJ since 4 moles of boron are used enthalpy change / mole boron = 4721/4 = 1180 KJ/mol Solution enthalpy of the given reaction is 4721 KJ since 4 moles of boron are used enthalpy change / mole boron = 4721/4 = 1180 KJ/mol.