Although the data is not stated, the standard enthalpy of formation of ammonia is -46 kJ/mol.
The standard enthalpy of formation of a substance is the change in enthalpy that occurs when one mole of that substance is produced from its elements in their standard states. The fact that the standard enthalpy of formation for ammonia is negative indicates that the formation of ammonia is an exothermic, or energy releasing, reaction.
