Standard enthalpy change of formation: the definition and the sign
Dr Lavan Ganeshkumar, PhD · updated 4 October 2026
The standard enthalpy change of formation is the enthalpy change when one mole of a compound is formed from its elements in their standard states, under standard conditions.
Words that must appear
- One mole of a compound
- From its elements
- In their standard states
The sign
The value for an element in its standard state is zero. Compounds can be positive or negative.
Do not confuse with
Enthalpy of combustion, which burns a substance in oxygen.
Common questions
What is the standard enthalpy change of formation?
The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions.
What is the standard enthalpy of formation of an element?
Zero.
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