Heat of Formation
Watch this video, which defines the heat of formation (△Hf) as the energy change involved in forming one mole of a compound from its elements in their natural form. The presenter tabulates the heat of formations for most common compounds, which can be used to calculate the enthalpy change of a reaction if you have a balanced chemical equation. You can use the sign of the enthalpy of reaction to determine if the reaction is endothermic (positive enthalpy) or exothermic (negative enthalpy).
Source: Khan Academy, https://youtu.be/eOwjD6Za1rk
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