Standard heats (enthalpies) of formation of compounds, $\Delta$H°_f, may be positive or negative.

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Standard heats of formation are defined as the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions. The standard heats of formation of compounds can be positive or negative, depending on the relative strengths of the bonds in the reactants and products. Positive values indicate that more energy is required to form the compound than is released, while negative values indicate that less energy is required to form the compound than is released.

Standard Heats (Enthalpies) of Formation of Compounds Δ\DeltaΔ H°f, May Be Positive or Negative

Standard Heats (Enthalpies) of Formation of Compounds $\Delta$ H°_f, May Be Positive or Negative