∆H formed equals which species?

∆H formed equals which species?

• A. The products
• B. The reactants
• C. The catalysts
• D. The solvents

Answer: (A)

Standard enthalpy of formation is defined as the heat change when one mole of a compound is formed from its elements in their standard states. Because it describes the formation of the compound, the enthalpy change is associated with the product—the compound being formed. Catalysts and solvents don’t define this quantity, and the reactants are the starting materials, not the species for which the formation enthalpy is specified. So the enthalpy of formation corresponds to forming the product.

Standard enthalpy of formation is defined as the heat change when one mole of a compound is formed from its elements in their standard states. Because it describes the formation of the compound, the enthalpy change is associated with the product—the compound being formed. Catalysts and solvents don’t define this quantity, and the reactants are the starting materials, not the species for which the formation enthalpy is specified. So the enthalpy of formation corresponds to forming the product.