Which of the following can be calculated using the standard enthalpies of formation of reactants and products?

• A. The standard enthalpy change of a chemical reaction
• B. The rate constant of a reaction
• C. The activation energy of a reaction
• D. The equilibrium constant of a reaction

Answer: (A)

Verified step by step guidance

1. Understand that the standard enthalpy of formation (\( \Delta H_f^\circ \)) is the enthalpy change when one mole of a compound is formed from its elements in their standard states.
2. Recall that the standard enthalpy change of a chemical reaction (\( \Delta H_{rxn}^\circ \)) can be calculated using the standard enthalpies of formation of the reactants and products by applying Hess's Law.
3. Use the formula: \[ \Delta H_{rxn}^\circ = \sum \Delta H_f^\circ (\text{products}) - \sum \Delta H_f^\circ (\text{reactants}) \] where you sum the standard enthalpies of formation of all products and subtract the sum for all reactants, each multiplied by their stoichiometric coefficients.
4. Recognize that the rate constant and activation energy relate to the kinetics of the reaction and cannot be determined from enthalpies of formation alone.
5. Understand that the equilibrium constant depends on the Gibbs free energy change, which involves both enthalpy and entropy, so it cannot be directly calculated from standard enthalpies of formation without additional information.