Question

The bond dissociation energies of gaseous H₂, Cl₂, and HCl are 104, 58, and 103 kcal, respectively. The enthalpy of formation of HCl gas would be:

• A. -44 kcal
• B. -88 kcal
• C. -22 kcal
• D. -11 kcal

Hint:

The enthalpy of formation of a compound from its elements can be calculated using bond dissociation energies. Remember to apply the stoichiometric coefficients to the BDEs of the reactants and products, and subtract the energy of bonds formed from the energy of bonds broken. For standard enthalpy of formation, ensure the equation forms one mole of the compound from elements in their standard states.