Final answer:
Bond enthalpies can be used to calculate the enthalpy of a reaction under constant pressure conditions for both gaseous and non-gaseous reactions, and for both exothermic and endothermic reactions.
Step-by-step explanation:
We can use bond enthalpies to calculate the enthalpy of a reaction under constant pressure conditions, which is option d). This is applicable to both gaseous and non-gaseous reactions and irrespective of whether the reactions are exothermic or endothermic. Calculating enthalpy changes using bond energies is especially useful when enthalpies of formation are not available. The enthalpy change (ΔH) can be estimated by subtracting the sum of the bond energies of the bonds formed from the sum of the bond energies of the bonds broken.
An exothermic reaction will have a negative ΔH, indicating that the energy released from forming new bonds is greater than the energy needed to break the original bonds. Conversely, an endothermic reaction has a positive ΔH, meaning the energy required to break bonds in the reactants is greater than the energy released when new bonds are formed in the products.