Final answer:
The statement that the reactants contain more energy is correct for the endothermic reaction provided, where the reactants absorb heat from the surroundings and have higher chemical potential energy.
Step-by-step explanation:
For the reaction Ba(OH)2 + 8H2O + 2NH4NO3 + heat → 10H2O + 2NH3 + Ba(NO3)2, the correct statement is that the reactants contain more energy. When heat is mentioned on the reactant side, it indicates that heat is being absorbed, meaning the reaction is endothermic. An endothermic reaction absorbs energy from its surroundings, so the reactants must have a higher chemical potential energy than the products. The absorbed energy is transformed into chemical energy in the products, which have stronger bonds than the reactants, as suggested by the enthalpy change (AH) for an endothermic process.