Question

pick out the incorrect statement(s) about endothermic reaction. bond energy of reactants is lower than the bond energy of products. enthalpy change is always positive. energy profile diagram shows a downhill trend. both a and b

Explanation:

• For an endothermic reaction, the bond energy of reactants is lower than that of products (as energy is absorbed to break bonds and form higher - energy products), and the enthalpy change ($\Delta H$) is positive (since $H_{products}>H_{reactants}$ and $\Delta H=H_{products}-H_{reactants}$).
• In an energy - profile diagram of an endothermic reaction, the energy of products is higher than that of reactants, so it shows an uphill trend, not a downhill trend.

Answer:

Energy profile diagram shows a downhill trend.