Which of the following best describes an endothermic reaction?

• A. Heat is released to the surroundings
• B. A negative enthalpy change (ΔH < 0)
• C. A positive enthalpy change (ΔH > 0)
• D. The products have lower energy than the reactants

Answer: (C)

Verified step by step guidance

1. Understand that an endothermic reaction is one in which the system absorbs heat from the surroundings.
2. Recall that enthalpy change (\( \Delta H \)) represents the heat absorbed or released during a reaction at constant pressure.
3. Recognize that if heat is absorbed, the enthalpy change is positive (\( \Delta H > 0 \)), meaning the products have higher energy than the reactants.
4. Contrast this with exothermic reactions, where heat is released, enthalpy change is negative (\( \Delta H < 0 \)), and products have lower energy than reactants.
5. Therefore, the best description of an endothermic reaction is that it has a positive enthalpy change (\( \Delta H > 0 \)).