In a reaction where the products are higher in energy than the reactants, ∆H is...

In a reaction where the products are higher in energy than the reactants, ∆H is...

• A. Negative
• B. Positive
• C. Zero
• D. Undefined

Answer: (B)

Heat flow at constant pressure is tied to the difference in energy between the products and the reactants. If the products end up at a higher energy than the reactants, the system must take in energy from the surroundings to form those products. That makes the enthalpy change positive: ΔH = H_products − H_reactants > 0. This is an endothermic process, where heat is absorbed. If the products were lower in energy, ΔH would be negative (heat released); if they were the same energy, ΔH would be zero. Undefined would not apply here since there is a definite energy difference.

Heat flow at constant pressure is tied to the difference in energy between the products and the reactants. If the products end up at a higher energy than the reactants, the system must take in energy from the surroundings to form those products. That makes the enthalpy change positive: ΔH = H_products − H_reactants > 0. This is an endothermic process, where heat is absorbed. If the products were lower in energy, ΔH would be negative (heat released); if they were the same energy, ΔH would be zero. Undefined would not apply here since there is a definite energy difference.