In an exothermic reaction:
A) The reaction rate is always very high
B) Heat is absorbed from the surroundings
C) The products have the same chemical potential energy as the reactants
D) The products have lower chemical potential energy than the reactants
E) The reactants have lower chemical potential energy than the products
IMAT 2026 · Question 47
Q47 - Thermochemistry and reaction energy
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The correct answer is D) The products have lower chemical potential energy than the reactants.
An exothermic reaction releases energy to the surroundings as heat, so ΔH = H(products) − H(reactants) < 0. The energy released is exactly what the products have lost compared with the reactants. Example: burning methane.
A) Incorrect: How much energy a reaction releases says nothing about its speed. Iron rusting is exothermic but very slow.
B) Incorrect: Absorbing heat describes an endothermic reaction.
C) Incorrect: Equal energy would mean ΔH = 0: no heat released.
D) Correct: The products have less chemical potential energy, and the difference is released as heat.
E) Incorrect: That describes an endothermic reaction.
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