Exothermic reactions release energy

Steps:

• Define exothermic reaction: heat is released to surroundings, so system loses energy (ΔH < 0).
• Analyze energy diagram: vertical axis shows potential energy; exothermic reactions have products at lower energy than reactants.
• Check statement C: thermodynamics (exothermic) does not guarantee kinetics; many require heating to overcome activation energy.
• Note D is incomplete, so cannot evaluate.

Why B is correct:

• By definition, exothermic reactions have lower product energy than reactants, so diagrams show products below reactants level (ΔH = E_products - E_reactants < 0).

Why the others are wrong:

• A: While typically true, some contexts (e.g., certain conventions) may vary, but standardly ΔH is negative—however, question focuses on universal diagram representation.
• C: Exothermic does not mean spontaneous or heat-free; activation energy often requires input.
• D: Not enough information.

Final answer: B