Visual representation of exothermic reactions

Steps:

• Define exothermic reaction: releases heat to surroundings, ΔH < 0.
• Recall reaction pathway diagram: plots potential energy vs. progress, ΔH as vertical difference.
• Check statement B: products at lower energy level than reactants.
• Assess C: spontaneity and rate depend on activation energy, not just ΔH.

Why B is correct:

• ΔH = H_products - H_reactants < 0 means products have lower enthalpy, so diagrams show them below reactants per standard convention.

Why the others are wrong:

• A: This is actually correct by definition, but may not apply universally if reaction direction reverses.
• C: Many exothermic reactions need initial heating to overcome activation energy barrier.
• D: Not enough information.

Final answer: B