Energy Diagram Analysis for Reaction Kinetics

Steps:

• Identify ΔH_forward as energy difference between reactants and products; negative if exothermic (products lower).
• Determine Ea_forward as energy barrier from reactants to transition state; always positive.
• Determine Ea_backward as energy barrier from products to transition state; always positive.
• Compare signs: ΔH_forward negative, Ea_backward positive, confirming opposite signs.

Why C is correct:

• Activation energy is always positive by definition, while ΔH_forward is negative for exothermic reactions (ΔH = H_products - H_reactants < 0), yielding opposite signs per standard thermodynamics.

Why the others are wrong:

• A: Ea_forward (positive) and ΔH_backward (positive, as reverse of exothermic) have same sign, not opposite.
• B: No diagram scale provided to compare magnitudes; not enough information.
• D: ΔH_forward magnitude cannot exceed Ea_backward (always positive and larger barrier); violates energy conservation.

Final answer: C