Analyzing Reaction Energy Profiles

Steps:

• Examine the diagram: reactants start at a higher energy level than products, indicating energy release.
• Activation energy is the peak height from reactant level to transition state.
• Enthalpy change (ΔH) is the vertical difference between reactant and product energy levels.
• Compare bond energies: exothermic reactions release more energy forming bonds than breaking them.

Why C is correct:

• Exothermic reactions have negative ΔH, where product energy is lower than reactants, matching the diagram's downward profile (ΔH = E_p - E_r < 0).

Why the others are wrong:

• A: Activation energy is the full barrier from reactants to transition state, exceeding E if E labels only part of it.
• B: Enthalpy change is the net difference between reactant and product levels, not solely E.
• D: Exothermic means energy to form bonds exceeds energy to break them, opposite of the statement.

Final answer: C