Interpreting Energy Profile Diagram

Steps:

• Identify reactants and products energy levels on the diagram's y-axis.
• Measure vertical difference between products and reactants for ΔH.
• Locate labeled points: X as peak height from reactants (activation energy), Y as overall energy change, Z as possible heat release.
• Match labels to standard definitions: ΔH is enthalpy change between initial and final states.

Why B is correct:

• ΔH is defined as the enthalpy difference between products and reactants, matching Y as the net vertical drop or rise in the profile.

Why the others are wrong:

• A: Without diagram details, cannot confirm if products are lower than reactants for exothermic reaction.
• C: Z likely labels a different feature, like bond energy, not specifically energy released.
• D: X typically represents activation energy (hump height), not overall ΔH.

Final answer: B