Exothermic Reactions and Bond Energies

Steps:

• Reaction X releases thermal energy, indicating an exothermic process.
• Exothermic reactions occur when energy released from forming new bonds exceeds energy absorbed to break existing bonds.
• Bond breaking requires energy input; bond forming releases energy.
• Thus, for exothermic, energy to break bonds is less than energy released when bonds form, matching option D.

Why D is correct:

• Exothermic reactions release net energy because bond formation releases more energy than bond breaking requires, per the bond energy definition where ΔH = energy to break - energy from forming < 0.

Why the others are wrong:

• A: Describes endothermic profile (more energy to break than released) but question specifies energy given out.
• B: Describes exothermic profile but incorrectly labels it endothermic.
• C: Labels correctly as exothermic but describes endothermic profile (more energy to break than released).

Final answer: D