Bond Energy Determines Reaction Type

Steps:

• Recall that breaking chemical bonds always absorbs energy, while forming bonds always releases energy.
• Calculate net energy change: if energy released from forming bonds exceeds energy absorbed to break bonds, the reaction is exothermic.
• If energy absorbed to break bonds exceeds energy released from forming bonds, the reaction is endothermic.
• Evaluate each option against this principle to identify the accurate statement.

Why B is correct:

• Endothermic reactions have a positive ΔH, where bond-breaking energy input > bond-forming energy output, per the definition of enthalpy change.

Why the others are wrong:

• A: Bond formation always releases energy, so this ignores that fundamental process.
• C: Bond breaking absorbs energy, not releases it, contradicting basic bond energy rules.
• D: Bond breaking always requires energy input, so no energy is not needed.

Final answer: B