Using bond energies, what is the overall energy change for a reaction where bond breaking requires 800 kJ/mol and bond forming releases 950 kJ/mol?

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Question

Using bond energies, what is the overall energy change for a reaction where bond breaking requires 800 kJ/mol and bond forming releases 950 kJ/mol?

Accepted Answer

−150 kJ/mol, exothermic — Energy change = energy in (breaking) − energy out (forming) = 800 − 950 = −150 kJ/mol. A negative value indicates an exothermic reaction. Option A reverses the sign. Option B incorrectly adds the values. Option C also incorrectly adds the values and gives the wrong sign.

Answer

+150 kJ/mol, endothermic

Answer

+1750 kJ/mol, endothermic

Answer

−150 kJ/mol, exothermic

Answer

−1750 kJ/mol, exothermic

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