Question detail
Using the supplied average bond energies, what is the energy transferred for H2 + Cl2 -> 2HCl in Reaction profiles?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Exothermic and endothermic reactions
Question
- A. -184 kJ, exothermic
- B. 184 kJ, endothermic
- C. 0 kJ, no net energy change
- D. Incorrect bond-energy interpretation 4
Answer
The correct option is -184 kJ, exothermic.
Explanation
The correct option is -184 kJ, exothermic. Bonds broken: 1 × 436 + 1 × 242 = 678 kJ. Bonds formed: 2 × 431 = 862 kJ. Energy transferred = 678 - 862 = -184 kJ. The sign shows the reaction is exothermic. This supports the approved objective to draw a simple reaction profile for an exothermic reaction and keeps bond breaking separate from bond making in Reaction profiles.
Common mistake
Mislabeling Reaction Profiles
Students often label the energy change in an exothermic reaction profile incorrectly, indicating that energy is absorbed instead of released.
Remember that in an exothermic reaction, energy is released to the surroundings, so the products should be at a lower energy level than the reactants.
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