Question detail
For The energy change of reactions (HT only), use bond energies to answer this exam-check check: what is the energy transferred for H2 + I2 -> 2HI?
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. -9 kJ, exothermic
- B. 9 kJ, endothermic
- C. 0 kJ, no net energy change
- D. 184 kJ, endothermic
Answer
The correct option is -9 kJ, exothermic.
Explanation
The correct option is -9 kJ, exothermic. Bonds broken: 1 × 436 + 1 × 151 = 587 kJ. Bonds formed: 2 × 298 = 596 kJ. Energy transferred = 587 - 596 = -9 kJ. The sign shows the reaction is exothermic. This exam-check question supports the approved objective to (HT only) Explain that bond energies can be used to calculate energy released when bonds form and keeps bond breaking separate from bond making in The energy change of reactions (HT only).
Common mistake
Misunderstanding Bond Energies
Students often confuse bond energies with the overall energy change of a reaction, thinking that bond energies alone determine whether a reaction is exothermic or endothermic.
Emphasize that bond energies are used to calculate the energy released when bonds form, and this must be compared to the energy needed to break bonds to determine the overall energy change.
Related flashcards
Flashcard 1 of 5
Related practice questions
Question 1 of 5
Choose an answer, get feedback, then move sideways through the set.