Bond enthalpies Quiz
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5 questions, one answer each
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1. Which statement about bond enthalpies is correct?
- A. Breaking bonds is exothermic
- B. Making bonds is endothermic
- C. Breaking bonds is endothermic
- D. Bond enthalpies are always negative
2. Using C–H 413, O=O 498, C=O 805 and O–H 464 kJ mol⁻¹, what is ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O(g)?
- A. +818 kJ mol⁻¹
- B. −818 kJ mol⁻¹
- C. −2648 kJ mol⁻¹
- D. +3466 kJ mol⁻¹
3. Why do calculated enthalpy changes using mean bond enthalpies differ from experimental values?
- A. The reaction has not reached equilibrium
- B. Bond enthalpies are measured at 0 K
- C. Catalysts change the enthalpy change
- D. Mean bond enthalpies are averages and apply to gases
4. The enthalpy change for a reaction is +120 kJ mol⁻¹ and the bonds made total 1000 kJ mol⁻¹. What is the total for bonds broken?
- A. 1120 kJ mol⁻¹
- B. 880 kJ mol⁻¹
- C. −880 kJ mol⁻¹
- D. 1000 kJ mol⁻¹
5. In the reaction N₂ + 3H₂ → 2NH₃, how many moles of N–H bonds are made?
- A. 2
- B. 3
- C. 6
- D. 9