Bond enthalpies Quiz
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5 questions, one answer each
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1. Which statement about bonds and energy is correct?
- A. Breaking bonds releases energy
- B. Making bonds absorbs energy
- C. Making bonds releases energy
- D. Both making and breaking bonds are endothermic
2. For H₂ + Br₂ → 2HBr the bond enthalpies are H–H 436, Br–Br 193 and H–Br 366 kJ mol⁻¹. What is ΔH?
- A. −103 kJ mol⁻¹
- B. +103 kJ mol⁻¹
- C. +1361 kJ mol⁻¹
- D. −732 kJ mol⁻¹
3. Why does a mean bond enthalpy calculation give a different answer from Hess's law?
- A. Bond enthalpies are measured at absolute zero
- B. Hess's law is not valid for gases
- C. Bonds are not broken in reactions
- D. Mean bond enthalpies are averages taken over many different compounds
4. In which reaction can mean bond enthalpies be used?
- A. A reaction in aqueous solution
- B. A reaction in which all species are gases
- C. A reaction that forms a solid product
- D. A reaction that forms liquid water
5. The C–H bond enthalpy is 413 kJ mol⁻¹. What is the energy to break all the bonds in one mole of CH₄?
- A. 413 kJ
- B. 826 kJ
- C. 1652 kJ
- D. 2065 kJ