Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

Hess’ law can be applied to work out enthalpy changes by using average bond energies, as the diagram indicates. U represents the total of the reactants’ average bond energies, while V represents the total of the products’ average bond energies. For the reaction shown below, which expression would produce a value for W, the enthalpy change of combustion of methane? $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$

  • A$U - V$
  • B$U + V$
  • C$2(U - V)$
  • D$V - U$

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