Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

When gaseous phosphorus pentachloride is heated, it breaks down to form gaseous phosphorus trichloride and chlorine. The table lists the bond energies. Bond energies: $\text{P-Cl}$ (in both chlorides): $330\,\text{kJ mol}^{-1}$ $\text{Cl-Cl}$: $242\,\text{kJ mol}^{-1}$ What is the enthalpy change for the decomposition of $\text{PCl}_5$ into $\text{PCl}_3$ and $\text{Cl}_2$?

  • A$-418\,\text{kJ mol}^{-1}$
  • B$-88\,\text{kJ mol}^{-1}$
  • C$+88\,\text{kJ mol}^{-1}$
  • D$+418\,\text{kJ mol}^{-1}$

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