Chemistry 9701 · AS & A Level · Group 17

Group 17 — practice question

Hydrogen chloride gas and hydrogen iodide gas do not have the same thermal stability. This difference arises because some of the covalent bonds involved in decomposition have different bond energies. Which row identifies which of the two compounds is the more stable, and provides the correct reason?

  • Ahydrogen chloride; the $\text{Cl-Cl}$ bond is stronger than the $\text{I-I}$ bond
  • Bhydrogen chloride; the $\text{H-Cl}$ bond is stronger than the $\text{H-I}$ bond
  • Chydrogen iodide; the $\text{Cl-Cl}$ bond is stronger than the $\text{I-I}$ bond
  • Dhydrogen iodide; the $\text{H-Cl}$ bond is stronger than the $\text{H-I}$ bond

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