Chemistry 5070 · O Level · Exothermic and endothermic reactions

Exothermic and endothermic reactions — practice question

Hydrogen combines with chlorine to make hydrogen chloride. $\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})$ The enthalpy change, $\Delta H$, for this reaction may be worked out by using bond energies. Bond energies: $\text{H--H} = 436\,\text{kJ mol}^{-1}$, $\text{Cl--Cl} = 242\,\text{kJ mol}^{-1}$, $\text{H--Cl} = 431\,\text{kJ mol}^{-1}$. What is the value of $\Delta H$ for this reaction?

  • A$-247\,\text{kJ mol}^{-1}$
  • B$-184\,\text{kJ mol}^{-1}$
  • C$+184\,\text{kJ mol}^{-1}$
  • D$+247\,\text{kJ mol}^{-1}$

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