Chemistry · CHEMICAL BONDING AND MOLECULAR STRUCTURE

For water vapor, the stepwise bond dissociation enthalpies are: \( \text{H}_2\text{O}(\text{g}) \rightarrow \text{H}(\text{g}) + \text{OH}(\text{g});\ \Delta_{\text{a}}H_1^\ominus = 502\text{ kJ mol}^{-1} \) \( \text{OH}(\text{g}) \rightarrow \text{H}(\text{g}) + \text{O}(\text{g});\ \Delta_{\text{a}}H_2^\ominus = 427\text{ kJ mol}^{-1} \) What is the mean (average) \( \text{O}-\text{H} \) bond enthalpy in \( \text{H}_2\text{O} \)?

1. A
   \( 929.0\text{ kJ mol}^{-1} \)
2. B
   \( 427.0\text{ kJ mol}^{-1} \)
3. C
   \( 502.0\text{ kJ mol}^{-1} \)
4. D
   \( 464.5\text{ kJ mol}^{-1} \)