Chemistry · THERMODYNAMICS

Using the bond enthalpies: \( \Delta_{\text{bond}}H^\ominus(\text{N}\equiv\text{N}) = 946\text{ kJ mol}^{-1} \), \( \Delta_{\text{bond}}H^\ominus(\text{H}-\text{H}) = 435\text{ kJ mol}^{-1} \), and mean bond enthalpy of \( \text{N}-\text{H} = 389\text{ kJ mol}^{-1} \), the standard enthalpy change for \( \text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightarrow 2\text{NH}_3(\text{g}) \) is:

1. -83 kJ mol\( ^{-1} \)
2. -166 kJ mol\( ^{-1} \)
3. +166 kJ mol\( ^{-1} \)
4. +83 kJ mol\( ^{-1} \)