The bond dissociation enthalpy of \( X_2 \) \( \Delta H^\circ_{\text{bond}} \) calculated from the given data is ________ \( \text{kJ mol}^{-1} \). (Nearest integer)
\( \mathrm{M^+X^- (s) \rightarrow M^+ (g) + X^- (g)} \) \( \Delta H^\circ_{\text{lattice}} = 800 \, \text{kJ mol}^{-1} \)
\( \mathrm{M (s) \rightarrow M (g)} \) \( \Delta H^\circ_{\text{sub}} = 100 \, \text{kJ mol}^{-1} \)
\( \mathrm{M (g) \rightarrow M^+ (g) + e^-}(g) \) \( \Delta H^\circ_{i} = 500 \, \text{kJ mol}^{-1} \)
\( \mathrm{X (g) + e^- (g) \rightarrow X^- (g)} \) \( \Delta H^\circ_{\text{eg}} = -300 \, \text{kJ mol}^{-1} \)
\( \mathrm{M (s) + \tfrac{1}{2} X_2 (g) \rightarrow M^+X^- (s)} \) \( \Delta H^\circ_{f} = -400 \, \text{kJ mol}^{-1} \)
[Given: \( \mathrm{M^+X^-} \) is a pure ionic compound and \( X \) forms a diatomic molecule \( X_2 \) in gaseous state]
