Chemistry Question from JEE Main 2025 · 23 January, Shift 2

The bond dissociation enthalpy of $X_2$ calculated from the given data is _____ kJ mol$^{-1}$ (nearest integer).

Given:

$M^+X^-(s) \rightarrow M^+(g) + X^-(g)$, $\Delta H^\circ_{\text{lattice}} = 800 \, \text{kJ mol}^{-1}$

$M(s) \rightarrow M(g)$, $\Delta H^\circ_{\text{sub}} = 100 \, \text{kJ mol}^{-1}$

$M(g) \rightarrow M^+(g) + e^-(g)$, $\Delta H^\circ_{i} = 500 \, \text{kJ mol}^{-1}$

$X(g) + e^-(g) \rightarrow X^-(g)$, $\Delta H^\circ_{\text{eg}} = -300 \, \text{kJ mol}^{-1}$

$M(s) + \frac{1}{2} X_2(g) \rightarrow M^+X^-(s)$, $\Delta H^\circ_{f} = -400 \, \text{kJ mol}^{-1}$

$M^+X^-$ is a pure ionic compound and $X$ forms a diatomic molecule $X_2$ in the gaseous state.