Question

let B.E. of x₂ , y₂ & xy are x kJ mol^–1 , 0.5x kJ mol–¹ and x kJ mol^–1 respectively
$$\begin{gathered} \frac{1}{2}{X}_2+\frac{{\displaystyle 1}}{{\displaystyle 2}}{Y}_2\to XY ;∆H=-200 kJ mo{l}^{-1} \\ ∆H=-200=\sum _{}^{}(B.E{)}_{Reac\tan t}-(B.E{)}_{Product} \\ =\left[\frac{1}{2}\left(X\right)+\frac{{\displaystyle 1}}{{\displaystyle 2}}(0.5X)\right]-\left[1\times \left(X\right)\right] \end{gathered}$$
B.E of X₂ = x = 800 kJ mol^–1