The bond dissociation energies of X2, Y₂ and XY are in the ratio of 1 : 0.5 : 1. ∆H for the formation of XY is – 200 kJ mol–1. The bond dissociation energy of X2 will be (NEET 2018)

Let bond dissociation energies of 2 2 X ,Y ,XY be x kJ / mol,0.5x kJ / mol, x kJ / mol respectively. 2 2 1 1 X Y XY; H 200kJ / mol 2 2 → reactant product H H H 1 1 H x 0.5 x 1 x 2 2 200 0.5x 0.25x x 199.75 0.25x x 799 800 x x >> >> >> bond dissociation energy of 2 X = x 800 kJ / mol