If the bond dissociation energies of `XY,X_(2)` and `Y_(2)(` all diatomic molecules `)` are in the ratio `1:1:0.5` and `Delta_(f)H` of `XY` is `-200 kJ mol^(-1)`. The bond dissociation energy of `X_(2)` will be `:`

Options

A. 100 kJ / mol
B. 200 kJ / mol
C. 300 kJ / mol
D. 800 kJ / mol

Answer

D

Explanation

Let the bond dissociation energy of `XY, X_(2) and Y_(2)` be x, x and x, kJ/ mol respectively,
`(1)/(2) X_(2)+(1)/(2) Y_(2) rarr XY, Delta H_(f)=-200" kJ/mol"`
`Delta H_("reaction")`=[(sum of bond dissociation energy of all reactants)-(sum of bond dissociation energy product)]
`=[(1)/(2) Delta H_(X_(2))+(1)/(2) Delta H_(Y_(2))-Delta H _(XY)]`
`=(x)/(2) +(0.5x)/(2)-x=-200`
`therefore x=800" kJ/mol"`