The standard molar enthalpies of formation of `IF_(3)(g)" and " IF_(5)(g)` are -470 kJ and -847 kJ, respectively. Valence shell electron-pair repulsion theory predicts that `IF_(3)(g)` is square pyramidal in shape in which all I-F bonds are equivalent while `IF_(3)(g)` is T-shaped (based on trigonal-bipyramial geometry) in which I-F bonds are of different lengths. It is observed that the axial I-F bonds in `IF_(3)` are equivalent to the I-F bonds in `IF_(5)`. Calculate the equitorial I-F bond strength `("in" "kJ"//"mol")` in `IF_(3)`.
Some other informations given are :
`I_(2)(s)toI_(2)(g)," "Delta H=62 kJ`
`F_(2)(g)to 2F(g)," "Delta H =155 kJ`
`I_(2)(g)to 2I(g)," "Delta H =149 kJ`

Answer

272