The enthalpy of hydration of `Cr^(+2)` is `-460` kcal `mo1^(-1)` In the absence of `CFSE` the value for `DeltaH=-424` kcal `mo1^(-1)` What is the value of `Delta_(0)` for `[Cr(H_(2)O)_(6))]^(2+)` .

Options

A. `60kcal "mole"^(-1)`
B. `-60kcal "mole"^(-1)`
C. `25.7 kcal "mole"^(-1)`
D. `-25.7kcal "mole"^(-1)`

Answer

a

Explanation

`Cr = 3d^(5)4s^(1) , Cr^(+2) = 3d^(4)` Structure is `(t_(2g)3e_(g)1)`
`CFSE (-0.4 xx 3 + 0.6)Delta_(0) = - 0.6 Delta_(0))`
`- 0.6 Delta_(0) = (- 460) - (-424) = - 36k cal mo1^(-1)`
`Delta_(0) = (-36)/(-0.6) = 60 kcal "mole"^(-1)`
` 60 xx 350cm^(-1) = 21000cm^(1-)`
`(1 kcal mo1^(-1) = 350cm^(-1))` .