The standard heat of formation values of `SF_(6)(g), S(g)`, and `F(g)` are `-1100, 275`, and `80 kJ mol^(-1)`, respectively. Then the average `S-F` bond enegry in `SF_(6)`

Options

A. 309kJ
B. 315kJ
C. 320kJ
D. 300kJ

Answer

A

Explanation

Given `S(s)+3F_(2)(g)toSF_(6)(g),DeltaH=-1100kJ`…….i
`S(s)toS(g),DeltaH=275kJ`………ii
`1//2F_(2)(g)toF(g), DeltaH=80kJ` ………iii
to get `SF_(6)(g)toS(g)+6F(g)` we can proceed as
(ii) + `6xx` (iii) -(i)
`:.SF_(6)(g)toS(g)+6F(g),DeltaH=1855kJ`
Thus average bond energy for S-F bond `=1855/6=309.106kJ`