Given, `S_((s))+3F_(2(g))rarr SF_(6),DeltaH=-1100kJ ....(1)`
`S_((s)) rarr S_((g)),DeltaH=275kJ ...(2)`
`(1)/(2)F_(2(g))rarr F_((g)), DeltaH=80kJ ..(3)`
To get `SF_(6(g))rarr S_((g))++6F_((g)),,`
we can proceed as `eq. (2)+6xxeq.(3)-eq.(1)`
`SF_(6(g))rarrS_((g))+6F_((g)),DeltaH=1855kJ`
Thus, average bond energy `=(1855)/(6)=309.17`