Estimate the average S-F bond energy in SF6. The standard heat of formation values of SF6(g), S(g), and F(g) are : - 1100, 275, and 80 kJ and mol-1 respectively.

Given S(s)+3F2(g)→SF6 ; ΔH=−1100kJ …(1)S(s)→S(g)                                                   ...(2)ΔH=275kJ12F2(g)→F(g)     ΔH=80kJ                          ...(3) Toget SF6(g)→S(g)+6F(g) , we can proceed as (2)+6×(3)−1SF6(g)→S(g)+6F(g); ΔH=1855kJ Thus,averagebondenergy =18556=309.17