chem
posted by DR BOOBB Plz HELP on .
stilll didn't get it .. .. can u plz explain in detail ... how did u get the answer.. plz plz plz plz plzp l zp
thnks
Bond enthalpy is the energy required to break a mole of a certain type of bond.
O=O = 495 kj/mol
SF = 327 kj/mol
S=O = 523 kj/mol
Use average bond enthalpies to estimate the enthalpy delta H (rxn) of the following reaction:
2SF4 + O2  2OSF4
Express your answer numerically in kilojoules.

Instead of asking me to work the problem step by step it would help if you told us what you don't understand. Not getting it doesn't tell us much. I gave you the formula.
Delta H_{rxn} = BE_{reactants}  BE_{products} =
[2*(4*SF bond)]+ (O=O bond)  [2*(4*SF bond) + (S=O bond)]= delta H_{rxn}
This is a matter of substituting those values for the bonds in the equation above to arrive at the answer. If you still don't understand, post your work showing how you arrived at the 103 value you posted earlier. 
i am getting 28 KJ .. is it rite plz chk

That isn't what I obtained when I tried it. Show your work and let me see what you are doing wrong (or if I have made an error).