[ahawk1]

what am i doing wrong?
For the reaction between methane and chlorine shown below, ΔH° = –305.2 kJ.
CH4 (g) + 3 Cl2 (g) → CHCl3 (g) + 3 HCl (g)
Use the data in the table below to estimate the average C–Cl bond energy.
Type of bond Average bond energy (kJ/mol)
C–H 415
Cl–Cl 242
H–Cl 432
-305.2=[3*x+415+3*432]-[4*415+3*242] i get x=123.266 and the correct answer is 326.7 kJ/mol can u explain the correct way to do this and tell me why it is so?
i thought ΔH°=products-reactants

[Astrokel]

i thought ΔH°=products-reactants

Nope, that is only true for formation.

http://www.webchem.net/notes/how_far/enthalpy/enthalpy_diagrams.htm

[ahawk1]

i thought ΔH°=products-reactants

Nope, that is only true for formation.

http://www.webchem.net/notes/how_far/enthalpy/enthalpy_diagrams.htm

thanks a lot!!!!