Bond enthalpies of H2, O2 are 436kJ/mole and 498kJ/mole respectively. Calculate O–H bond enthalpy if  ΔfH0 of water is –286kJ/mole

Δ0H = HR0 − HPo*** Bonds are broken in reactants, endothermic        Bonds are formed in products, exothermicH−H +12 O= O→ H−O−H; ΔH = −286kJ−286 = +436+12498−2x2x = 436+249+286 x = 436+249+2862kJX = 485.5kJO–H bond enthalpy = 485.5kJ