From the following data at `25^(@)C`, calculate the bond energy of O – H bond:
(i) `H_(2)(g) to 2H(g), Delta H_(1) = 104.2 kcal`
(ii) `O_(2)(g) to 2O(g), DeltaH_(2) = 118.4 kcal `
(iii) `H_(2)(g) + 1/2 O_(2)(g) to H_(2)O(g), Delta H_(3) = -57.8 k cal`

Answer

`110.6 kcal`

Explanation

For reaction (iii) `: Delta_(r) H^(@) =Delta _(H-H) H^(@) + (1)/(2) Delta _(O=O) H^(@) - 2Delta _(O-H) H^(@)`
`- 57.8 =104.2 + ( 1)/(2) xx 118.4 - 2 xx B.E. ( O-H)`
or `2 xx B.E. ( O-H) = 221. 2 kcal` or ` B.E. ( O-H) = 110.6 kcal`