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Calculate the bond enthalpy of the O - H...

Calculate the bond enthalpy of the `O - H` bond using the following thermochemical equations:
`H_(2) O (g) rarr H (g) + OH (g)`, `Delta_(bond H^(@) = 502 kJ`
`OH (g) rarr (g) + O (g),` `Delta_(bond) H^(@) = 427 kJ`

A

`502 kJ`

B

`464.5 kJ`

C

`427 kJ`

D

`929 kJ`

Text Solution

Verified by Experts

The correct Answer is:
B
In polyatomic molecules such as `H_(2) O`, bond enthalpy (better called average bond enthalpy) is the average of the bond dissociation enthalpies. Thus,
`Delta_(O - H) H^(@) = (502 + 527)/(2) = 464.5 kJ`
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