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Calculate the bond energy of O-H bond in...

Calculate the bond energy of O-H bond in `H_(2)O(g)` at the standard state from the following data:
(1) `H_(2)(g) to 2H(g),DeltaH^(0)=436kJ*mol^(-1)`
(2) `(1)/(2)O_(2)(g)toO(g),DeltaH^(0)=249k*mol^(-1)`
(3) `H_(2)(g)+(1)/(2)O_(2)(g)toH_(2)O(g),DeltaH_(f)^(0)[H_(2)O(g)]=-241.8kJ*mol^(-1)`.

Text Solution

Verified by Experts

Equation (1)+equation (2)-equation (3) gives,
`H_(2)(g)+(1)/(2)O_(2)(g)-H_(2)(g)-(1)/(2)O_(2)(g)to2H(g)+O(g)-H_(2)(g),DeltaH^(0)=(436+249+241.8)kJ`
or, `H_(2)O(g)to2H(g)+O(g),DeltaH^(0)=+926.8kJ` . .. [4]
Equation (4) indicates dissociation of O-H bonds present in 1 mol of `H_(2)O(g)`. the standard enthalpy change for this process `(DeltaH^(0))=+926.8kJ`.
No. of O-H bonds present in 1 mol `H_(2)O=2` mol. Thus, energy required to break 2 mol O-H bonds=+926.8 kJ.
`therefore`Energy required to break 1 mol O-H=+463.4 kJ
So, bond energy of O-H bond`=+463.4kJ*mol^(-1)`.
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