If `x_(1),x_(2) and x_(3)` are enthalpies of H-H , O=O and O-H bonds respectively , and `x_(4)` is the enthalpy of vaporisation of water , estimate the standard enthalpy of combustion of hydrogen:
A. `x_(1) + (x_(2))/(2) - 2x_(3) + x_(4)`
B. `X_(1) + (x_(2))/(2) - 2x_(3) - x_(4)`
C. `x_(1) + (x_(2))/(2) - x_(3) + x_(4)`
D. `2x_(3) - x_(1) - (x_(2))/(2) - x_(4)`

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1 Answers

Correct Answer - B
`H_(2)+1/2 O_(2) rarr H_(2)O(l)`
`DeltaH=x_(1)+x_(2)/2-2x_(3)`
`H_(2)O(l) rarr H_(2)O(g)`
`DeltaH=x_(1)+x/2-2x_(3)-x_(4)`

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