Question

The bond energies of `H--H` , `Br--Br` and `H--Br` are `433,, 192` and `364KJmol^(-1)` respectively. The `DeltaH^(@)` for the reaction
`H_(2)(g)+Br_(2)(g)rarr2HBr(g)` is
A. `-261 KJ`
B. `+103 KJ`
C. `+261 KJ`
D. `-103 KJ`

Answer 1

Correct Answer - D
For reaction ,
`H_(2)(g) + Br_(2)(g) to 2HBr(g) DeltaH^(@)=?`
`DeltaH^(@) =- [(2xx` bond energy of HBr )-(bond energy of `H_(2) + ` bond energy of `Cl_(2))]`
`DeltaH^(@)=-[2xx(364)-(433+ 192)]KJ`
`=-[728-(625)] KJ =-103 KJ`