In solid `NH_(3)` each `NH_(3)` molecule has six other `NH_(3)` molecules as nearest neighbouts. `DeltaH` of sublimation of `NH_(3)` at the melting point is `30.8 kJ mol^(-1)` and the estimated `DeltaH` of sublimation in the absence of `H-` bonding is `14.4kJ mol^(-1)`. What is the strength of a hydrogen bond in solid ammonia ?
A
`6.5kJ mol^(-1)`
B
`16.5kJ mol^(-1)`
C
`5.5kJ mol^(-1)`
D
`4.5kJ mol^(-1)`
Text Solution
Verified by Experts
The correct Answer is:
C
Total strength of `H-` bond =`20.8-14.3` `=16.5kJ mol^(-1)` There are 6 nearest neighbours, but each `H-` bond involves 2 molecules. Thus, total` H-` bond `=(6)/(2)=3` `:. ` `H-` bond energy `=(16.5)/(3)=5.5kJ mol^(-1)`
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