1.

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)`

Answer» Correct Answer - 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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