Q. 143.7( 30 Votes )
Among NH3, H2O and HF, which would you expect to have highest magnitude of hydrogen bonding and why?
1. Hydrogen fluoride molecule has only straight chain of bonding whereas on the other hand water molecule which consists of two hydrogen and one oxygen atom forms a huge ring like structure.2. The hydrogen bonding in ammonia is limited because nitrogen atom possess only one lone pair of electrons. Hence, H2O has the strongest hydrogen bonded structure.
3. The strength of hydrogen bonding also depend upon the electronegativity of the element and it also depend upon the number of hydrogen atoms which are available for bonding. Among nitrogen, fluorine, and oxygen, the increasing order of their electro negativities are N < O < F.
4. Hence, the expected order of the extent of hydrogen bonding is H2O > HF > NH3. But, the actual order is H2O > HF > NH3.
5. Though the electronegativity of fluorine is greater as compared to that of oxygen, the strength of bonding in water molecule is greater as compared to the bonding in HF molecule because the HF molecule has shortage of hydrogen atoms. Hence water has more number of hydrogen atoms and thus forms a ring like structure and HF only forms a planar structure.
6. In case of ammonia, the extent of hydrogen bonding is limited because nitrogen has only one lone pair. Therefore, it cannot satisfy all hydrogens.
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