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Explain the nature of hydride compounds of group-15 elements. |
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Answer» Solution :All the elements of group-15 form hydrides of type EH3 where E = N, P, As, Sb or Bi. On moving down the group, the stability of hydrides decreases i.e.,` NH_3` is most stable while `BiH_(3)`is LEAST stable. This is due to decrease in the bond dissociation enthalpy of E-H bond as a result of increase in atomic size of the element. Consequently reducing CHARACTER of hydrides increases. Reducing strength: `NH_(3) lt PH_(3) lt AsH_(3) lt SbH_(3) lt BiH_(3)` Thermal stability: Thus ammonia is mild reducing agent while `BiH_3` is strong reducing agent. The basicity of the hydrides decreases down the group. `BiH_3` is least basic while `NH_3` is most basic. The high basicity of `NH_3` is due to high electronegativity and small size of NITROGEN. Order of basicity : `NH_(3) gt PH_(3) gt AsH_(3) gt SbH_(3) ge BiH_(3)` Ammonia (`NH_3`) exhibits hydrogen bonding both in solid and liquid state. Because of this it has higher melting and boiling points than that of `PH_3`. Order of boiling points : `BiH_(3) gt SbH_(3) gt NH_(3) gt AsH_(3) gt PH_(3)` 
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