Question

Fifth group elements form hydrides to type `AH_(3)`. The hydrides have a lone pair of electrons. The hydries are reducing in nature and the reducing power is related to the stability of A-H bonds. The hydrides are covalent and low boiling. Their boiling points depends on their ability to from hydrogen bond and their molecular size which decide the intermolcular forces in the hydrides .
Reducing power of V-group hydrides are in order :
A. `NH_(3) gt PH_(3) gt Ash_(3) gt Sbh_(3) gt BiH_(3)`
B. `BiH_(3) gt SbH_(3) gt Ash_(3) gt PH_(3) gt NH_(3)`
C. `PH_(3) gt NH_(3) gt Ash_(3) gt SbH_(3) gt BiH_(3)`
D. `BiH_(3) gt SbH_(3) gt Ash_(3) gt NH_(3) gt PH_(3)`

Answer 1

Correct Answer - B
A-H bond energy derceases with increase in size of A. Hence Bi-H bond radily breaks to make it the best reducer and the reducing power decreases with decrease of size of A.