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Question

Question: The thermal stability of the hydrides of group 15 follows the order :...

The thermal stability of the hydrides of group 15 follows the order :

A

NH3< PH3< AsH3< SbH3< BiH3

B

NH3> PH3> AsH3> SbH3> BiH3

C

PH3> NH3> AsH3> SbH3< BiH3

D

AsH3< PH3> SbH3> BiH3> NH3

Answer

NH3> PH3> AsH3> SbH3> BiH3

Explanation

Solution

Down the group the X–H bond length increases with increase in size of atom. So bond dissociation energies decrease and thererfore, thermal stability decrease. Hence the correct decreasing order is NH3 > PH3 > AsH3 > SbH3 > BiH3.