Explain the trend

NCl3> PCl3 > AsCl3 > SbCl3 > BiCl3..on the account of d hydrolysis..

thkyu for ny help..!! :))

The trihalides of group 15 readily undergo hydrolysis ,but the products depend upon the nature of elements.

Here, Nitrogen halide (like NCl₃ ) is less stable  due to the gap in size of nitrogen and Cl-atoms. So. it easily get hydrolyzed. But as we move down the group , size of elements increases from N to Bi and so their stability with Cl-atom increases and so they 

Further, from P, As, and Sb acts as Lewis acid because they have d-orbitals which can accept electrons and so they form the  oxy chlorides with water.

Thus the reactivity decreases as we move down the group, due to the increase in stability down the group and so they can not completely hydrolyzed as Nitrogen trichloride but they hydrolyze partially.

Thus the order of reactivity during hydrolysis is :

NCl₃ > PCl₃ > AsCl₃ > SbCl₃ > BiCl₃ 

And the hydrolysis products are:

NCl₃  + 3H₂O -> NCl₃  + 3HOCl

PCl₃  +  3H₂O -> H₃ PO₃ + 3HCl

AsCl₃ +  3H₂O -> H₃ AsO₃ + 3HCl

Sb/Bi =>

 BiCl₃ + 3  -> BiO⁺Cl^- +2HCl