Question

Explain the following situations:
(i) In the structure of HNO₃ molecule, the N—O bond (121 pm) is shorter than N—OH bond (140 pm).

(ii) SF₄ is easily hydrolysed whereas SF₆ is not easily hydrolysed.

(iii) XeF₂ has a straight linear structure and not a bent angular structure.

Answer 1

As a result of resonance, N–O bond length is average of single bond and double bond whereas N–O H bond has purely single bond character. Therefore, N–O bond is shorter than N–OH bond in HNO_3^.

(ii) S atom in SF₄ is not sterically protected as it is surrounded by only four F atoms, so attack of H₂O molecules can take place easily and hence hydrolysis takes place easily. In contract, in SF₆, S is sterically protected by six F atoms. Therefore does not allow H₂O molecules to attack S atoms. As a result of this, SF₆ does not undergo hydrolysis.

(iii) In XeF₂, Xe is sp³d hybridised having 2 bond pair and 3 lone pair of electrons. The presence of 3 lone pair of electrons in Xe F₂ at equidistance to have minimum repulsion is responsible for its linear structure.