1

### AIPMT 2007

In which of the following pairs, the two species are isostructural?
A
SO${_3^{2 - }}$ and NO${_3^{ - }}$
B
BF3 and NF3
C
BrO${_3^{ - }}$ and XeO3
D
SF4 and XeF4

## Explanation

Hybridisation of Br in BrO3 :

= ${1 \over 2}\left( {7 + 0 - 0 + 1} \right)$ = 4

Four hybrid orbital means sp3 hybridisation.

Hybridisation of Xe in XeO3 :

= ${1 \over 2}\left( {8 + 0 - 0 + 0} \right)$ = 4

Four hybrid orbital means sp3 hybridisation.

Thus, both BrO3 and XeO3 are sp3 hybridised with three bond pairs of electrons and one lone pair of electrons and results in trigonal pyramidal shape.

2

### AIPMT 2006

Which of the following species has a linear shape?
A
O3
B
NO2$-$
C
SO2
D
NO2+

## Explanation

Due to sp hybridisation of N+, NO2+ ion has linear shape.
3

### AIPMT 2006

Which of the following is not isostructural with SiCl4 ?
A
NH4$-$
B
SCl4
C
SO42$-$
D
PO43$-$

## Explanation

SiCl4, NH4+, SO42- and PO43- ions are the examples of molecules/ions which are of AB4 type and have tetrahedral structure. SCl4 is AB4(lone pair) types species. Although the arrangement of five sp3d hybrid orbitals in space is trigonal bipyramidal, due to the presense of one lone pair of electron in the basal hybrid orbital, the shape of AB4(lone pair) species gets distorted and becomes distorted tetrahedral or see-saw.
4

### AIPMT 2006

Which of the following is not a correct statement?
A
Multiple bonds are always shorter than corresponding single bonds.
B
The electron-deficient molecules can act as Lewis acids.
C
The canonical structures have no real existence.
D
Every AB5 molecule does in fact have square pyramid structure.

## Explanation

AB5 molecule has generally trigonal bipyramidal structure. Sometimes due to presence of lone pair of electrons the structure gets distorted.