1

### AIPMT 2011 Mains

Which of the following structures is the most preferred and hence of lowest energy for SO3?
A
B
C
D

## Explanation

has maximum number of covalent bonds.
2

### AIPMT 2011 Prelims

The pairs of species of oxygen and their magnetic behavior are noted below. Which of the following presents the correct description?
A
O$_2^ -$, O$_2^{2 - }$ - Both diamagnetic
B
O+, O$_2^{2 - }$ - Both paramagnetic
C
O$_2^{ + }$, O2 - Both paramagnetic
D
O, O$_2^{2 - }$ - Both paramagnetic

## Explanation

$O_2^+$ and $O_2$ are paramagnetic in nature as they contain one and two unpaired electrons respectively.
3

### AIPMT 2011 Prelims

The correct order of increasing bond length of C $-$ H, C $-$ O, C $-$ C and C$=$C is
A
C $-$ H < C$=$C < C $-$ O < C $-$ C
B
C $-$ C < C$=$C < C $-$ O < C $-$ H
C
C $-$ O < C $-$ H < C $-$ C < C$=$C
D
C $-$ H < C $-$ O < C $-$ C < C$=$C

## Explanation

Increasing order of bond length is

$\mathop {C - H}\limits_{107\,pm} < \mathop {C = C}\limits_{134\,pm} < \mathop {C - O}\limits_{141\,pm} < \mathop {C - C}\limits_{134\,pm}$
4

### AIPMT 2011 Prelims

Which of the two ions from the list given below that have the geometry that is explained by the same hybridization of orbitals, NO$_2^ -$. NO$_3^ -$, NH$_2^ -$, NH$_4^ +$, SCN$-$?
A
NO$_2^ -$ and NO$_3^ -$
B
NH$_4^ +$ and NO$_3^ -$
C
SCN$-$ and NH$_2^ -$
D
NO$_2^ -$ and NH$_2^ -$

## Explanation

Ions Hybridisation
$NO_2^-$ $sp^2$
$NO_3^-$ $sp^2$
$NH_2^-$ $sp^3$
$NH_4^+$ $sp^3$
$SCN^-$ sp