1
MCQ (Single Correct Answer)

### AIPMT 2015

The variation of the boiling points of the hydrogen halides is in the order HF > HI > HBr > HCl.

What explains the higher boiling point of hydrogen fluoride?
A
There is strong hydrogen bonding between HF molecules.
B
The bond energy of HF molecules is greater than in other hydrogen halides.
C
The effect of nuclear shielding is much reduced in fluorine which polarises the HF molecule.
D
The electronegativity of fluorine is much higher than for other elements in the group.

## Explanation

HF forms strong intermolecular H-bonding due to high electronegativity of F. Hence, the boiling point of HF is exceptionally high. Boiling points of other hydrogen halides gradually increases from HCl to HI due to increase in the size of halogen atoms form Cl to I, which further increases the magnitude of van der Waal's forces.
2
MCQ (Single Correct Answer)

### AIPMT 2015

The stability of +1 oxidation state among Al, Ga, In and Tl increases in the sequence
A
Al < Ga < In < Tl
B
Tl < In < Ga < Al
C
In < Tl < Ga < Al
D
Ga < In < Al < Tl

## Explanation

The given elements belong to 13th group. The elements mainly exhibit +3 and +1 oxidation states. As we know, the stability of lower oxidation state i.e., +1 state, increases on moving down the group due to inert pair effect. The, stability follows the order :

Al < Ga < In < Tl
3
MCQ (Single Correct Answer)

### AIPMT 2014

Acidity of diprotic acids in aqueous solutions increases in the order
A
H2S < H2Se < H2Te
B
H2Se < H2S < H2Te
C
H2Te < H2S < H2Se
D
H2Se < H2Te < H2S

## Explanation

As the atomic size increases down the group the bond length increases and the bond strength decreases and the cleavage of E - H bond become easier thus, more will be the acidity. Thus, order of acidity will be

H2S $<$ H2Se $<$ H2Te
4
MCQ (Single Correct Answer)

### NEET 2013 (Karnataka)

Identify the incorrect statement, regarding the molecule XeO4 :
A
XeO4 molecule is square planar.
B
There are four p$\pi$ - d$\pi$ bonds.
C
There are four sp3 - p, $\sigma$ bonds.
D
XeO4 molecule is tetrahedral.

## Explanation

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