1
MCQ (Single Correct Answer)

### AIPMT 2015

In which of the following pairs, both the species are not isostructural ?
A
Diamond, Silicon carbide
B
NH3, PH3
C
XeF4, XeO4
D
SiCl4, PCl4+

## Explanation

2
MCQ (Single Correct Answer)

### AIPMT 2014

Which one of the following species has plane triangular shape ?
A
N3
B
NO3$-$
C
NO2$-$
D
CO2

## Explanation

Hybridisation of N3 is sp, so it is linear in shape.

Hybridisation of NO3 is sp2, so it is plane triangular in shape.

Hybridisation of NO2 is sp, so it is linear in shape.

Hybridisation of CO2 is sp, so it is linear in shape.
3
MCQ (Single Correct Answer)

### AIPMT 2014

Which of the following molecules has the maximum dipole moment ?
A
CO2
B
CH4
C
NH3
D
NF3

## Explanation

Even though for CO2 and CH4 the C - O and C - H bonds are polar but due to their symmetrical structure they have zero dipole moment.
In NH3, H is less electronegative than N and hence the dipole moment of each N-H bond is towards N which is in the similar direction of lone pair but for NF3 the dipole moment of N-F bond is in opposite direction of lone pair which reduce the value of net dipole moment.
4
MCQ (Single Correct Answer)

### NEET 2013

Identify the correct order of solubility in aqueous medium.
A
Na2S > CuS > ZnS
B
Na2S > ZnS > CuS
C
Cus > ZnS > Na2S
D
ZnS > Na2S > CuS

## Explanation

Water is a polar compound so the salt which is more polar or having more ionic character will be more soluble in it. According to Fajan's rule, ionic character of compound increases with increase in the size of cation. Now, among the given compounds, the size of cations are in the order as follows :

Na+ > Zn2+ > Cu2+

Thus, the order of ionic character and the solubility order in aqueous medium is as follows :

Na2S > ZnS > CuS

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NEET

Class 12