The correct order of the boiling points of ${\mathrm{H}}_2\mathrm{O} , \mathrm{HF} , {\mathrm{NH}}_3$ is: 

1. HF > H₂O > NH₃

2. H₂O > HF > NH₃

3. NH₃ > HF > H₂O

4. NH₃ > H₂O > HF

In ${\mathrm{PO}}_4^{3-}$ ion, the formal charge on the oxygen atom of the P-O bond is : 

In ${\mathrm{NO}}_3^{-}$ ion, the number of bond pairs and lone pairs of electrons on the nitrogen atom is

1. 2, 2

2. 3, 1

3. 1, 3

4. 4, 0

Which species lacks tetrahedral geometry?

1. ${\mathrm{BH}}_4^{-}$

2. ${\mathrm{NH}}_2^{-}$

3. ${\mathrm{CO}}_3^{2-}$

4. ${\mathrm{H}}_3{\mathrm{O}}^{+}$

The number of $\mathrm{\pi }$ bonds and $\mathrm{\sigma }$ bonds in the following structure is :

1. 6, 19

2. 4, 20

3. 5, 19

4. 5, 20

The species doesn't have unpaired electrons is:

1. ${\mathrm{N}}_2^{+}$

2. ${\mathrm{O}}_2$

3. ${\mathrm{O}}_2^{2-}$

4. ${\mathrm{B}}_2$

In which of the following molecule/ion all the bonds are not equal?

1.  ${\mathrm{XeF}}_4$

2. ${\mathrm{BF}}_4^{-}$

3. ${\mathrm{C}}_2{\mathrm{H}}_4$

4. ${\mathrm{SiF}}_4$

Hydrogen bond will be strongest in : 

1. HCl

2. H₂O

3. HI

4. H₂S

If the electronic configuration of an element is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{2}4{\mathrm{s}}^2$, the four electrons that participate in the chemical bond formation will be from :

1. $3{\mathrm{p}}^6$

2. $3{\mathrm{p}}^6, 4{\mathrm{s}}^2$

3. $3{\mathrm{p}}^6, 3{\mathrm{d}}^2$

4. $3{\mathrm{d}}^2, 4{\mathrm{s}}^2$

The correct bond angle for sp² hybridization is:

1. $90°$

2. $120°$

3. $180°$

4. $109°$