Question on Decreasing Order of the Boiling Points of Compounds

By Team Aakash Byju's | 16th January 2023

Hydrogen bonds are formed in many compounds e.g., H2O, HF and NH3. The boiling point of such compounds depends to a large extent on….              (Question continues)

The strength of the hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of the above compounds is :             

HF > H O > NH

H O > HF > NH

NH  > HF > H O

NH  > H O > HF

A

B

C

D

2

3

2

3

2

3

2

3

Detailed Explanation

The correct answer is  B) H  O > HF > NH  .

Arrow

2

3

The size and electronegativity of the atom affect the strength of the hydrogen bond.

O

O

H

H

H

H

O

H

H

Hydrogen Bond

Covalent Bond

Electronegativity of Hydrogen Bond

The strength of the H-bond increases with the atom's size because smaller atoms have more electronegativity.

Hydrogen Bond

96.5 pm

117 pm

Thus, the order of strength of H-bonding is H...F>H...O>H...N.

However, each H O molecule is connected to four other H O molecules via H-bonding.

2

2

But each HF molecule is only connected to two other HF molecules.

HF Molecules Bond

Hence, the decreasing order of boiling points is  H  O > HF > NH  .

2

3

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