Question

The compound with the lowest boiling point among the following is?

• A. $\mathrm{HF}$
• B. $\mathrm{HCl}$
• C. $\mathrm{HI}$
• D. $\mathrm{HBr}$

Answer 1

The correct option is B

$\mathrm{HCl}$

The explanation for the correct option:

Option(B):$\mathrm{HCl}$

• The temperature at which a liquid boils and turns into a vapour state is known as the boiling point of the liquid.
• The boiling point of covalent compounds generally increases with an increase in their molecular weight which is caused due to the increase in Van Der Waal’s forces of attraction among molecules.
• $\mathrm{HCl}$ is known to have the least boiling point among the hydrogen halides as it contains small dispersion intermolecular forces.

The explanation for the incorrect option:

Option(A):$\mathrm{HF}$

• $\mathrm{HF}$ usually shows the H-bonding and hence possesses a higher boiling point
• Hence, the given option does not coincide with the correct concept.

Option(C):$\mathrm{HI}$

• $\mathrm{HI}$ does not show the lowest boiling point, as it has comparatively higher intermolecular force than $\mathrm{HCl}$.
• Hence, the given option does not represent the correct concept.

Option(D):$\mathrm{HBr}$

• The compound $\mathrm{HBr}$ , also does not know to show the lowest boiling point, as it has comparatively higher intermolecular force than the $\mathrm{HCl}$.
• Thus, the given option is the incorrect one.

Hence, the compound with the lowest boiling point among the given compound is $\mathrm{HCl}$, option (B) is the correct answer.