Question

Which one of the following has the lowest boiling point?

• A. ${\mathrm{H}}_2\mathrm{O}$
• B. ${\mathrm{H}}_2\mathrm{Te}$
• C. ${\mathrm{H}}_2\mathrm{Se}$
• D. ${\mathrm{H}}_2\mathrm{S}$

Answer 1

The correct option is D

${\mathrm{H}}_2\mathrm{S}$

Explanation for the correct option

(D) ${\mathbf{H}}_{\mathbf{2}}\mathbf{S}$

Boiling point

• The boiling point of a liquid is the temperature at which the liquid's vapor pressure equals the atmospheric pressure of the liquid's surroundings.
• The boiling point is determined by ionic bonding, intermolecular interactions, molecule structure, and size.
• The type of functional group attached to the molecule has an impact on the parameters.

Boiling Point trends in group $16$ elements

• Except for water $\left({\mathrm{H}}_2\mathrm{O}\right)$, the boiling point of the group $16$ hydride increases as the molecular mass increases.
• Water is an exception owing to intermolecular hydrogen bonding between water molecules.
• Because of the existence of high electronegativity oxygen atoms, water molecules form strong hydrogen bonds.
• As a result, the boiling point of ${\mathrm{H}}_2\mathrm{O}$ is substantially higher than that of the other Hydride.
• The boiling points of group $16$ hydrides are as follows:

${\mathrm{H}}_2\mathrm{O}>{\mathrm{H}}_2\mathrm{Te}>{\mathrm{H}}_2\mathrm{Se}>{\mathrm{H}}_2\mathrm{S}$.

• Therefore, Hydrogen sulfide $\left({\mathrm{H}}_2\mathrm{S}\right)$ has the lowest boiling point.

Explanation for incorrect options

• Hydrogen sulfide $\left({\mathrm{H}}_2\mathrm{S}\right)$ has the lowest boiling point.
• Hence, all other options (A), (B), and (C) are incorrect.

Therefore, the correct option is (D) ${\mathbf{H}}_{\mathbf{2}}\mathbf{S}$.