Given below are two statements:

Statement I: The boiling point of hydrides of Group 16 elements follow the order H₂O > H₂Te > H₂Se > H₂S.

Statement II: On the basis of molecular mass, H₂O is expected to have lower boiling point than the other members of the group but due to the presence of extensive H-bonding in H₂O, it has higher boiling point.

In the light of the above statements, choose the correct answer from the options given below:

The correct answer is Both Statement I and Statement II are true.

Let us analyze both statements step-by-step:

Analysis of Statement I:

The hydrides of Group 16 elements are:

$H_{2}O$, $H_{2}S$, $H_2\mathrm{Se}$, and $H_2\mathrm{Te}$

Generally, as we move down a group, the molecular mass of the hydrides increases. An increase in molecular mass leads to an increase in molecular size, which in turn increases the strength of the intermolecular van der Waals forces. Consequently, the boiling point is expected to increase down the group in the following order:

$H_{2}S<H_2\mathrm{Se}<H_2\mathrm{Te}$

However, water ($H_{2}O$) exhibits strong intermolecular hydrogen bonding because oxygen is highly electronegative and has a small atomic size. This creates strong attractive forces between water molecules, requiring a high amount of thermal energy to break them. Thus, water has an anomalously high boiling point. The actual boiling points of these hydrides are:

• $H_{2}O$: 373 K

• $H_{2}S$: 213 K

• $H_2\mathrm{Se}$: 232 K

• $H_2\mathrm{Te}$: 269 K

Comparing these experimental values, the decreasing order of boiling points is indeed:

$H_{2}O>H_2\mathrm{Te}>H_2\mathrm{Se}>H_{2}S$

Therefore, Statement I is true.

Analysis of Statement II:

Based solely on molecular mass, $H_{2}O$ (molecular mass = 18 g/mol) is expected to have the lowest boiling point in Group 16 because it has the weakest van der Waals dispersion forces. However, due to the presence of extensive hydrogen bonding in water, it has a much higher boiling point than the rest of the group. Since the other members do not form hydrogen bonds, Statement II is true and correctly explains the anomalous behavior of water.