Question

Statement I: The boiling points of the following hydrides of group 16 elements increases in the order:

H₂O < H₂S < H₂Se < H₂Te

Statement II: The boiling points of these hydrides increase with increase in molar mass.

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

Options

• Both statement I and statement II are incorrect.

• Statement I is correct but statement II is incorrect.

• Statement I is incorrect but statement II is correct.

• Both statement I and statement II are correct.

Answer 1

Both statement I and statement II are incorrect.

Explanation:

The boiling points of group 16 hydrides actually do not increase in the order H₂O < H₂S < H₂Se < H₂Te. Water (H₂O) has an abnormally high boiling point due to strong intermolecular hydrogen bonding, so it boils at a much higher temperature than H₂S despite having much lower molar mass. For the rest (H₂S, H₂Se, H₂Te), boiling points increase with increasing molar mass due to stronger van der Waals forces. Therefore, Statement I is incorrect, as it wrongly states the boiling point order, but Statement II is correct because boiling points increase with molar mass except for the anomaly of water at the start of the group.