Question

$H_{2}S<H_{2}Se<H_{2}Te<H_{2}O$ This is the correct boiling point order. If true enter 1 else 0.

• A. 1

Answer 1

Answer: (A)

True (1)

Higher BP`s mean higher forces (because more thermal energy needed to separate the molecules in liquid state) Even though Sulfur is more electronegative than Se or Te (so you would expect a higher dipole moment and so higher attractive forces between molecules) the size of the molecules is a bigger factor in their interactions. More energy is needed simply because the molecules of the hydrides get bigger as you go down the Group.
Oxygen is so much more electronegative that the molecules have H-bonding in water. This give rise to almost a different (and higher) order of intermolecular force, which gives rise to such a high BP in water.