Question

Statement-I : The boiling point order is \( \mathrm{HF>HI>HBr>HCl} \)
[2mm] Statement-II : The melting point order is : \( \mathrm{HI>HF>HBr>HCl} \)

• A. Both statements are correct.
• B. Both statements are incorrect.
• C. Statement I is correct while Statement II is incorrect.
• D. Statement I is incorrect while Statement II is correct.

Hint:

Hydrogen bonding dominates {boiling point}, while {molecular mass and packing} play a major role in melting point.

Answer 1

The Correct Option is A

Concept:
Boiling point and melting point depend on the strength of intermolecular forces.

Hydrogen bonding
significantly increases boiling point.
Van der Waals forces
increase with molecular mass and size.
Melting point also depends on crystal packing
in the solid state.
Statement-I Analysis (Boiling Point):


HF forms strong intermolecular hydrogen bonds
, hence has the highest boiling point.
For remaining hydrogen halides, boiling point increases with molecular mass: \[ \mathrm{HI>HBr>HCl} \]
Thus, the boiling point order: \[ \mathrm{HF>HI>HBr>HCl} \] Statement-I is correct
. Statement-II Analysis (Melting Point):


Melting point depends on lattice strength and packing efficiency.
HI has the highest molar mass and strongest dispersion forces, giving the highest melting point.
HF, despite hydrogen bonding, packs less efficiently than HI.
Thus, the melting point order: \[ \mathrm{HI>HF>HBr>HCl} \] Statement-II is also correct
.
Final Conclusion:
Both Statement-I and Statement-II are correct
.