Question

Given below are two statements: Statement I: The increasing order of boiling point of hydrogen halides is HCl<HBr<HI<HF. Statement II: The increasing order of melting point of hydrogen halides is HCl<HBr<HF<HI. In the light of the above statements, choose the correct answer from the options given below:

• A. Statement I is true but Statement II is false
• B. Both Statement I and Statement II are false
• C. Both Statement I and Statement II are true
• D. Statement I is false but Statement II is true

Hint:

Boiling points follow intermolecular forces (hydrogen bonding, van der Waals). Melting points depend on crystal lattice packing, so trends may be irregular.

Answer 1

The Correct Option is A

Step 1: Boiling points. - Boiling point depends on intermolecular forces. - HF has strong hydrogen bonding → highest boiling point. - Among HCl, HBr, HI: boiling point increases with molecular mass. \[ \text{Order: HCl<HBr<HI<HF} \] So, Statement I is true.
Step 2: Melting points. - Melting point trends are irregular due to lattice packing. - Actual order: HCl<HF<HBr<HI. - Given order (HCl<HBr<HF<HI) is incorrect. So, Statement II is false. \[ \text{Correct choice: (1)} \]