Question

The correct order of boiling points of hydrogen halides is: 

• A. \( HF < HCl < HBr < HI \)
• B. \( HI < HBr < HCl < HF \)
• C. \( HCl < HBr < HI < HF \)
• D. \( HBr < HCl < HI < HF \)

Hint:

Hydrogen fluoride (HF) has an anomalously high boiling point due to strong hydrogen bonding. Other hydrogen halides follow the trend based on Van der Waals forces.

Answer 1

The Correct Option is B

Step 1: Understanding Boiling Point Trends in Hydrogen Halides 
The boiling point of a compound is influenced by intermolecular forces, including: - Van der Waals forces: Increase with molecular size. - Hydrogen bonding: Strongest in HF due to high electronegativity of fluorine. 

Step 2: Analyzing the Boiling Points 
1. **Hydrogen Fluoride (HF):** Exhibits strong hydrogen bonding, leading to an exceptionally high boiling point. 2. **Hydrogen Chloride (HCl), Hydrogen Bromide (HBr), and Hydrogen Iodide (HI):** These molecules experience only Van der Waals forces, which increase with molecular mass. Since iodine is the largest halogen, HI has the weakest Van der Waals forces among them, leading to the lowest boiling point, followed by HBr, then HCl. 

Step 3: Establishing the Order 
From experimental data, the boiling points of hydrogen halides follow the order: \[ HI<HBr<HCl<HF. \] 

Step 4: Conclusion 
Thus, the correct order of boiling points is: \[ \boxed{HI<HBr<HCl<HF}. \]