Question

The correct decreasing order of boiling points of hydrogen halides is:

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

Hint:

Boiling points of hydrogen halides depend on hydrogen bonding and molecular weight.

Answer 1

The Correct Option is C

The boiling points of hydrogen halides vary due to differences in intermolecular forces. Let's analyze the given hydrogen halides (HF, HCl, HBr, HI) and determine their boiling points based on their molecular structures. 

1. Hydrogen Fluoride (HF): HF has the highest boiling point among the hydrogen halides because it engages in extensive hydrogen bonding. Hydrogen bonding is a strong intermolecular force that significantly increases the boiling point.
2. Hydrogen Iodide (HI), Hydrogen Bromide (HBr), and Hydrogen Chloride (HCl): For these halides, the boiling points are influenced by the molecular weight and the strength of van der Waals dispersion forces. As the molecular size and weight increase from HCl to HI, the boiling point also increases due to stronger van der Waals forces. Thus, the order is HI > HBr > HCl.

Therefore, the correct order of decreasing boiling points for hydrogen halides, considering these intermolecular forces, is:

\(HF > HI > HBr > HCl\)

The correct answer is \(HF > HI > HBr > HCl\) because the extensive hydrogen bonding in HF makes it have a higher boiling point than the others. Among the remaining halides, the boiling points increase from HCl to HI due to increasing molecular weight and dispersion forces.

Answer 2

Hydrogen fluoride (HF) has the highest boiling point among hydrogen halides due to strong hydrogen bonding. The remaining hydrogen halides (HCl, HBr, HI) exhibit increasing boiling points with increasing molecular weight and van der Waals forces. Thus, the correct order is:

\(HF > HI > HBr > HCl\)

This is because HF forms strong intermolecular hydrogen bonds, while other halides rely on weaker van der Waals interactions. HI, being the heaviest, has stronger van der Waals forces than HBr and HCl.