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KCET · Chemistry · p Block Elements (Group 15, 16, 17 & 18)

The correct decreasing order of boiling point of hydrogen halides is

  1. A \(\mathrm{HF}\gt\mathrm{HCl}\gt\mathrm{HBr}\gt\mathrm{HI}\)
  2. B \(\mathrm{HI}\gt\mathrm{HBr}\gt\mathrm{HCl}\gt\mathrm{HF}\)
  3. C \(\mathrm{HF}\gt\mathrm{HI}\gt\mathrm{HBr}\gt\mathrm{HCl}\)
  4. D \(\mathrm{HI}\gt\mathrm{HF}\gt\mathrm{HBr}\gt\mathrm{HCl}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\mathrm{HF}\gt\mathrm{HI}\gt\mathrm{HBr}\gt\mathrm{HCl}\)

Step-by-step Solution

Detailed explanation

HF is hydrogen bonded, thus it has highest boiling point. The remaining hydrogen halides are gaseous and their boiling points depend on the van der Waals' forces. Greater the molecule mass, greater will be the van der Waals' forces. Hence higher is the boiling point. Thus, the correct order is \(\mathrm{HF}\gt\mathrm{HI}\gt\mathrm{HBr}\gt\mathrm{HCl}\).