Group 7: Halogens
Read our general notes on Risk Assessment
Why does HBr have a lower boiling point than HI?
Jenkin replies
This is to do with the intermolecular forces in the two compounds. There are no hydrogen bonds between the molecules of either compound, since Br and I are not electronegative enough to polarise the molecules sufficiently. But since HI molecules contain more electrons than HBr, there are increased van der Waals forces in HI. For the same reason HBr has a higher boiling point than HCl, but HF has a higher boiling point than HCl, HBr or HI because of hydrogen bonding.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
Rate this page or react
Share your views on this page, 1 ratings so far
, rated at 
updated: 25 January 2006
