lowest to highest vapor pressure?
what are they ranked lowest to highest in vapor pressure?
H2 HBr HCl and HF
- 1 decade agoFavorite Answer
HF, HBr, HCL, H2
The two factors that determine vapor pressure are:
1. intermolecular forces
Since temperature is assumed constant, the intermolecular forces is what is important. The strength of forces are arranged in reverse above. The stronger the intermolecular force, the more the molecules hold on to each other, and the less the vapor pressure is.
H2 is not polar at all, so it has only has van der waals forces which are supppper weak!
Then HBR, HCL, and HF are polar, so they have attraction to each other, and are slightly more stable.
The heavier the molecule the harder it is for it to lift out of the liquid, so the less vapor pressure. so the lighter the molecule, the higher the vapor pressure. F is the lightest, then CL, then Br.
However! here is the exception! HF can form hydrogen bonds with itself. The requirements for hydrogen bonds is having an H attatched to a super electronegative molecule. F is the most electronegative of all, so it can form hydrogen bonds where as Cl and Br cant, making HF have the most intermolecular forces, and therefor the least vapor pressure
Hope this helped!!Source(s): http://www.ausetute.com.au/intermof.html http://en.wikipedia.org/wiki/Hydrogen_fluoride look under structure