Question

Which one has the lowest b.p. based on their polarities? H2O, CH4, SeCl2, CHCl3?

I'm confused on how to even find polarity in the first place which is what I think is stopping me from being able to answer the question. Any help would be greatly appreciated!

Answer 1

http://www.youtube.com/watch?v=es78s3y1wcI maybe this'll help...

Answer 2

Highly electronegative atoms will draw the electrons to their side of the molecule. If you take a look at ptable.com, you can switch to a view of the elements by their electronegativity. The gist of it is, that you'll get more electronegative as you approach the upper-right hand corner of the PTE.

Additionally, you'll want to take three elements in particular into account because of their role in hydrogen bonding. They are, N, O and F.

Whenever a molecule is very lopsided, or exhibits H-bonds, the attraction between those molecules will be strong. The stronger that attraction, the more energy it will take to overcome them, hence, increased an increased boiling point.

Long non-polar molecules will also demonstrate similar properties such that a longer non-polar molecule substance will have a higher boiling point than a shorter one.

Anyhow, that was pretty long-winded, but I hope it helps.