The unusually high boiling point of water compared with formaldehyde which also contains hydrogen and oxygen also is because of water's ability to do what?

1 Answer
Jan 29, 2016

The high boiling point of water is due to the propensity of the water molecule to hydrogen-bond.


Hydrogen bonding occurs where the hydrogen atom is covalently bound to a strongly electronegative element such as oxygen or fluorine. The electronegative atom polarizes electron density away from the bond with the result that the oxygen acquires a partial negative charge, and the hydrogen acquires a partial positivie charge, i.e. #""^(delta+)H-O^(delta-)-H^(delta+)#.

These dipoles can align in solution, which acts as attractive intermolecular force, and is held to be responsible for the unusually high boiling point of water (compare the boiling points of #H_2Se#, and #H_2S#, both gases as room temperature). The enhanced boiling point is also observed fro hydrogen fluoride, #HF#, which boils at #19.5# #""^@C# (compare boiling points of #HCl#, and #HBr#).