Question

Which molecule has the strongest intermolecular force ? • BF3 • NH3 •H2

Answer 1

Well, which material has the highest normal boiling point?

Explanation:

For `"dihydrogen"` it is `-259.2` `""^@C`

For `BF_3` it is `-100.3` `""^@C`...

And for `"ammonia"` it is `-33.3` `""^@C`...

So what has ammonia got that the other molecules ain't got in terms of the intermolecular force, the force between molecules NOT the intramolecular force the which represents bond-strength. The answer is hydrogen-bonding, the which occurs when hydrogen is bound to a strongly electronegative element such as oxygen, or nitrogen, or fluorine. The hydrides of all these elements have disproportionately high boiling points. And what is the hydride of oxygen, and what is its boiling point?

For ammonia we could represent the dipole as `stackrel(""^(-)delta)Nstackrel(""^+delta)H_3`....given this property, ammonia is a water-like solvent.....