Which gas has the greater degree of intermolecular force: ammonia, #NH_3(g)#; or phosphine, #PH_3(g)#?

1 Answer
anor277
May 21, 2016

Phosphine, #"b.p. "-87.7# #""^@C#; ammonia, #"b.p. "-33.3# #""^@C#;

Explanation:

Given the boiling points, CLEARLY, ammonia, #NH_3#, has the greatest degree of intermolecular bonding. How do we rationalize this? The obvious discriminant is hydrogen bonding. There is little electronegativity difference between phosphorus and hydrogen, and yet a large difference exists between nitrogen and hydrogen.

The #N-H# bond is strongly polar on this account. The result is that the ammonia participates in intermolecular hydrogen bonding, which is a potent intermolecular force.

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