What intermolecular interactions occur for #"(i) dihydrogen"#, #"(ii) acetone"#, #"(iii) propane"#, and #"(iv) ammonia"#, #"(v) water"#, and #"(vi) hydrogen fluoride"#?

Can you rank these in order of volatility?

1 Answer
anor277
Jul 22, 2017

Well, van der Waals interactions occur for each set of molecules.....

Explanation:

But van der Waals interactions are weak, and thus dihydrogen, for which ONLY dipersion forces operate, is the MOST VOLATILE of the given substances, with a normal boiling point of #-253.9# #""^@C#. Propane, which also possesses minimal intermolecular interaction, is next cab off the volatility rank.

For acetone, there is some degree of dipole-dipole interaction, in that there is some polarity in the carbonyl bond, i.e. #stackrel(delta+)C=stackrel(delta-)O#; compare the boiling point of acetone, #56# #""^@C#, with that of propane, #-42# #""^@C#, the which only has dispersion forces operating.

For ammonia, hydrogen chloride, and water a special type of dipole-dipole interaction operates, #"hydrogen bonding"#, and this occurs where hydrogen binds to a strongly electronegative element such as oxygen, or fluorine, or nitrogen. You should look up the normal boiling points of #HF# and #NH_3#, and #H_2O#, and compare them to their lower group hydrides.

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