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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