AFFAR B.

asked • 02/28/20

What are the most significant intermolecular forces that affect solubility?

Hazbar K.

Polarity affects solubility due to the creation of dipoles between molecules. Assuming that the solvent and solute are both polar, the strongest IMF would be the ionic-ionic force (NaCl for example). Hydrogen bonding is second strongest (polar with strong dipole-dipole attraction between Hydrogen and electronegative atom such as F, N, O, etc. Third strongest also Dipole-Dipole (Van der Waals Dipole Interaction) which also relies on electronegative atoms (F,N, O) forming a dipole-dipole force, except instead of bonding with hydrogen, another atom is bonded, such as carbon. The difference in electronegativity compared to H-Bonding is what makes this type of IMF a bit weaker but still a strong force nonetheless. The weakest of intermolecular forces is the Van der Waals Dispersion Interaction (London Dispersion to avoid confusion with Van der Waals Dipole Interaction). London Dispersion forces are found in neutral, non-polar molecules such as your simple hydrocarbon chain. They allow neutral and non-polar molecules to attract each other. The attractive force is the weakest IMF and thus their dipole is temporary. Increasing the surface area of a molecule (for example, extending a hydrocarbon chain with only 4 carbons to one with 7 (butane to heptane), will strengthen the London dispersion dipole strength. This is the reasoning behind the fact that longer chained hydrocarbons have a higher boiling point. The longer the chain, the stronger the IMF, and thus the more heat/energy is needed to reach its boiling point.
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03/14/20

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