Rank CH3CH2CH2CH2CH2CH2OH, HOCH2CH2CH2OH, and CH3CH2CH2CH2OH from most soluble to least soluble in water.

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t-nez eNotes educator| Certified Educator

The degree to which a




All three of these molecules have the ability to hydrogen bond with water because of their OH groups. Number one is the most soluble because it has the shortest hydrocarbon chain and because it has two OH groups.

Number two is the next most soluble. It only has one OH group, which decreases hydrogen bonding, and it has a longer carbon chain, which tends to make it less soluble in water.

Number three also has one OH group, but it has six carbons in a chain whereas number 2 only has a four-carbon chain.

Longer carbon chains make a molecule less soluble because they are non-polar. The general rule for solubility is "like dissolves like". Solubility is a function of solute-solvent interactions, solvent-solvent interactions and solute-solute interactions. A substance is most soluble when solute-solvent interactions are the strongest of the three.  Water will hydrogen bond to itself, and hydrocarbons are attracted to each other by London dispersion forces, so solvent-solvent and solute-solute interactions are stronger than solute-solvent interactions when hydrocarbons and water are combined.

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