[johnj7]

Hello,
I'm struggling with the concept of "salting-out" and I the solubility of certain substances.
I know that adding NaCL to water will cause the polarity to increase by a lot, but what will adding NaOH to water do to the polarity?  Will it also increase?

The question I'm really trying to figure out is this: the solubility of benzoic acid in water is 3.4 g/l.  The solubility of benzoic acid in 0.1M solution of NaOH is 12.2 g/L. Explain why this is so much larger than the solubility in water. 

Here's my attempted answer:  water has only hydrogen bonds to offer to try to break up the association of benzoic acid molecules.  Since hydrogen bonds are relatively weak, the benzoic acid molecules would rather associate with each other than with water.  Consequently, the solubility of benzoic acid is small.  Benzoic acid is also largely non polar, and will not like to associate with water.  In a solution of NaOH, there will be stronger ion-dipole reactions (?) and thus more benzoic acid dissolves.  Does more benzoic acid also dissolve because NaOH decreases polarity?

Any help/clarity is much appreciated.

[Arkcon]

NaOH does something else, quite fundemental, that helps benzoic acid dissolve.

[johnj7]

Oh okay, so NaOH strips the hydrogen off benzoic acid, meaning that there will be no more hydrogen bonding between benzoic acid molecules, and that's why it dissolves? 

[agrobert]

Does salt dissolve in water?  What kind of bond is held between NaCl? How is sodium benzoate similar?

[johnj7]

hmm okay, I think I got it
So NaOh strips the hydrogen off of benzoic acid, creating an anion which forms a salt with Na.  Salts like NaCl are held together with ionic bonds, which easily separate in water.  Therefore, the solubility of benzoic acid is more soluble in 0.1 M solution of NaOH than in just water. 

Thanks for the help