Benzoic Acid Question

[Darthoper]

Hey guys just joined this forum because of my new love for science

I have just started college and today we was performing a basic experiment involving separation of molecules in a mixture. This mixture had NaCl Benzoic Acid and Sand. In one step we turned the acid from a solid to a liquid by adding a base (which I have no idea what it was). Adding the base turned the acid into a liquid which we then filtered to separate from the mixture. Once seperated we added some HCL thus turning it back into a solid. My question is how exactly does adding a base or acid change the makeup of the molecule? Just curious as to how this works

 

-thanks

[mississippichem]

If your already familiar with pH, common monoatomic and polyatomic ions, then do some reading on acid/base equilibrium, as well as solubility product constants. They would be a good place to start in the understanding of acid/base chemistry.

 

What do you already understand? I'll try to post a very general explanation on the forum.

[Horza2002]

Basically, acids and bases are opposite. Look up the structure of carboxylic acid...the proton (H) of the group is removed in the presence of a base.

 

Upon addition of a base, the acid does not become a "liquid" it dissolved in the solvent (which im guessing was water). Deprotonated carboxylic acids are very soluble in water. Then you passed it through the filter paper which would have removed the sand. HCl is hydrochloric acid, so is the opposite of the base you added at the start. This puts the H back on the carboxylic acid and turns the acid back to a solid.