| MadSci Network: Chemistry |
|
what is the difference between strong acid and concentrated acid?
A strong acid is one that is completely dissociated in a particular solvent, when the concentration is not too high: HA + S ® A- + HS+ How strong this needs to be will vary from solvent to solvent, but we normally think of a strong acid as one that is completely dissociated in water.We need to be careful here: phosphoric acid (H3PO4) is a strong acid, but does not lose all three protons in aqueous solution. H3PO4 + 2H2O ® HPO4-- + 2H3O+ H3PO4 normally behaves in water as a dibasic (2-proton) acid toward weak bases. It takes a pretty strong base, like hydroxide, to remove the third proton.A weak acid is one that is only partly dissociated, no matter what the concentration. For example, acetic acid (the active ingredient in vinegar) is only about 1% dissociated in water, even in dilute solutions. A concentrated acid is an acid which is either pure (no solvent) or has a high concentration. Glacial acetic acid is a concentrated weak acid, and industrial sulfuric acid (about 98% by weight, the other 2% is water) is a concentrated strong acid. Even strong acids are not completely dissociated when the concentration is too high: concentrated hydrochloric acid, even though it is only 12-13 moles per liter in water, is concentrated enough that there are irritating fumes of HCl gas above the acid. If you dilute the acid to 6 moles per liter, the fumes are no longer noticeable because the HCl is completely dissociated.
|
Try the links in the MadSci Library for more information on Chemistry.