It should also be pointed out that even though we have written acid-base reactions so far as
involving protons, in aqueous solution the protons will interact with other water molecules, forming
H 3 O+, known as the hydronium ion. The water dissociation reaction can therefore be written as
H 2 O(l) + H 2 O(l) H 3 O+ (aq) + OH− (aq)We shall be using H+ and H 3 O+ interchangeably, unless otherwise stated.
STRONG ACIDS AND BASES
Strong acids and bases are those that completely dissociate into their component ions in aqueous
solution. For example, when NaOH is added to water, it dissociates completely:
NaOH (s) + (excess) H 2 O (l)→ Na+ (aq) + OH− (aq)BASIC CONCEPT
Strong acids and bases completely dissociate into their component ions in aqueous solution.Hence, in a 1 M solution of NaOH, complete dissociation gives 1 mole of OH− ions per liter of
solution.
pH = 14 − pOH = 14 − (−log [OH−]) = 14 + log [1] = 14Virtually no undissociated NaOH remains. Note that the [OH−] contributed by the dissociation of H 2 O
is considered to be negligible in this case. The contribution of OH− and H+ ions from the dissociation
of H 2 O can be neglected only if the concentration of the acid or base is much greater than 10−7 M.
Strong acids commonly encountered in the laboratory include HClO 4 (perchloric acid), HNO 3 (nitric
acid), H 2 SO 4 (sulfuric acid), and HCl (hydrochloric acid). Commonly encountered strong bases