Is it possible for the equivalence point of a titration to not be at pH 7?

1 Answer
Mar 4, 2017

Yes, in fact, it most often is not.


Besides the trivial examples of non-acid-base titrations, the equivalence point of an acid-base titration is the point where there is only the salt and water in solution, therefore its #pH# is simply the pH of the salt.

When it's a strong acid - strong base titration such as

#NaOH + HCl rarr NaCl + H_2O#
(Sodium Hydroxide - Hydrochloric acid titration)

The remaining salt is made of an extremely weak acid (#Na^+#) and an extremely weak base (#Cl^-#), neither of which is strong enough to change the pH of water which is #7.00#

However, if we do a strong acid - weak base or strong base - weak acid titration, the remaining salt can change the pH. For example:

#NaOH + CH_3COOH rarr CH_3COONa + H_2O#
(Sodium Hydroxide - Acetic acid titration, used - for example - to analyze vinegar)

The pH of sodium acetate will only be 7 in minute enough quantities.