How does salt change the pH of water?

1 Answer
Jun 16, 2016

Answer:

Common salt, #NaCl#, the stuff with which you season your fish and chips, does not change the #pH# of water.

Explanation:

#NaCl# is the salt of a strong acid and a strong base. The salt does not affect equilibrium values of #[H_3O^+]# and #[HO^-]#:

#HCl(aq) + NaOH(aq) rarr NaCl(s) + H_2O#

The reaction as written lies strongly to the right.

On the other hand we could perform the equivalent reaction with the weak acid, hydrogen fluoride:

#HF(aq) + NaOH(aq) rightleftharpoons H_2O(l) + NaF(aq)#

The sodium fluoride product would participate in the back reaction to some extent, and a solution of #NaF# in water would give a slightly basic solution: