Consider sodium acetate, NaCH₃COO. We have seen that this is the salt of a strong base (NaOH) and a weak acid (CH₃COOH). When sodium acetate is dissolved in water it dissociates into ions:

NaCH₃COO(s) ® Na⁺(aq) + CH₃COO^-(aq)

This salt is very soluble so this reaction can be considered as going to completion.

In water there is, however, something else going on all the time, the equilibrium which we describe by K_w:

H₂O(ℓ) H⁺(aq) + OH^-(aq)