How to calculate pH of a solution containing salt of a weak acid

A salt of a weak acid (e.g. sodium acetate, NaAc) is composed of the conjugate base of the acid (acetate, Ac^- ) and a counter ion (sodium). The conjugate base is negatively charged and the counter ion is positively charged. When the salt dissolves in solution it completely ionizes into the two components. Thus, if a salt such as NaAc is dissolved in solution to make 0.001 M concentration then the concentration of acetate  (Ac^-) is 0.001 M and of (Na⁺) is 0.001 M. Acetate ions act as a weak base (can accept a proton from water) as shown in the following chemical equations:

                                                             Ac^-  + H₂O à HAc + OH^-

In order to calculate pH of a salt solution such as sodium acetate we need to find Kb value for acetate (Ac^-) which can be calculated from Ka value of the acid (HAc) (see the post that describes how to make this calculation). The equation used for calculation of pH for a weak base in solution can then be applied. For the above example C = 0.001 M and Kb = 5.68 × 10^-10 pH = 7.88. Online pH calculator can be used given that the salt acts as a weak base.