Calculating the pH of a weak acid and its salt [ENDORSED]

[Raya Amin 2A]

Hi!

On the outline it says that we should be able to calculate the pH of a weak acid and its salt, and a weak base and its salt (which is how buffers are made). I know we covered how to calculate the pH of salt solutions in class, but I was wondering if we are going to be expected to know how to calculate the pH for buffer solutions? If so, how would we calculate the pH for one of these problems?

[Chem_Mod]

Here is an example I made to calculate the pH of a weak acid and its salt.
Click the image to enlarge:

This approach uses the concepts and problem solving covered in Chem 14B (Weeks 1 and 2).

We are not making buffers in Chem 14B but the following is how one makes them in lab courses.

Acidic buffers are made using a weak acid and adding its conjugate base as a salt so that the concentrations of weak acid (HA) and its conjugate base (A^-) are approximately equal.

Basic buffers are made using a weak base and adding its conjugate acid as a salt so that the concentrations of weak base (B) and its conjugate acid (HB⁺) are approximately equal.

Having both the acid and base in approximately equal concentrations results in both being present to act as a buffer (neutralize an added base, or neutralize an added acid).