Question

A buffer is prepared by mixing `1*mol` of acetic acid with `1*mol` of sodium acetate...what is the concentration of the buffer?

Answer 1

The molarity is `1.0` `mol*L^(-1)` with respect to both acetic acid, and to sodium acetate. On the other hand, if you have mixed equal volumes of acetic acid and sodium acetate, then the concentration is `0.5` `mol^(-1)`

Explanation:

As you know, this is a buffer solution, whose `pH` would remain very close to the `pK_a` of acetic acid (which is from memory `4.76`).

`pH = pK_a + log_(10){[[OAc^-]]/[[HOAc]]}`.

`HOAc` `=` `H_3C-C(=O)OH`

As I said before, if you have taken equal volumes of `1.0` `mol*L^(-1)` acetic acid and sodium acetate, because you ADDED these volumes, (i.e doubled the volume), the concentration of each reagent is HALVED.