Respuesta :

When a mixture consists of a weak acid, such as HF, and its corresponding salt, NaF, this is an acid buffer. So, we can use the equation as written below:

pH = pKa + log(salt/acid)

For HF, the pKa = 3.17

Thus,
pH = 3.17 + log(0.12/0.26)
pH = 2.83