A buffer calculator

You will write functions for the pH of an acidic buffer, before and after a little strong acid is added, and pick out the buffers that work best.

The idea. $\text{pH} = \text{p}K_a + \log\dfrac{[\text{salt}]}{[\text{acid}]}$. In one solution you can use millimoles instead of concentrations. Added strong acid turns that many millimoles of salt into acid.

Your tasks.

1. Complete buffer_ph(pka, salt, acid) so that it returns the pH.
2. Complete after_acid(pka, salt, acid, added): added millimoles of HCl go in; return the new pH.
3. Set good to the list of names whose pH is within one unit of their $\text{p}K_a$, in the order of the dictionary.