# Science

posted by
**Sunshine** on
.

Given:

Concentration of acetic acid 0.1M and 30mL used.

Concentration of hydrocholoric acid 0.1M and 15mL used.

Concentration of sodium hydroxide 0.1M and 5mL used.

I need to calculate the pH before any NaOH is added and after the NaOH is added.

I think i am suppose to use the Henderson-Hasselbach equation but i don't know how.

The equation is pH= pKa + log[conjugate base]/[acid]

I understand that [conjugate base]/[acid] will be a 2/1 ratio so the log of that is 0.30. But i don't know how to get the pKa?