1. The problem statement, all variables and given/known data Need a little help on a lab. I have all the data for a titration of a weak acid with NaOH which includes the pH of the acid for however many mL of NaOH added. I've plotted a pH vs V NaOH added graph. From that, I plotted a ∆pH/∆V vs V NaOH added graph. From this, I found my equivalence point but the lab is asking me to find Ka for the unknown acid at 0%, 20%, 60% etc titration points where 100% is the equivalence point. From this, I have to identify the acid (it's either acetic acid, monochloroacetic acid, dichloro acetic acid etc. I've found my equivalence point BUT I don't know how to find the Ka for the unknown acid from this equivalence point. 2. Relevant equations Ka = [H+][A-]/[HA] 3. The attempt at a solution [NaOH] is given as 0.099 M (NaOH) I'm guessing [HA] = CBVB/VA Also I'm guessing that [H+] = 10^(-pH) where pH is the ORIGINAL pH of the mixture? I'm unsure on what [OH-] would be.