Heres a question involving what I'm talking about When 5mls of 0.05M CH3COOH is allowed to react with 1.5mls of 0.05M KOH. The pH is found to be 4.43. Using the Henderson-Hasselback equation calculate the pKa. My teacher told me that you can find the amount of dissociated ions of the weak acid without even knowing the dissociation constant by writing out the reaction equation for the reaction with the base and if its a 1:1 reaction for example the amount of dissociated ions will be equal to the amount of the base that was added. Why is this? Why would the amount of dissociated acid ions be equal to the amount of base I add?