Hello,

I recently did an experiment in chemistry where we performed a titration of an unknown weak monoprotic acid with NaOH. We took an aliquot of 25ml of this (stock) acid and diluted it with 225mL of distilled water so that the volume becomes 250mL. We then poured 25mL of this diluted acid into a plastic cup to use in our titration, and then added another 100mL of distilled water. We also measured the pH at every point in the titration. One of our jobs is to calculate the concentration of this diluted acid solution, and I was wondering how we would do that (when I say the concentration of the diluted acid solution, I mean the concentration of the diluted acid BEFORE the 100mL of distilled water was added into the plastic cup to use for in the titration)? The initial pH of the solution (when the total volume of NaOH added from the buret to the solution is 0) was 2.72, so I was thinking you do 10^-2.72 to get the initial concentration. Please let me know if I am wrong, and if so, how I can determine this.

The volume of NaOH added and the pH at the equivalence point is 15.19mL and 8.172 respectively, and the volume of NaOH added and the pH at the half-equivalence point is 7.595mL and 3.60 respectively.

Thank you very much.