Why is the equivalence point so steep?

Question

Hi!

As the title suggests, I would like to know why the equivalence point in a titration curve is so steep? I know that the titration curve is logarithmic, because pH is logarithmic, but why will it suddenly become so steep just at the equivalence point?

Answer 1

The reason it is so steep right at the equivalence point is because at that point there is NO MORE analyte present, and everything in the flask is now the titrant. For example, when titrating HCl with NaOH (which I know is what you're doing), up to the equivalence point there is HCl, and the amount of HCl becomes less and less as you add NaOH. Right at the equivalence point, the moles of HCl and moles of NaOH are equal, so the very next drop of NaOH causes the pH to shoot up rapidly because the pH goes from neutral to > 7. Right?