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Titration and pH Calculations

Afternoon.
I'm having a bit of trouble with some of my pH titration calculations.

I titrated 50 ml of 0.1 mol dm-3 histidine monohydrochloride (H2A+ Cl-) with a solution of 0.5 mol dm-3 of NaOH and measured the pH after adding every 1 ml. I have the expected graph, showing the two end points etc and everything seems to have worked. However I need to work out the estimated end points for 100% HA and 100% A- from the concentrations of histidine and NaOH (where the formation of HA from H2A+ is the first end point and the formation of A- from HA is the second end point)

How would I go about doing this?

I think it's something stupidly obvious, but can't work out what it is. And I hope the question makes sense.

Thanks for any advice you can give!

P.S. if you think I've missed a vital bit of information needed, tell me.