Titration Curve. Specifically, acid-base properties of amino acids?

Question

y-axis is pH, x-axis is "Molar Equivalents." How do I get that value? I have the volume of 1 N of HCl and 1 N NaOH and the pH value of every 0.1 mL of HCl/NaOH that added to the unknown amino acid.

Answer 1

On thee x-axis you need to put the equivalents you added:

gr-eq or molar equivalents= valency*N*V
for both HCl and NaOH valency=1

so you will have 1*1*V where V is the volume you added (in liters).

E.g. imagine you started from a pH=2 (nothing added to the solution).
Then the first point has co-ordinates (x,y)= (0,2)
If you added 0.1ml of NaOH and the pH became pH=2.2 then your next point has x=1*1*0.1*10^-3 = 0.1*10^-3 gr-eq or for simiplicty 0.1 mgr-eq (so that you don't have always the 10^-3 in your way) so your second point would be (0.1, 2.2)

Imagine you add another 0.1 ml of NaOH and the pH becomes pH=2.4. The total volume that you will have added is 0.2 (remember you already added 0.1ml in the first step), so your third point will be (0.2, 2.4) and so on...

Similarly you do for addition of HCl

Answer 2

Extrapolate.