The titration curve should have flat regions centered around each of the
three halfway points (buffer zones) and sharp increases in pH around the
equivalence points.
Initial pH
This is determined by the most acidic of the Ka values and the initial
concentration of the acid. (Same as a monoprotic acid)
Half-way points
At each halfway point, the pH = pKa of the group you are titrating. At this point in
the titration curve, we are in a buffering region, and the curve will be relatively
flat.
Equivalence points
At each equivalence point, the pH is the average of the pKa values above and
below. At the last equivalence point (the endpoint), the pH is determined by the
Kb of the conjugate base of the weakest acid.
Plotting the titration of 100 mL of 0.10 M phosphoric acid with 1.0 M NaOH.
H3PO4 + H2O H2PO4
-
+ H3O+
Ka1 = 7.5 x 10-3
H2PO4
-
+ H2O HPO4
2- + H3O+
Ka2 = 6.2 x 10-8
HPO4
2- + H2O PO4
3- + H3O+
Ka3 = 4.2 x 10-13
Plot these points and connect them to determine the titration curve of phosphoric acid. The curve should be relatively flat around each of the halfway points when we are in a buffering region.
The titration curve should have flat regions centered around each of the
three halfway points (buffer zones) and sharp increases in pH around the
equivalence points.
For more information on the titration curve click on the link below:
brainly.com/question/3130161
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