how can you work out the pKa from a titration curve graph?

Question

i can't work out the pKa, and not sure where to draw the line.
can you please help me?

Answer 1

The determination of the Ka, of a weak acid can be difficult. However, its pKa can be easily estimated by analysis of its titration curve. The pK,, is the pH value at the half equivalence point, that is, the point at which only half of the volume of alkali needed to reach the equivalence point has been added.

Answer 2

Finding Pka From Titration Curve

Answer 3

The first answerer is correct, the pKa is the pH at half the equivalence point. I've explained how you find this point below, bear with me it is difficult to describe without a diagram:

The equivalence point is the end point of the acid base titration (not always pH 7) . So on your titration curve you will see a steep rise then a shallow gradient and then another steep rise. The shallow gradient is caused by the reaction of the acid with the base, you add one to the other but the pH doesn't change because the OH- ions being added are being used up to react with the H+ ions in your acidic solution (or vice versa). So the change in pH is gradual, (this is also how buffers work)

When the gradient suddenly becomes steep again this is where all the acid has reacted with base and so the addition of the further OH- ions leads to a sharp increase in pH.. This is the equivalence point. Half the equivalence point is then the point at which half the volume of acid (or alkali) has been added

Answer 4

This Site Might Help You.

RE:
how can you work out the pKa from a titration curve graph?
i can't work out the pKa, and not sure where to draw the line.
can you please help me?

Answer 5

Titration Diagram

Answer 6

10pointspka buffer titrations graph