2.4: Titration Curves

Titration

An experiment where measured amounts of base are added to a measured amount of acid while monitoring the pH

What is the equivalence point?

The point where the acid has been exactly neutralized by the added base

What happens to a weak acid as base is added?

The weak acid is progressively converted into its conjugate base.

What is the inflection point on a titration curve?

The point where the pH equals the pKa of the weak acid

What happens at the inflection point?

The weak acid and its conjugate base are present in equal concentrations

How much base is added at the inflection point for a monoprotic acid?

0.5 mol of base for every 1 mol of acid

What is the pKa of acetic acid?

4.76

What is the pH at the inflection point when titrating acetic acid?

4.76

What is the composition at the inflection point?

50% acetic acid and 50% acetic ion

What happens to pH near the pKa during titration?

The pH changes very little as more base is added

What happens at the equivalence point when titrating acetic acid?

1 mol of base has been added for every 1 mol of acid, and essentially all the acetic acid has been converted to acetic ion

What determines the pH values at the inflection and equivalence points?

The pKa of the individual acid

What is a monoprotic acid?

An acid that can release one H+ and has one Ka and one pKa

What is a diprotic acid?

An acid that can release two H+ and has tro Ka values and two pKa values

What is a polyprotic acid?

An acid that can release more than two H+ and has multiple Ka nd pKa values

What are examples of polyprotic acids?

Citric acid and phosphoric acid

What happens when pH < pKa?

The protonated form of the acid predominates (H+ stays on)

What happens when pH > pKa?

the deprotonated form/conjugate base predominates (H+ comes off)

At what point are [HA] and [A-] equal?

When pH = pKa

During titration, what happens to HA and A-?

As more base is added, HA decreases while A- increases