Acid Base Titrations

Titrations and Titration Curves

What reaction occurs when a base / alkali is added to an acid?

Neutralisation reaction- forms a salt and water.

What happens to pH when a base / alkali is added to an acid?

pH increases.

What is a titration curve?

Titration curves shows the pH against the volume of base added from titration.

• Titration curves show the different combinations of weak and strong acids and bases.

What are the different combinations of weak / strong acids and bases?

1. Strong acid / strong base

2. Strong acid / weak base

3. Weak acid/ strong base

4. Weak acid / weak base

Titration curve for a strong acid / strong base reaction.

Titration curve for a strong acid / weak base reaction.

Titration curve for weak acid / strong base reaction.

What is the equivalence point?

This is the point where the acid has been fully neutralised by the base.

• The pH of this solution is the mid-point of the vertical part of the titration curve e.g. for strong acid / strong base reaction the pH is 7 (neutral).

What is the half neutralisation point?

This is the point halfway between 0 and the equivalence point.

What is the significance of the half neutralisation point?

• When an acid is half-neutralised, the concentration of the acid is equal to the concentration of the salt.

[HA] = [A-]

• K_a= [H⁺]

taking -log on both sides

• -logK_a= -log[H⁺] i.e. pK_a = pH