Acid-Base Titrations

Titrations are a method of analysing the concentration of solutions
They can determine exactly how much alkali is needed to neutralise a quantity of acid – and vice versa
You may be asked to calculate the moles present in a given amount, the concentration or volume required to neutralise an acid or a base
Titrations can also be used to prepare salts

The typical materials needed are:
- 25 cm³ volumetric pipette
- Pipette filler
- 50 cm³ burette
- 250 cm³ conical flask
- Small funnel
- 0.1 mol/dm³ sodium hydroxide solution
- Sulfuric acid – concentration unknown
- A suitable indicator
- Clamp stand, clamp & white tile

The steps in performing a titration

Describing the method:

Use the pipette and pipette filler and place exactly 25 cm³ sodium hydroxide solution into the conical flask
Place the conical flask on a white tile so the tip of the burette is inside the flask
Add a few drops of a suitable indicator to the solution in the conical flask
Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm³ portions, while swirling the flask vigorously
Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus
Now repeat the titration with a fresh batch of sodium hydroxide
As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour
Record the volume to the nearest 0.05 cm³
Repeat until you achieve two concordant results (two results that are within 0.1 cm³ of each other) to increase accuracy

Indicators are used to show the endpoint in a titration
Wide range indicators such as litmus are not suitable for titration as they do not give a sharp enough colour change at the endpoint
However, methyl orange and phenolphthalein are very suitable
Some of the most common indicators with their corresponding colours are shown below:

Acid-Base Titrations (Cambridge O Level Chemistry)