Required Practical: Strong Acid & Strong Alkali Titration (AQA GCSE Chemistry)

Objective:

To determine the reacting volumes of a strong acid and a strong alkali by titration

Hypothesis:

The titration method can be used to calculate the concentration of an acid

Materials:

• 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
• Phenolphthalein indicator
• Clamp stand, clamp & white tile

Performing a titration

Method:

1. Use the pipette and pipette filler and place exactly 25 cm³ sodium hydroxide solution into the conical flask
2. Place the conical flask on a white tile so the tip of the burette is inside the flask
3. Add a few drops of a suitable indicator to the solution in the conical flask
4. Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm³ portions, while swirling the flask vigorously
5. Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus
6. Now repeat the titration with a fresh batch of sodium hydroxide
7. 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
8. Record the volume to the nearest 0.05cm³
9. Repeat until you achieve two concordant results (two results that are within 0.1cm³ of each other) to increase accuracy

Results: 

Record your results in a suitable table, e.g:

Evaluation:

Only concordant results should be used to calculate a mean titre

Conclusion:

The mean titre is calculated and used to calculate the concentration of the acid in mol/dm³, ignoring any anomalous results