AQA GCSE Chemistry

Revision Notes

4.2.9 Required Practical: Strong Acid & Strong Alkali Titration

Required Practical 2: Strong Acid & Strong Alkali Titration

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

Titration, downloadable IB Chemistry revision notesTitration apparatus, downloadable AS & A Level Chemistry revision notes

Performing a titration

Practical Tip:
Make sure you remove the funnel after filling the burette as if left it can drop solution into the burette, leading to error

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:

Titration Results Table

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

Exam Tip

Use a funnel to fill the burette but be sure to remove it before starting the practical as it can drip liquid into the burette, making the initial reading false.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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