Core Practical: Acid-Alkali Titration (Edexcel GCSE Chemistry)

Core Practical: Acid-Alkali Titration

• Titrations are a method of analysing the concentration of solutions

• Acid-base titrations are one of the most important kinds of titrations

• 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

How to carry out a titration

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 0.05 cm³

9. Repeat until you achieve two concordant results (two results that are within 0.1 cm³ of each other) to increase accuracy

Results:

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

Hazards, risks and precautions

Hazard symbol to show substances that are harmful to health

• Dilute hydrochloric acid is not classified as hazardous at the concentrations typically used in this practical, however it may still cause harm to the eyes or the skin

• Sodium hydroxide may be considered to be harmful to health, depending on the concentration used as it is irritating to the eyes and skin

• For both sodium hydroxide and hydrochloric acid, avoid contact with the skin and use safety goggles