Acid-Alkali Titrations (Edexcel IGCSE Chemistry (Modular))
Revision Note
What is a 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
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
Results
Results table for a titration
Rough titre (cm3) | Titre 1 (cm3) | Titre 2 (cm3) | Mean (cm3) |
---|---|---|---|
15.50 | 14.90 | 15.00 | 14.95 |
Examiner 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.
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