Performing a Titration
Specification Point 3.18:
Describe how to carry out an acid-alkali titration, using a burette, pipette and a suitable indicator, to prepare a pure, dry salt.
Aim:
- To investigate the preparation of a pure, dry salt by titration
Diagram showing the apparatus needed to prepare a salt by titration
Materials:
- Hydrochloric acid, sodium hydroxide solution, goggles and lab coat
- Suitable indicator (methyl orange or phenolphthalein), teat pipette
- Conical flask, burette, stand, volumetric pipette
Method:
- Use the pipette to measure the alkali into a conical flask and add a few drops of indicator.
- Add the acid into the burette and note the starting volume.
- Add the acid very slowly to the conical flask until the indicator changes colour.
- Note and record the final volume of acid in burette and calculate the volume of acid added.
- Repeat the procedure with the same volume of acid and alkali but without the indicator.
- Heat gently to partially evaporate the water, leaving a saturated solution.
- Leave in a dry place so the remaining water evaporates, allowing crystallisation to occur.
- This may take a few days depending on ambient conditions.
Analysis of results:
- After a few days record the appearance of the NaCl crystals to include a diagram and/or photograph.
- In particular comment on their colour and shape.
Conclusion:
- The titration method is used when the salt product is soluble, hence there is no need to filter any insoluble materials.
- The indicator is used to identity the amount of acid needed for neutralisation and is not used in successive titrations to avoid contamination of the product.
- Evaporation of the water leaves the desired pure salt.
Author: Morgan
Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.