Prepare a Salt by Titration
- If salts are prepared from an acid and a soluble reactant then a titration technique must be used
- In a titration, the exact volume of acid and soluble reactant are mixed in the correct proportions so that all that remains is the salt and water
Preparing a Salt by Titration
Aim:
To prepare a sample of a dry salt starting from an acid and an alkaliDiagram:
Diagram showing the apparatus needed to prepare a salt by titration
Method:
- Use a pipette to measure the alkali into a conical flask and add a few drops of indicator (phenolphthalein or methyl orange)
- Add the acid into the burette and note the starting volume
- Add the acid very slowly from the burette to the conical flask until the indicator changes to appropriate colour
- Note and record the final volume of acid in burette and calculate the volume of acid added (starting volume of acid - final volume of acid)
- Add this same volume of acid into the same volume of alkali without the indicator
- Heat to partially evaporate, leaving a saturated solution
- Leave to crystallise decant excess solution and allow crystals to dry
Results:
A dry sample of a salt is obtainedExam Tip
When evaporating the solution some water is left behind to allow for water of crystallisation in some salts and also to prevent the salt from overheating and decomposing.
