Specification Point 2.40C (Paper 2C Only):
Describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an Acid and Alkali
Preparation of Soluble Salts
Using Dilute Acid and Alkali:
The heating of the mixture to leave a saturated solution
- Use pipette to measure alkali into conical flask and add a few drops of indicator (phenolphthalein or methyl orange)
- Add acid into burette and note the starting volume
- Add acid in burette into alkali in flask until 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 to leave a saturated solution
- Leave to crystallise
- Excess solution is decanted and crystals are blot dry
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