Preparing Soluble Salts Using Titration

Preparing Soluble Salts Using Titration

The exact amount of acid needed to neutralise an alkali can be found by titration. This technique can be used to make pure crystals of a soluble salt (one that dissolves in water).

In the example below, an acid and an alkali react to make sodium chloride.

1. Theburette is filled with hydrochloric acid.

2. A known quantity ofalkali (say 50 cm³ sodium hydroxide) is released from a pipette into the conical flask. The tap on the burette is turned open to allow the acid to be added drop by drop into the

3. Thealkali contains an indicator (phenolphthalein).

4. When enoughacid has been added to neutralise the alkali, the indicator changes from pink to colourless. This is the end point of the

5. Thetitration can be repeated using the same amounts of acid and alkali but without the

6. Puresalt crystals which are free from indicator can then be crystallised from the neutral