Preparation of salts

There are 3 ways to prepare salt in the lab, and I will show you how to remember which are the techniques to use for the different salts.

1. Precipitation - this is only for preparation of insoluble salts e.g. lead (II) chloride, barium sulfate & lead (II) carbonate.

2. Titration - this is for the preparation of soluble salts, such as sodium, potassium & ammonium.

3. Acid + excess insoluble substance - usually for other soluble salts, less the ones listed in method 2.

I will go into details how this is done during my tuition classes.

Why is copper (II) sulfate sometimes 'blue' and other times 'white' in colour?

The copper (II) sulfate crystals that you see in the lab are obviously blue in colour. The same goes for the copper (II) sulfate solution. This is because copper (II) sulfate is hydrated, meaning to say it has water of crystallisation attached to the salt.

CuSO4.5H2O -----------------------> CuSO4 + 5H2O



Once you heat the copper (II) sulfate crystals, they will lose the water of crystallisation, thus forming white powder. Copper (II) sulfate is said to be 'anhydrous', meaning 'dry'.

Anhydrous copper (II) sulfate powder is also used to test for the presence of water.