Lecture 6 – Preparation of Salts: Precipitation

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 5a	www.bbc.co.uk
Figure 5b	socratic.org

Precipitation:

Precipitation is the method used to prepare insoluble salts. In this method 2 soluble solutions are reacted together to yield an insoluble salt. The insoluble salt is obtained by using filtering the solution and washing the residue insoluble salt with water and drying it, or decanting as shown in Figure 5a and 5b, respectively.

Figure 5a:

Figure 5b:

Example: Barium sulphate is prepared using aqueous solutions of barium chloride and sodium sulphate.

Salts and their solubilities:

Table 5: Salt and their solubilities are shown in the Table below.

Soluble	Insoluble
All nitrates	None
All Chlorides except	Silver chloride; AgCl Lead chloride PbCl2 Mercury chloride HgCl2
All Sulphates except	Cacium sulphate; CaSO4 Barium sulphate; BaSO4 Lead sulpahte; PbSO4
Sodium carbonate; Na2CO3 Potassium carbonate; K2CO3 Calcium carbonate; CaCO3	All Carbonates except