5. Sulphides. All sulphides are insoluble save those of ammonium, sodium, and potassium. The sulphides of calcium, barium, strontium, and magnesium are insoluble in water, but are changed by hydrolysis into acid sulphides which are soluble. On this account they cannot be prepared by precipitation.
6. Carbonates, phosphates, and silicates. All normal carbonates, phosphates, and silicates are insoluble save those of ammonium, sodium and potassium.
EXERCISES
1. Write equations representing four different ways for preparing Cu(NO3)2.
2. Write equations representing six different ways for preparing ZnSO4.
3. Write equations for two reactions to illustrate each of the three ways in which reactions in solutions may become complete.
4. Give one or more methods for preparing each of the following compounds: CaCl2, PbCl2, BaSO4, CaCO3, (NH4)2S, Ag2S, PbO, Cu(OH)2 (for solubilities, see last paragraph of chapter). State in each case the general principle involved in the method of preparation chosen.