You will need
- – periodic system;
- – laboratory utensils;
- – chemical reagents.
You need to know well how the properties of chemical elements change depending on their location in the table D.I. Mendeleev. So repeat the periodic law, the electronic structure of atoms (the degree of oxidation of elements depends on it) and other.
Without resorting to practical action, you will be able to establish the nature of the oxide using only the periodic system. After all, it is known that in periods, in the direction left to right alkaline properties of oxides are changed to amphoteric, and then – to acidic ones. For example, in period III, sodium oxide (Na2O) exhibits basic properties, the compound of aluminium with oxygen (Al2O3) is amphoteric, and chlorine oxidation (CLO2) is acidic.
Keep in mind, in the main subgroups, the alkaline properties of oxides are enhanced from top to bottom, and the acidity vice versa weakens. Thus, in group I, caesium oxide (CSO) is stronger than that of lithium oxide (LiO). In Group V, nitric (III) oxide is acidic and bismuth oxide (Bi2O5) is already basic.
Another way of determining the nature of oxides. Let’s say, it is given a problem to prove the main, amphoteric and acid properties of calcium oxide (CaO), 5-valence phosphorus oxide (P2O5 (V)) and zinc oxide (ZnO).
First take two clean test tubes. From the sclings, with the help of a chemical spatula, pour into one bit of CaO, and into the other P2O5. Then pour 5-10ml of distilled water into both jets. Stir with a glass stick until the powder is completely dissolved. Lower pieces of litmus paper into both test tubes. Where calcium oxide is located — the indicator will become blue, which is proof of the main nature of the compound under study. In a test tube with phosphorus (V) oxide, the paper will color red, hence P2O5 is an acid oxide.
Since zinc oxide is not soluble in water, to prove its amphoterness, conduct reactions with acid and hydroxide. In both cases, ZnO crystals will enter into a chemical reaction. For example:
ZnO + 2KOH = K2ZNO2 + H2O
3ZNO + 2H3PO4→ Zn3 (PO4) 26:+ 3H2O