Chemical compounds consisting of oxygen and any other element of the periodic system are called oxides. Depending on the properties, they are classified into basic, amphoteric and acidic.
The nature of the oxides can be determined theoretically and practically.
You will need
- - periodic system-
- - glassware-
- - chemical reagents.
You need to be well aware of howThe properties of chemical elements vary depending on their location in the DI table. Mendeleev University. Therefore, repeat the periodic law, the electronic structure of atoms (the degree of oxidation of the elements depends on it), and so on.
Without resorting to practical actions, you will be able toEstablish the nature of the oxide using only a periodic system. After all, it is known that in the periods, from left to right, the alkaline properties of the oxides are replaced by amphoteric, and then - acidic. For example, in the III period, sodium oxide (Na2O) exhibits basic properties, the aluminum-oxygen compound (Al2O3) is amphoteric in nature, and the chlorine (ClO2) oxide is acidic.
Keep in mind, in the main subgroups of alkalineThe properties of oxides are amplified from the top down, and the acidity on the contrary weakens. Thus, in group I cesium oxide (CsO) has more basicity than lithium oxide (LiO). In group V, nitric oxide (III) is acidic, and bismuth oxide (Bi2O5) is the main one.
Another way to determine the nature of oxides. Let us assume that the task is given by an experimental test to prove the basic, amphoteric and acidic properties of calcium oxide (CaO), 5-valent phosphorus oxide (P2O5 (V)) and zinc oxide (ZnO).
First, take two clean test tubes. From the bottles, with a chemical spatula, fill in a little CaO, and in another P2O5. Then pour 5-10 ml of distilled water into both reagents. Stir the glass rod until the powder is completely dissolved. Lower the pieces of litmus paper into both test tubes. Where there is calcium oxide - the indicator will turn blue, which is a proof of the main character of the test compound. In a test tube with phosphorus oxide (V), the paper will turn red, hence P2O5 is an acid oxide.
Since zinc oxide is insoluble in water, to prove its amphotericity, react with acid and hydroxide. In either case, the ZnO crystals enter into a chemical reaction. For example:
ZnO + 2KOH = K2ZnO2 + H2O
3ZnO + 2H3PO4? Zn3 (PO4) 2? + 3H2O