The chemical compounds consisting of oxygen and any other element of a periodic system are called oxides. Depending on properties, they are classified on the main, amphoteric and acid. The nature of oxides can be defined theoretically and a practical way.
It is required to you
- - periodic system;
- - laboratory glassware;
- - chemical reactants.
Instruction
1. You need to represent well how properties of chemical elements depending on their location in D.I. Mendeleyev's table change. Therefore repeat the periodic law, the electronic structure of atoms (oxidation level of elements depends on it) and other.
2. Without resorting to practical actions, you will be able to establish the nature of oxide, using only a periodic system. It is known that in the periods, in the direction from left to right alkaline properties of oxides are replaced with amphoteric, and then - on acid. For example, in the III period oxide of sodium (Na2O) shows the main properties, compound of aluminum with oxygen (Al2O3) has amphoteric character, and okisl chlorine (ClO2) – acid.
3. Keep in mind, in the main subgroups the alkaline properties of oxides amplify from top to down, and the acidity on the contrary weakens. So, in the I group at oxide of caesium (CsO) the basicity is stronger, than at oxide of lithium (LiO). In the V group nitrogen oxide (III) - acid, and oxide of bismuth (Bi2O5) already osnovny.
4. Other way of determination of nature of oxides. The task by practical consideration to prove the main, amphoteric and acid properties of oxide of calcium (CaO), oxide of 5-valent phosphorus (P2O5(V)) and oxide of zinc (ZnO) is Let's say given.
5. At first take two clean test tubes. From bottles, by means of the chemical pallet, fill in one a few CaO, and in other P2O5. Then pour in both reactants on 5-10 ml of the distilled water. Interfere with a glass stick before full dissolution of powder. Lower pieces of litmus paper in both test tubes. Where there is a calcium oxide – the indicator will become blue color that is the proof of the main nature of the studied connection. In a test tube with oxide of phosphorus (V) paper will be painted in red color, therefore, of P2O5 – acid oxide.
6. As oxide of zinc is not soluble in water, for the proof of its amphoteric character carry out reactions with acid and hydroxide. In that and other case the crystals of ZnO will enter chemical reaction. For example: ZnO + 2KOH = K2ZnO2 + H2O3ZnO + 2H3PO4 → Zn3(PO4)2 ↓ + 3H2O