Chemical compounds consisting of oxygen and any other element of the periodic system, called oxides. Depending on the properties, they are classified into basic, acid and amphoteric.
The character of the oxides can be determined theoretically and practical way.
You will need
- - Periodic systematic
- - glassware-
- - chemical reagents.
You need a good understanding of howproperties of chemical elements vary depending on their location in the table D. Mendeleev. So 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 action, you canestablish the nature of the oxide, using only the periodic system. It is known that in the period from left to right alkaline properties of oxides are replaced on amphoteric, and then - to the acid. For example, exhibits basic properties of aluminum with oxygen compound (Al2O3) has an amphoteric character and oxidized chlorine (ClO2) in the period III sodium oxide (Na2O) - acid.
Keep in mind, in the main subgroups of alkalineproperties oxides amplified downward, and vice versa acidity is weakened. So, in I group, cesium oxide (CsO) basicity stronger than that of lithium oxide (LiO). In group V nitric oxide (III) - acid and bismuth oxide (Bi2O5) have basic.
Another way to determine the nature of oxides. Assume given task empirically prove basic, acid and amphoteric properties of calcium oxide (CaO), oxide 5-valent phosphorus (P2O5 (V)) and zinc oxide (ZnO).
First take two clean test tubes. From flasks by trowel chemical, pour into one bit of CaO, and in another P2O5. Then pour into both reagent 5-10 ml distilled water. Glass rod stir to completely dissolve the powder. Dip the pieces of litmus paper in both tubes. Where is calcium oxide - an indicator turns blue, which is a proof of the fundamental nature of the test compound. In a test tube with phosphorus oxide (V) paper turn red, therefore, P2O5 - acidic oxide.
Since zinc oxide is not soluble in water, to prove his swipe amphoteric reaction with the 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