Is Fe2O3 amphoteric Why or why not

Protocol for the practical course in general chemistry - digestion of sparingly soluble oxides and detection of titanium and aluminum

1. Theoretical foundations

Oxygen has the ability to bind (valence) two and is extremely reactive. It forms connections with practically all elements. The most common natural occurrence of many elements occurs in the form of their oxides. Metals generally form ionic oxides, while non-metals form covalent oxides. (1)

As a result of their low ionization energy, metals react with oxygen to form ionic solids in which oxygen is present as an oxide ion. Since the oxide ion is relatively small and highly charged, metal oxides have high lattice energies. As a result, the melting points of these ionic oxides are very high (around 2000 ° C) and most of them are poorly soluble in water. (2) For example, Al2O3 is the abrasive known as corundum and SiO2 is quartz. (1)

Metal oxides are even in conc. HCl or poorly soluble in aqua regia. These substances have to be digested separately. The type of digestion depends on the individual substances, a distinction being made between acidic and basic digestion. With a melt of soda-potash, alkaline earth sulfates, highly annealed oxides, silicates and silver halides are broken down. With the help of the acidic digestion, apart from TiO2, Fe2O3, BeO, MgO, Ga2O3 and Cr2O3 can also be digested (3)

1.1) The acidic digestion with KHSO4:

As already mentioned, in addition to TiO2, Fe2O3, BeO, MgO, Ga2O3 and Cr2O3 can also be digested in acid digestion. In this case, TiO2 is digested. Titanium (IV) oxide (TiO2) is a white, insoluble pigment that has both basic and acidic properties.

According to the periodic table of the elements, Ti (together with Zr and Hf) has a d2s2 electron configuration. Ti and Zr show the oxidation states + II, + III and + IV. This is an example of a general course in transition metals: The low oxidation numbers lose importance in the second and third transition metal series because the valence electrons are further away from the core. If the atoms then give up some electrons, it is quite likely that they will immediately lose all valence electrons. The lower oxidation states of Ti are ionic, while the oxidation number + IV corresponds to a more covalent and non-metallic behavior. (1)

Ti (II) oxide, TiO, is basic and ionic and has the NaCl crystal structure.

Reaction equation for acidic digestion:

First, formation of potassium disulphate through the removal of water in the case of potassium hydrogen sulphate

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Extraction of the more easily soluble sulfates from the poorly soluble oxides

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Detection of titanyl ions:

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1.2) The alkaline digestion with Na2CO3 and K2CO3 / soda-potash digestion

Some water-insoluble oxides are soluble in acids and bases. These oxides are known as amphoteric. As can be seen from the figure below, most of the elements that form amphoteric oxides lie on the diagonal that separates metals and non-metals in the periodic table. (2)