CLASSIFICATION OF OXIDES

Metals and non-metals can react with oxygen to produce compounds called oxides. Therefore,an oxide can be defined as a chemical compound in which one or more oxygen atoms are combined with another element. There are four main classes of oxides: Acidic oxides, Basic oxides, Amphoteric oxides, and Neutral Oxides.

ACIDIC OXIDES\

Acidic oxides are formed when certain non-metal atoms react with oxygen, and so, form acidic solutions when dissolved in an aqueous solution. As such, these compounds (when dissolved in an aqueous solution) can react with alkalis to form salt and water.

SO3(g) + H2O(l) -> H2SO4(aq)

2KOH(aq) + CO2(g) -> K2CO3(aq) + H2O(l)

BASIC OXIDES

Basic oxides are formed when a metal reacts with oxygen. However, only some of these compounds will form alkaline solutions when reacted with water (as most basic oxides are insoluble).These metals are called alkalis, and can react with acids to form a salt and water.

2Cu(s) + O2(g) -> 2CuO(s)

2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g)

NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(l)

AMPHOTERIC OXIDES

Amphoteric oxides refer to metal oxides which can exhibit both acidic and basic properties. Upon reacting with an acid, these compounds neutralize the acid to form a salt and water. Similarly, upon reacting with an alkali, these compounds neutralize the alkali to form a salt and water. The three amphoteric oxides required are: Aluminum Oxide (Al2O3), Lead (II) Oxide (PbO), and Zinc Oxide (ZnO).

ZnO(aq) + 2HCl(aq) -> ZnCl2(aq) + H2O(l)

ZnO(aq) + 2KOH(aq) -> K2ZnO2(aq) + H2O(l)

NEUTRAL OXIDES

Neutral oxides refer to oxides that exhibit neither acidic nor basic properties (usually non-metal oxides). Eg: Carbon monoxide (CO), Nitrogen monoxide (NO).