Preparation of Oxides:

By direct heating of an element with oxygen

Many metals and non-metals burn rapidly when heated in oxygen or air, producing their oxides, e.g.,

By reaction of oxygen with compounds at higher temperatures

At higher temperatures, oxygen also reacts with many compounds forming oxides, e.g.,

Sulphides are usually oxidized when heated with oxygen.

• When heated with oxygen, compounds containing carbon and hydrogen are oxidized.

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

• By thermal decomposition of certain compounds like hydroxides, carbonates, and nitrates

• By oxidation of some metals with nitric acid

• By oxidation of some non-metals with nitric acid

C + 4HNO₃ → CO₂ + 4NO₂ + 2H₂O

Problem

Why is it not possible to obtain oxygen directly from water?

Solution

Water as such is a neutral stable molecule. It is difficult to break the covalent O-H bonds easily. Hence, electrical energy through the electrolysis process is applied to separate di-oxygen from water. This process requires a tremendous amount of energy.

At cathode:

[H⁺(aq) + e^- → (1/2) H₂(g)] x 4

At anode:

4OH^- (aq) → O₂ + 2H₂O + 4e^-

Net reaction:

Oxygen can thus be obtained from acidified water only by its electrolysis.

Uses of oxygen:

• All air breathing animals and plants use oxygen present in air by the process of respiration. This is known as aerobic respiration.  Without breathing in of air (and the oxygen it contains), life would cease to exist.
• We all know that oxygen is needed to burn fuels. Atmospheric oxygen is used for the combustion of fuel to generate energy in automobiles, aeroplanes, ships, generators, industrial process etc.
• For welding and cutting of metals

In oxy-acetylene and oxy-hydrogen blow torches, oxygen is used for producing very high temperatures required to melt metals. The temperature of oxy-acetylene blow pipe is around 3000^oC, and that of the oxy-hydrogen is around 2800^oC.

• For the production of iron and steel. Usually, in blast furnaces the oxygen in hot air is used. When hot oxygen is directly used, the extraction of iron and steel is much faster.
• In mines, oxygen is used as a part of explosives for blasting rocks.