Oxidising agent warning

Oxidation and Reduction

Oxidation

Oxidation is the addition of oxygen or the removal of hydrogen. An
oxidising agent is a substance that adds oxygen to or removes hydrogen from another substance. Burning, respiration and rusting are common examples of oxidation.

Some oxidation reactions
ReactionExplanation
S(s) + O2(g) → SO2(g)Sulphur is oxidised to sulphur dioxide by the addition of oxygen
H2S(g) + Cl2(g) → 2HCl(g) + S(s)Hydrogen sulphide is oxidised to sulphur by the removal of hydrogen

Reduction

Reduction is the removal of oxygen or the addition of hydrogen. A
reducing agent is a substance that removes oxygen from or adds hydrogen to another substance. Extraction of metals from their oxide ores is a common example of reduction.

Some reduction reactions
ReactionExplanation
N2(g) + 3H2(g) → 2NH3(g)Nitrogen is reduced to ammonia by the addition of hydrogen
PbO(s) + H2(g) → H2O(g) + Pb(s)Lead oxide is reduced to lead by the removal of oxygen

Redox

Redox is short for REDuction and OXidation. A redox reaction is a reaction in which oxidation and reduction takes place at the same time. One substance is oxidised while the other is reduced.

Redox in terms of electron loss and gain

Oxidation and reduction can also be explained in terms of the movement of electrons.

Oxidation is the removal of electrons whilst reduction is the addition of electrons

An oxidising substance removes electrons from another substance

A reducing agent adds electrons to another substance

Extraction of Iron

Iron is extracted from iron ore by a process of reduction in the blast furnace. The main ores of iron are haematite (Fe2O3) and magnetite (Fe3O4). Carbon is used as a reducing agent.

Steel making

Oxygen Lance

Basic oxygen-lance furnace

Image source

Iron from the blast furnace is called cast iron or pig iron. It contains many impurities such as carbon, sulphur and phosphorus. It is purify in the oxygen-lance furnace where oxygen is blown into the molten iron at high pressure to oxidise the
impurities.

Pure iron is no good as a structural material because it is too soft, and stretches quite easily and also because it rusts very easily.

Adding small amounts of other elements produces an alloy of iron called steel. An alloy is a mixture of a metal and other elements. Alloys have many desirable properties not found in pure metals.

Oxidising agent warning

Globally Harmonized System of Classification and Labelling of Chemicals (GHS) pictogram for oxidizing substances