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Oxidation and Reduction

How fireworks work? How fireworks work? Fireworks have been a traditional part of festive celebrations since they were invented by Chinese thousands of years ago. The chemical reactions that take place in firecrackers are REDOX reactions. Firecrackers consist of gunpowder, oxidants (potassium nitrate, potassium chlorate), reductants (charcoal, sulfur) and metals such as Cu, Na, Ba, Sr, Ti etc. to get colored sparkles: typically blue, golden yellow, green, red and white. The reaction is accompanied by evolution of heat, sound and light.

Learning Objectives

After completing the topic, the student will be able to:

  • Define reduction and oxidation (redox in short)reactions.
  • Represent a redox reaction in terms of electron transfer.
  • Define oxidizing and reducing agents and give examples.
  • Identify the oxidizing or reducing agent in a given reaction.
  • Define oxidation number and calculate the change in valency or oxidation number of species in a redox reaction.
  • Balance a redox reaction using ion–electron method.
  • Discuss everyday examples involving a redox process.
Simple understanding of oxidation and reduction reactions Simple understanding of oxidation and reduction reactions Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.
Oxidation and Reduction

In chemical reactions, inter molecular bonds between reactants are broken and new bonds are made in the product molecules. This transformation is the simple rearrangement of electrons. Reactions that involve the transfer of one or more electrons from one reactant to another are called oxidation–reduction reactions.

Oxidation is the process in which electrons are removed from an atom or ion.
Reduction involves the addition of electrons to an atom or ion.

Alternately, oxidation reaction would be an addition of oxygen to a substance.
Reduction reaction would mean removal of oxygen from a substance.

Burning of coal is an oxidation process Burning of coal and magnesium Burning of coal (a) and magnesium (b) are rapid oxidation processes while rusting of iron is a slow oxidation process.
Examples for oxidation process

Since years, we have been burning coal to get heat. We also know that for burning of coal we need supply of fresh air. What happens when coal burns? The oxygen from the air reacts with carbon in coal. We can represent this reaction by the chemical equation as follows:

C + O2 CO2 (g)

Carbon dioxide is the product. If sufficient supply of fresh air is not available, the reaction may be as follows:

2C + O2 2CO (g)

Carbon monoxide is the product. Both the products, CO2 and CO, being gases escape into the atmosphere.

Another common experience is burning of magnesium wire, which is popular in the fireworks.

2Mg + O2 2MgO
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