Oxidation and Reduction
DEFINITIONS OF OXIDATION AND REDUCTION (REDOX)
This page looks at the various definitions of oxidation and reduction (redox) in terms of the transfer of oxygen, hydrogen and electrons. It also explains the terms oxidising agent and reducing agent.
Oxidation and reduction in terms of oxygen transfer
Definitions
• Oxidation is gain of oxygen. • Reduction is loss of oxygen.
For example, in the extraction of iron from its ore:
[pic]
Because both reduction and oxidation are going on side-by-side, this is known as a redox reaction.
Oxidising and reducing agents
An oxidising agent is substance which oxidises something else. In the above example, the iron(III) oxide is the oxidising agent.
A reducing agent reduces something else. In the equation, the carbon monoxide is the reducing agent. • Oxidising agents give oxygen to another substance. • Reducing agents remove oxygen from another substance.
Oxidation and reduction in terms of hydrogen transfer
These are old definitions which aren't used very much nowadays. The most likely place you will come across them is in organic chemistry.
Definitions
• Oxidation is loss of hydrogen. • Reduction is gain of hydrogen.
Notice that these are exactly the opposite of the oxygen definitions.
For example, ethanol can be oxidised to ethanal:
[pic]
You would need to use an oxidising agent to remove the hydrogen from the ethanol. A commonly used oxidising agent is potassium dichromate(VI) solution acidified with dilute sulphuric acid.
[pic]
Note: The equation for this is rather complicated for this introductory page. If you are interested, you will find a similar example (ethanol to ethanoic acid) on the page dealing with writing equations for redox reactions.
[pic]
Ethanal can also be reduced back to ethanol again by adding hydrogen to it. A possible reducing agent is sodium tetrahydridoborate, NaBH4. Again the equation is too complicated to be worth bothering about at this point.
[pic]
This page looks at the various definitions of oxidation and reduction (redox) in terms of the transfer of oxygen, hydrogen and electrons. It also explains the terms oxidising agent and reducing agent.
Oxidation and reduction in terms of oxygen transfer
Definitions
• Oxidation is gain of oxygen. • Reduction is loss of oxygen.
For example, in the extraction of iron from its ore:
[pic]
Because both reduction and oxidation are going on side-by-side, this is known as a redox reaction.
Oxidising and reducing agents
An oxidising agent is substance which oxidises something else. In the above example, the iron(III) oxide is the oxidising agent.
A reducing agent reduces something else. In the equation, the carbon monoxide is the reducing agent. • Oxidising agents give oxygen to another substance. • Reducing agents remove oxygen from another substance.
Oxidation and reduction in terms of hydrogen transfer
These are old definitions which aren't used very much nowadays. The most likely place you will come across them is in organic chemistry.
Definitions
• Oxidation is loss of hydrogen. • Reduction is gain of hydrogen.
Notice that these are exactly the opposite of the oxygen definitions.
For example, ethanol can be oxidised to ethanal:
[pic]
You would need to use an oxidising agent to remove the hydrogen from the ethanol. A commonly used oxidising agent is potassium dichromate(VI) solution acidified with dilute sulphuric acid.
[pic]
Note: The equation for this is rather complicated for this introductory page. If you are interested, you will find a similar example (ethanol to ethanoic acid) on the page dealing with writing equations for redox reactions.
[pic]
Ethanal can also be reduced back to ethanol again by adding hydrogen to it. A possible reducing agent is sodium tetrahydridoborate, NaBH4. Again the equation is too complicated to be worth bothering about at this point.
[pic]