Oxidation and Reduction in Term of Changes of Oxidation State
Oxidation involves an increase in oxidation state
Reduction involves a decrease in oxidation state
- Another way to determine oxidation and reduction is to see the change of the oxidation state after a reaction.
- An atom is said to be oxidised when its oxidation state increases.
- An atom is said to be reduced when its oxidation state decreases.
Example:
- The magnesium’s oxidation state has increased by 2, from 0 to +2. Therefore, it has been oxidised.
- The hydrogen’s oxidation state has decreased by 1, from +1 to 0. Therefore it has been reduced.
- The chlorine is in the same oxidation state on both sides of the equation – it hasn’t been oxidised nor reduced.
Example:
There is no change of oxidation state for all elements. This isn’t a redox reaction.
Example:
- In this example, we can see that the oxidation state of chlorine has increased and also decreased.
- Chlorine is oxidised and reduced, at the same time.
- This is a good example of a disproportionation reaction. A disproportionation reaction is one in which a single substance is both oxidised and reduced.