AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Reduction is the process of electron gain and reducing agents are electron…
Full specification wording
Oxidation, reduction and redox equations: Reduction is the process of electron gain and reducing agents are electron donors.
Reduction is gain of electrons, and the reducing agent is the species that supplies them, so it is itself oxidised.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Reduction is gain of electrons, and the reducing agent is the species that supplies them, so it is itself oxidised. The rule of thumb is that the agent is always named for what it does to its partner, not for what happens to it. Reduction lowers the oxidation state of the species reduced. Reactive metals are good reducing agents because they lose electrons readily, and among the halides the iodide ion is the strongest reducing agent, which is why it alone is able to reduce sulfur in concentrated sulfuric acid as far as hydrogen sulfide. Disproportionation is the special case where one element is both oxidised and reduced in the same reaction, as chlorine is when it reacts with water to give chloride and chlorate(I) ions.
What earns the marks
- Defining reduction as gain of electrons.
- Defining a reducing agent as an electron donor.
- Identifying a reducing agent from a fall in the oxidation state of the species it reacts with.
- Explaining disproportionation as one element being both oxidised and reduced in the same reaction.
Common mistakes and how to put them right
Swapping the agents, so the species reduced is called the reducing agent.
Defining reduction as loss of oxygen only, which fails for electron transfer between ions.
Writing that a reducing agent gains electrons.
Missing disproportionation because the element appears twice on the product side.
Assuming the strongest reducing agent is the most reactive metal in every context, without reference to the reaction.
Exam tips
- Write the two half equations out; the one showing electrons on the left is the reduction.
- For disproportionation, quote the oxidation state of the element in all three species to prove both changes.
- Say electron donor rather than gives away electrons when a definition is asked for.
Try the lesson
The start of the Oxidation, reduction and redox equations: Reduction is the process of electron gain and reducing agents are electron donors. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement correctly describes the process of reduction in a chemical reaction?
Listen
Reduction is gain of electrons, and the reducing agent is the species that supplies them, so it is itself oxidised. The rule of thumb is that the agent is always named for what it does to its partner, not for what happens to it. Reduction lowers the oxidation state of the species reduced. Reactive metals are good reducing agents because they lose electrons readily, and among the halides the iodide ion is the strongest reducing agent, which is why it alone is able to reduce sulfur in concentrated sulfuric acid as far as hydrogen sulfide. Disproportionation is the special case where one element is both oxidised and reduced in the same reaction, as chlorine is when it reacts with water to give chloride and chlorate(I) ions. A strong answer earns marks for these points. defining reduction as gain of electrons. defining a reducing agent as an electron donor. identifying a reducing agent from a fall in the oxidation state of the species it reacts with. explaining disproportionation as one element being both oxidised and reduced in the same reaction. Exam tip: Write the two half equations out; the one showing electrons on the left is the reduction.
Key words
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reduction
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reducing agents
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strength of halide reducing agents
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disproportionation
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See every definition
- reduction
- The process of electron gain, which lowers the oxidation state of the species reduced.
- reducing agents
- Electron donors that supply the electrons, so the agent is itself oxidised.
- strength of halide reducing agents
- Among the halides the iodide ion is the strongest reducing agent, which is why it alone is able to reduce sulfur in concentrated sulfuric acid as far as hydrogen sulfide.
- disproportionation
- The special case where one element is both oxidised and reduced in the same reaction.
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