Balancing redox and agents
Introduced| English | Meaning |
|---|---|
| disproportionation/ˌdɪsprəˈpɔːʃəneɪʃn/ | A reaction in which the same element is both oxidised and reduced. |
| reducing agent/rɪˈdjuːsɪŋ ˈeɪdʒənt/ | A substance that donates electrons to another substance and is itself oxidised. |
| oxidised/ˈɒksɪdaɪzd/ | oxidised |
| reduced/rɪˈdjuːst/ | reduced |
| oxidising agent/ˈɒksɪdaɪzɪŋ ˈeɪdʒənt/ | A substance that accepts electrons from another substance and is itself reduced. |
Balancing the electron books
- Oxidation numbers help balance redox equations.
- A special case is disproportionation 歧化.
- And every redox reaction has an oxidising and a reducing agent 还原剂.
An oxidising agent is itself reduced during a reaction.
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It gains the electrons lost by the other species.
Balancing with oxidation numbers
- find the element whose number rises (oxidised 被氧化) and the one whose number falls (reduced 被还原).
- the total rise = total fall (every electron lost is gained somewhere).
- choose the ratio so they match, then balance the rest.
Redox is electron transfer: the reducing agent is oxidised, the oxidising agent 氧化剂 is reduced
Counting the electrons moved
Watch the electrons hand over: the oxidising agent takes them, the reducing agent gives them — balance the half-equations so the electrons cancel.
When balancing a redox equation using oxidation numbers:
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Every electron lost is gained, so the total increase in oxidation number equals the total decrease.
Disproportionation
- Disproportionation is when the same element is both oxidised and reduced at once.
- E.g. chlorine + cold water: some Cl atoms are reduced to $\text{Cl}^{-}$ ($-1$) and others oxidised to $\text{ClO}^{-}$ ($+1$).
Disproportionation is a reaction in which:
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In disproportionation one element goes both up and down in oxidation number (e.g. Cl₂ → Cl⁻ and ClO⁻).
Match each redox term to its meaning.
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Each item links the term to its correct meaning.
Oxidising and reducing agents
- an oxidising agent takes electrons from another species — so it is itself reduced.
- a reducing agent gives electrons to another species — so it is itself oxidised.
An oxidising agent:
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An oxidising agent removes electrons from another species, so it gains electrons and is reduced itself.
A reducing agent:
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A reducing agent donates electrons, causing reduction of the other species while being oxidised itself.
You've got it
- balance redox by making the total rise = total fall in oxidation number
- disproportionation: the same element is both oxidised and reduced (Cl₂ → Cl⁻ + ClO⁻)
- oxidising agent takes electrons (itself reduced); reducing agent gives electrons (itself oxidised)