Redox I | Edexcel A-Level Chemistry (9CH0)
Redox I
- 35 questions
- 2 subtopics
- Topics 2, 3 and 5, examined on all three papers
- Paper 1, Paper 2 and Paper 3
Covers oxidation numbers and the rules for assigning them, the definitions of oxidation and reduction in terms of electrons, disproportionation, and building ionic equations from half-equations..
It covers oxidation numbers and oxidation, reduction, disproportionation and half-equations.
Sample questions from Redox I
Answer each one closed book first, then open the answer.
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Oxidation numbers
What is the oxidation number of fluorine in its compounds?
Show the answer
Always -1. -
Oxidation numbers
In Cr₂O₇²⁻, what oxidation number does chromium take?
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+6 (seven oxygens at -2 give -14; ion charge -2, so the two Cr total +12, i.e. +6 each). -
Oxidation, reduction, disproportionation and half-equations
In general, how do metals form ions, and what happens to their oxidation number?
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They lose electrons to form positive ions, so their oxidation number increases. -
Oxidation, reduction, disproportionation and half-equations
What is an ionic half-equation?
Show the answer
An equation showing the electrons lost or gained by one species in a redox reaction.
The 2 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Oxidation numbers | Recall questions on the rules for assigning oxidation numbers, on working them out in ions and compounds, and on what a Roman numeral in a name means. | 15 |
| Oxidation, reduction, disproportionation and half-equations | Recall questions on defining oxidation and reduction by electron transfer, identifying oxidising and reducing agents, spotting disproportionation, and combining half-equations. | 20 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel A-Level Chemistry Active Recall Guide
Every topic, not just this one. 1,534 questions with their answers.