AQA · Chemistry · 8462
GCSE Chemistry (AQA): Redox Reactions
Topic 4 — Chemical Changes. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Redox Reactions - Displacement Reactions | Ionic Equations | Half Equations"; each card deep-links to the moment in the video it came from. Lesson 4.09 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_4.09.
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What does an ionic equation show?
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Only the particles that actually take part in the reaction and change in some way; spectator ions are omitted.
Why must oxidation and reduction happen together?
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If one substance loses electrons, another substance must gain them.
Write the half equation for Fe²⁺ being reduced to iron.
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Fe²⁺ + 2e⁻ → Fe. The electrons go on the left because the ion gains them.
Is a magnesium atom losing two electrons to form Mg²⁺ oxidised or reduced?
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Oxidised — oxidation is the loss of electrons.
In terms of oxygen, what are oxidation and reduction?
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Oxidation is the gaining of oxygen; reduction is the loss of oxygen.
What is a displacement reaction?
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A reaction in which a more reactive metal displaces a less reactive metal from its compound.
When magnesium reacts with dilute acid, what happens to the H⁺ ions?
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They are reduced — each gains an electron to form neutral hydrogen atoms, producing hydrogen gas.
What are the products when calcium is added to iron sulfate solution?
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Calcium sulfate solution and solid iron, which precipitates out — calcium is more reactive than iron.
How can you check a half equation is correct?
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The overall charge must be the same on both sides; if it isn't, the electrons are on the wrong side.
Ions that do not change or exchange electrons during a reaction are called ? ions.
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spectator
Write the half equation for calcium being oxidised to Ca²⁺.
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Ca → Ca²⁺ + 2e⁻. The electrons are products because the atom loses them.
What is a redox reaction?
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A reaction in which oxidation and reduction take place at the same time.
The mnemonic OIL RIG stands for oxidation is ?, reduction is gain — of electrons.
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loss
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