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Oxidation-Reduction (Redox) Reactions

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Oxidation-reduction (redox) reactions transfer electrons. One species is oxidized (loses electrons, oxidation state rises) and another is reduced (gains electrons, oxidation state falls). Splitting the reaction into half-reactions — one for oxidation, one for reduction — tracks the electrons explicitly.

UNIT 4 TOPIC 4.9 • OXIDATION-REDUCTION (REDOX) REACTIONS ELECTRON TRACKER OVERALL REACTION Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) electrons transfer from Zn to Cu²⁺ OXIDATION HALF-REACTION Zn → Zn²⁺ + 2e⁻ oxidation number: 0 → +2 loses electrons Zn Zn²⁺ 2e⁻ REDUCTION HALF-REACTION Cu²⁺ + 2e⁻ → Cu oxidation number: +2 → 0 gains electrons Cu²⁺ Cu 2e⁻ BALANCE WITH HALF-REACTIONS 1 split into oxidation and reduction 2 balance atoms and charge in each half 3 make electrons equal 4 add halves and cancel electrons OIL RIG Oxidation Is Loss, Reduction Is Gain of electrons. AP Chemistry · Unit 4 · Chemical Reactions
Redox reactions transfer electrons. When zinc metal reacts with copper ions, zinc gives up electrons (oxidation) and copper ions gain them (reduction). Splitting the reaction into oxidation and reduction half-reactions tracks where the electrons go.
Electron Tracker · Open the sandbox →

The core skill is following the electrons through changes in oxidation state: which species loses them (is oxidized) and which gains them (is reduced). The two always happen together — no oxidation without a matching reduction.

The work

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Lesson
Redox Reactions ›

Redox reactions transfer electrons, oxidizing one species and reducing another. The lesson tracks oxidation states and half-reactions, then closes with a ten-scenario check.

Skill check · 10 scenarios
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Diagnostic
10-item topic check ›

Ten items on redox reactions: identifying oxidation and reduction from electron transfer and oxidation-state changes, and reading the half-reactions.

Not started · 10 items · ~15 min
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Targeted Practice
Drill a single misconception ›

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions
Diagnostic first