Half-equations and balancing redox
Practice Flashcards
Flip to reveal answersWhat is a half-equation?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 11 Flashcards — Half-equations and balancing redox
Sign up free to track progress and get spaced-repetition review schedules.
Question
What is a half-equation?
Answer
An equation showing **just the oxidation or just the reduction** part of a redox reaction, with the electrons (e⁻) included.
Question
Where do electrons go in an oxidation half-equation?
Answer
On the **right** (product) side — oxidation is **loss** of electrons.
Question
Where do electrons go in a reduction half-equation?
Answer
On the **left** (reactant) side — reduction is **gain** of electrons.
Question
What does OIL RIG stand for?
Answer
**O**xidation **I**s **L**oss, **R**eduction **I**s **G**ain (of electrons).
Question
How do you balance a half-equation?
Answer
Balance the **atoms** first, then add **electrons** to the more positive side so the **charge** balances.
Question
Half-equation for Zn → Zn²⁺?
Answer
$\text{Zn} \rightarrow \text{Zn}^{2+} + 2e^{-}$ — an oxidation (loses 2e⁻).
Question
Half-equation for Cu²⁺ → Cu?
Answer
$\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu}$ — a reduction (gains 2e⁻).
Question
How do you combine two half-equations?
Answer
**Multiply** so both transfer the same number of electrons, then **add** them and **cancel** the e⁻.
Question
Why multiply a half-equation before combining?
Answer
So the **electrons lost equal the electrons gained** — they must cancel exactly in the overall equation.
Question
Final check on a combined redox equation?
Answer
Both the **atoms** and the **total charge** must balance, with **no electrons** left over.
Question
Overall equation for Zn + Cu²⁺?
Answer
$\text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}$ — both halves transfer 2e⁻, which cancel.
Read the notes
Full study notes for Half-equations and balancing redox
Topic 6.2 hub
Electron transfer reactions
More from Topic 6.2
All flashcards in this topic
Chemistry exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free