Grade 12 Physical Sciences · Chemical Change

Write half-reactions

Write the oxidation or reduction half-reaction for a substance, with electrons on the correct side (Cu²⁺ + 2e⁻ → Cu).

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Electrochemistry How to Use Table 4B for Galvanic Cells | Grade 12 ChemistryMiss Martins Maths and Science

Writing Half-Reactions: Examples, Explanation, and PracticeWayne Breslyn (Dr. B.)

GCSE Chemistry - Redox Reactions - Displacement Reactions | Ionic Equations | Half EquationsCognito

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Question 9.2 · May/June 2025 · Paper 2 · National (DBE) · 2 marks

The simplified diagram below represents an electrolytic cell used to demonstrate the electrolysis of a concentrated sodium chloride solution, NaCℓ(aq).

X and Y are carbon electrodes. Diagram for this question

9.2 Write down the reduction half-reaction for this cell.(2)

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

More past paper questions: write half-reactions

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3. Question 8.5.2 · May/June 2025 · Paper 2 · National (DBE) · 2 marks
The simplified diagram below shows a cell that can be used to measure the standard electrode potential of the half-reaction represented by the equation below.

$Fe^{3 +} (aq) + e^{-} ⇌ Fe^{2 +} (aq)$
8.5 Write down the:
8.5.2 Half-reaction that occurs at electrode B(2)
Show the memo (1 tick)Memo
1. ✓
  Oxidation half-reaction $H_{2} \to 2 H^{+} + 2 e^{-}$
  2 marks · Write half-reactions
4. Question 9.2.2 · November 2024 · Paper 2 · National (DBE) · 2 marks
9.2 The simplified diagram below represents an electrolytic cell. The electrodes are made of carbon.

Answer the questions that follow.
9.2.2 Write down the PREDOMINANT oxidation half-reaction that takes place in this cell.(2)
Show the memo (1 tick)Memo
1. ✓
  Oxidation half-reaction $2 C ℓ^{-} \to C ℓ_{2} + 2 e^{-}$
  2 marks · Write half-reactions
5. Question 9.3.1 · May/June 2023 · Paper 2 · National (DBE) · 2 marks
The simplified electrolytic cell below is used to electroplate a metal spring. Zinc nitrate, $Zn(NO_{3})_{2}$ (aq), is used as an electrolyte and R is an electrode.
9.3 Write down the:
9.3.1 Equation for the half-reaction occurring at the metal spring(2)
Show the memo (1 tick)Memo
1. ✓
  Reduction half-reaction $Zn^{2 +} (aq) + 2 e^{-} \to Zn(s)$
  2 marks · Write half-reactions
6. Question 9.2 · November 2023 · Paper 2 · National (DBE) · 2 marks
An electrolytic cell is set up to purify a piece of copper that contains silver and zinc as impurities. A simplified diagram of the cell is shown below. Electrode R is impure copper.

During this electrolysis, only copper and zinc are oxidised (see QUESTION 9.5).
9.2 Write down the reaction taking place at electrode Q.(2)
Show the memo (1 tick)Memo
1. ✓
  Reduction half-reaction at Q $Cu^{2 +} (aq) + 2 e^{-} \to Cu(s)$
  2 marks · Write half-reactions

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