Grade 12 Physical Sciences · Chemical Change

Compare oxidising and reducing agent strength

Use the table of standard reduction potentials to decide which substance is oxidised or reduced, and whether a reaction will happen.

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

Electrochemistry Gr 12 : Galvanic cell (using the table)Kevinmathscience

Compare Strength of Oxidizing and Reducing AgentsOld School Chemistry

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Question 8.4 · May/June 2025 · Paper 2 · National (DBE) · 3 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)

8.4 Explain the answer to QUESTION 8.3 in terms of the relative strengths of the reducing agents.(3)

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More past paper questions: compare oxidising and reducing agent strength

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3. Question 8.2 · November 2025 · Paper 2 · National (DBE) · 2 marks
The diagram below represents a cell that operates initially under standard conditions.
8.2 Which ion concentration, $A ℓ^{3 +}$ (aq) or $Zn^{2 +}$ (aq), will increase? Give a reason for the answer.(2)
Show the memo (2 ticks)Memo
1. ✓
  Ion that increases $A ℓ^{3 +}$ / Aluminium ion
  1 mark · Compare oxidising and reducing agent strength
2. ✓
  ReasonA $ℓ$ is oxidised OR A $ℓ$ is a stronger reducing agent.
  1 mark · Compare oxidising and reducing agent strength
4. Question 8.1.4 · November 2024 · Paper 2 · National (DBE) · 3 marks
8.1 Dilute hydrochloric acid, HCℓ(aq), reacts with magnesium, Mg(s), at $25$ °C according to the following balanced equation:

$Mg(s) + 2 HC ℓ (aq) \to MgC ℓ_{2} (aq) + H_{2} (g)$

Answer the questions that follow.
8.1.4 Will dilute nitric acid, $HNO_{3}$ (aq), react with copper, Cu(s), at $25$ °C? Choose from YES or NO.

Explain the answer in terms of the relative strengths of the oxidising agents.(3)
Show the memo (3 ticks)Memo
1. ✓
  YesYes
  1 mark · Compare oxidising and reducing agent strength
2. ✓
  NO $_{3}^{-}$ is a stronger oxidising agent $NO_{3}^{-}$ / nitrate ion / nitric acid is a stronger oxidising agent
  1 mark · Compare oxidising and reducing agent strength
3. ✓
  than Cu $^{2 +}$ than $Cu^{2 +}$ / copper(II) ion (therefore Cu/copper will be oxidised to $Cu^{2 +}$ / copper(II) ion).
  1 mark · Compare oxidising and reducing agent strength
5. Question 1.10 · May/June 2024 · Paper 2 · National (DBE) · 2 marks
1.10 Which ONE of the following redox reactions is SPONTANEOUS under standard conditions?(2)
1. A $Br_{2} + 2 C ℓ^{-} \to 2 Br^{-} + C ℓ_{2}$
2. B $2 Fe^{3 +} + 2 I^{-} \to 2 Fe^{2 +} + I_{2}$
3. C $Ni^{2 +} + H_{2} \to Ni + 2 H^{+}$
4. D $Cu + Pb^{2 +} \to Cu^{2 +} + Pb$
Show the memo (1 tick)Memo
1. ✓
  Choose the correct optionA reaction is spontaneous when the oxidising agent is stronger (higher on Table 4A) than the oxidised form of the reducing agent. B: $Fe^{3 +}$ ( $+ 0, 77$ V) is a stronger oxidising agent than $I_{2}$ ( $+ 0, 54$ V), so $Fe^{3 +}$ oxidises $I^{-}$ . In A, C and D the oxidising agent ( $Br_{2}$ , $Ni^{2 +}$ , $Pb^{2 +}$ ) is weaker than the one it would have to form.
  
  Answer: B
  2 marks · Compare oxidising and reducing agent strength
6. Question 9.2.4 · 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.
9.2.4 Explain the answer to QUESTION 9.2.3 by referring to the relative strengths of the oxidising agents involved.(2)
Show the memo (2 ticks)Memo
1. ✓
  Water is a stronger oxidising agentWater/ $H_{2} O$ is a stronger oxidising agent (than $Na^{+}$ /sodium ion)
  
  OR: $Na^{+}$ /sodium ion is a weaker oxidising agent than water/ $H_{2} O$
  1 mark · Compare oxidising and reducing agent strength
2. ✓
  Water will be reducedand water/ $H_{2} O$ will be reduced.
  1 mark · Compare oxidising and reducing agent strength

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