Grade 11 Physical Sciences · Chemical Change · Paper 2 (Chemistry)

Acid-Base and Redox Reactions Grade 11

Real Acid-Base and Redox Reactions past paper questions and answers from 2022 to 2025, with each memo split into the ticks examiners give. Try one, mark yourself, and see exactly which skill cost you marks.

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Question 1.8 · November 2025 · Paper 2 · Provincial · 2 marks

Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10) in the ANSWER BOOK, for example 1.11 E.

1.8 Consider the following equation:

(COOH)_{2}

(aq) +

H_{2} O

(

ℓ

) ⇌

(COO)_{2}^{2 -}

(aq) +

H_{3} O^{+}

(aq)

The bases in the above reaction are ...(2)

A $(COOH)_{2}$ and $H_{2} O$
B $(COO)_{2}^{2 -}$ and $H_{3} O^{+}$
C $H_{2} O$ and $(COO)_{2}^{2 -}$
D $(COOH)_{2}$ and $(COO)_{2}^{2 -}$

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More Acid-Base and Redox Reactions Grade 11 questions and answers

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4. Question 7.1.1 · November 2024 · Paper 2 · Provincial · 2 marks
7.1 Carbonic acid ionises in water according to the following balanced equation:

$H_{2} CO_{3} (aq) + H_{2} O (ℓ) ⇌ HCO_{3}^{-} (aq) + H_{3} O^{+} (aq)$
7.1.1 Define an acid according to the Arrhenius theory.(2)
Show the memo (1 tick)Memo
1. ✓
  Arrhenius definition of an acidAn acid is a substance that produces hydrogen ions ( $H^{+}$ ) / hydronium ions ( $H_{3} O^{+}$ ) when it dissolves in water.
  2 marks · Define acid and base terms
5. Question 8.1 · November 2024 · Paper 2 · Provincial · 2 marks
8.1 Define a Brønsted-Lowry base.(2)
Show the memo (1 tick)Memo
1. ✓
  Definition of a baseA base is a proton / $H^{+}$ ion acceptor.
  2 marks · Define acid and base terms
6. Question 1.8 · November 2023 · Paper 2 · Provincial · 2 marks
1.8 Which of the following is NOT a conjugate acid-base pair?(2)
1. A HCℓ and Cℓ $^{-}$
2. B $HCO_{3}^{-}$ and $H_{2} CO_{3}$
3. C $HSO_{4}^{-}$ and $H_{2} SO_{4}$
4. D $OH^{-}$ and $H_{3} O^{+}$
Show the memo (1 tick)Memo
1. ✓
  Correct optionA conjugate pair differs by exactly ONE proton ( $H^{+}$ ).
  A: HCℓ → Cℓ $^{-}$ (one $H^{+}$ )
  B: $H_{2} CO_{3}$ → $HCO_{3}^{-}$ (one $H^{+}$ )
  C: $H_{2} SO_{4}$ → $HSO_{4}^{-}$ (one $H^{+}$ )
  D: $H_{3} O^{+}$ and $OH^{-}$ differ by TWO protons, so they are not a conjugate pair.
  
  Answer: D
  2 marks · Identify conjugate acid-base pairs
7. Question 1.2 · November 2023 · Paper 2 · Provincial · 2 marks
1.2 Which ONE of the following ions can act as an ampholyte?(2)
1. A $HCO_{3}^{-}$
2. B $NH_{4}^{+}$
3. C $NO_{3}^{-}$
4. D $H_{3} O^{+}$
Show the memo (1 tick)Memo
1. ✓
  Correct optionAn ampholyte can both donate and accept a proton. $HCO_{3}^{-}$ can donate $H^{+}$ (forming $CO_{3}^{2 -}$ ) and accept $H^{+}$ (forming $H_{2} CO_{3}$ ). $NH_{4}^{+}$ and $H_{3} O^{+}$ can only donate; $NO_{3}^{-}$ cannot donate a proton.
  
  Answer: A
  2 marks · Identify conjugate acid-base pairs
8. Question 7.1.1 · November 2023 · Paper 2 · Provincial · 2 marks
7.1 Sulphuric acid is a strong acid and an example of a diprotic acid.

Answer the questions that follow.
7.1.1 Define an acid in terms of the Lowry-Brønsted theory.(2)
Show the memo (1 tick)Memo
1. ✓
  Lowry-Brønsted definition of an acidAn acid is a proton ( $H^{+}$ ion) donor.
  2 marks · Define acid and base terms
9. Question 8.1.1 · November 2023 · Paper 2 · Provincial · 2 marks
8.1 Consider the following acid-base reaction that occurs in an indicator, HIn:

$HIn(aq) + H_{2} O(ℓ) ⇌ In^{-} (aq) + X(aq)$
8.1.1 Define an acid according to the Lowry-Brønsted theory.(2)
Show the memo (1 tick)Memo
1. ✓
  Lowry-Brønsted acidAcid is a proton / $H^{+}$ -ion donor
  2 marks · Define acid and base terms
10. Question 1.5 · November 2022 · Paper 2 · Provincial · 2 marks
1.5 Consider the INCOMPLETE reaction below:

$X + HC ℓ \to Salt + H_{2} O$

Which ONE of the following is CORRECT regarding compound X?

Compound X is a(n) …(2)
1. A carbonate.
2. B metal.
3. C metal oxide.
4. D acid.
Show the memo (1 tick)Memo
1. ✓
  Correct optionAcid + metal oxide → salt + water. A carbonate would also give $CO_{2}$ , and a metal would give hydrogen gas instead of water. An acid does not neutralise HCℓ.
  
  Answer: C
  2 marks · Write acid-base reaction equations

Acid-Base and Redox Reactions Grade 11 videos

Short lessons from South African teachers first. Videos load only when you tap play, to save your data.

Grade 11 Acids and Bases: Type of reactions Introduction | Defining acids and basesMiss Martins Maths and Science

Conjugate acid base pairs: Grade 11 and 12 Acids and BasesMiss Martins Maths and Science

Common Acid Base Reactions Grade 11Kevinmathscience

What Are Indicators & How Do We Use Them? | Chemical Tests | Chemistry | FuseSchoolFuseSchool - Global Education

Grade 12 Acids and Bases Grade 11 Revision PART 2: Strong/Weak vs Concentrated/diluteMiss Martins Maths and Science

Acids and Bases Grade 12: PH calculationsKevinmathscience

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