Grade 12 Physical Sciences · Chemical Change · Paper 2 (Chemistry)

Acids and Bases Grade 12

Real Acids and Bases past paper questions and answers from 2023 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 1.7 · November 2025 · Paper 2 · National (DBE) · 2 marks

Various options are provided as possible answers to the following questions. Each question has only ONE correct answer.

1.7 The products for the reaction between a metal oxide and an acid are ...(2)

A a salt and water.
B a salt and hydrogen gas.
C a salt and carbon dioxide.
D a salt, water and carbon dioxide.

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

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More Acids and Bases Grade 12 questions and answers

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4. Question 5.2.2 · November 2025 · Paper 2 · National (DBE) · 5 marks
5.2 Carbon monoxide, CO(g), reacts with oxygen, $O_{2}$ (g), to form carbon dioxide, $CO_{2}$ (g), in a sealed container according to the balanced equation:

$2 CO(g) + O_{2} (g) \to 2 CO_{2} (g)$

The graph below shows the concentration of $O_{2}$ (g) versus time.

Answer the questions that follow.
5.2.2 The reaction takes place in a $3$ dm $^{3}$ container. Calculate the average rate (in mol·s $^{- 1}$ ) at which $CO_{2}$ (g) is formed in the first 10 s.(5)
Show the memo (5 ticks)Memo
1. ✓
  (a) Calculate the change in concentrationRate $= - \frac{Δ c ( O _{2} )}{Δ t}$
  $= - \frac{( 0 , 15 - 0 , 27 )}{\dots}$
  1 mark · Calculate reaction rate
2. ✓
  (b) Substitute 10 s $= - \frac{( 0 , 15 - 0 , 27 )}{10 - 0}$
  $= 0, 012$ mol·dm $^{- 3}$ ·s $^{- 1}$
  1 mark · Calculate reaction rate
3. ✓
  (c) Multiply by 3 dm3Rate ( $O_{2}$ ) in mol·s $^{- 1}$ $= c V = (0, 012) (3) = 0, 036$ mol·s $^{- 1}$
  1 mark · Calculate concentration of a solution
4. ✓
  (d) Use the mol ratioRate ( $CO_{2}$ ) $= 2 \times$ rate ( $O_{2}$ ) $= 2 \times 0, 036$
  1 mark · Use the mole ratio
5. ✓
  (e) Final answer $= 0, 072$ (mol·s $^{- 1}$ )
  1 mark · Use the mole ratio
5. Question 1.7 · November 2024 · Paper 2 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10) in the ANSWER BOOK, e.g. 1.11 E.
1.7 The table below shows the ionisation constants, $K_{a}$ , for two acids at $25$ °C.

Consider the following statements for these two acids when they have equal concentration at $25$ °C:

(i) Both are weak acids.
(ii) Butanoic acid is a stronger acid than ethanoic acid.
(iii) The butanoic acid solution has a lower concentration of hydronium ion, $H_{3} O^{+}$ (aq), than the ethanoic acid solution.

Which of the above statements are TRUE?(2)
1. A (i) and (ii) only
2. B (i) and (iii) only
3. C (ii) and (iii) only
4. D (i), (ii) and (iii)
Show the memo (1 tick)Memo
1. ✓
  Correct option(i) Both $K_{a}$ values are much smaller than 1, so both acids are weak. TRUE.
  (ii) Ethanoic acid has the larger $K_{a}$ ( $1, 8 \times 1 0^{- 5}$ against $1, 5 \times 1 0^{- 5}$ ), so ethanoic acid is the stronger acid. FALSE.
  (iii) Butanoic acid ionises less, so at equal concentration it produces fewer $H_{3} O^{+}$ ions. TRUE.
  
  Answer: B
  2 marks · Compare strong and weak acids
6. Question 7.1 · November 2024 · Paper 2 · National (DBE) · 2 marks
Hydrated potassium carbonate, $K_{2} CO_{3} \cdot x H_{2} O$ , is a WEAK BASE. A solution is prepared by dissolving some of this solid in water.
7.1 Define the term weak base.(2)
Show the memo (2 ticks)Memo
1. ✓
  Ionises incompletely in waterWeak bases dissociate/ionise incompletely/partially in water
  1 mark · Define acid and base terms
2. ✓
  Low concentration of OH $^{-}$ ionsto form a low concentration of hydroxide/ $OH^{-}$ ions.
  1 mark · Define acid and base terms
7. Question 1.7 · May/June 2024 · Paper 2 · National (DBE) · 2 marks
1.7 Which ONE of the following shows the PRODUCTS for the reaction of oxalic acid with sodium hydroxide?(2)
1. A $(COO)_{2} Na_{2} (aq) + H_{2} O (ℓ) + CO_{2} (g)$
2. B $(COO)_{2} Na_{2} (aq) + H_{2} O (ℓ)$
3. C $CH_{3} COONa(aq) + H_{2} O (ℓ)$
4. D $CH_{3} COONa(aq) + H_{2} O (ℓ) + CO_{2} (g)$
Show the memo (1 tick)Memo
1. ✓
  Choose the correct optionOxalic acid, $(COOH)_{2}$ , is neutralised by a hydroxide: acid + base $\to$ salt + water. The salt is sodium oxalate, $(COO)_{2} Na_{2}$ . No $CO_{2}$ forms because there is no carbonate.
  
  Answer: B
  2 marks · Write acid-base reaction equations
8. Question 4.1.3 · May/June 2024 · Paper 2 · National (DBE) · 2 marks
4.1 In an experiment, a test tube containing methanol, propanoic acid and a catalyst is heated in a water bath, as shown below.

Write down:
4.1.3 TWO reasons why the use of a water bath is preferred in this experiment(2)
Show the memo (2 ticks)Memo
1. ✓
  First reasonAlcohol/methanol/reactant is flammable/catches fire easily.
  1 mark · Describe and evaluate an experiment
2. ✓
  Second reasonTo heat evenly / a steady, controlled, gradual increase in temperature. (OR: Alcohol/methanol will evaporate too quickly/is volatile.)
  1 mark · Describe and evaluate an experiment
9. Question 1.7 · November 2023 · Paper 2 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10).
1.7 Nitric acid, $HNO_{3}$ (aq), and ethanoic acid, $CH_{3} COOH$ (aq), of equal volumes and concentrations are compared.

Consider the following statements regarding these solutions:

(i) They have different pH values.
(ii) Both have the same electrical conductivity.
(iii) Both solutions require the same number of moles of KOH(aq) for complete neutralisation.

Which of the above statement(s) is/are TRUE?(2)
1. A (i) only
2. B (i) and (ii) only
3. C (i) and (iii) only
4. D (ii) and (iii) only
Show the memo (1 tick)Memo
1. ✓
  Correct option(i) $HNO_{3}$ is a strong acid (ionises completely) and $CH_{3} COOH$ is weak (ionises partly), so $HNO_{3}$ has a higher $[H_{3} O^{+}]$ and a lower pH. TRUE.
  (ii) $HNO_{3}$ forms more ions, so it conducts better. FALSE.
  (iii) Both are monoprotic and have the same number of moles of acid, so they need the same number of moles of KOH. TRUE.
  
  Answer: (i) and (iii)
  
  Answer: C
  2 marks · Compare strong and weak acids
10. Question 5.3 · November 2023 · Paper 2 · National (DBE) · 3 marks
The reaction between EXCESS dilute hydrochloric acid and sodium thiosulphate is used to investigate factors that influence reaction rate.

$Na_{2} S_{2} O_{3} (aq) + 2 HCl(aq) \to 2 NaCl(aq) + S(s) + H_{2} O (ℓ) + SO_{2} (g)$

The concentration of HCl(aq) used is $1$ mol·dm $^{- 3}$ . The same volume of HCl(aq) is used in each run.

The time taken for the cross on the paper under the flask to become invisible is measured.

The table below summarises the reaction conditions and results of the experiment.
5.3 Calculate the value of P in the table.(3)
Show the memo (3 ticks)Memo
1. ✓
  Substitute 0,03 and 0,13 $c = \frac{n}{V}$
  $0, 13 = \frac{n}{0 , 03}$
  $n = 3, 9 \times 1 0^{- 3}$ mol
  1 mark · Calculate concentration of a solution
2. ✓
  Substitute 0,05 $c = \frac{n}{V} = \frac{3 , 9 \times 1 0 ^{- 3}}{0 , 05}$
  1 mark · Calculate concentration of a solution
3. ✓
  Final answer $P = 0, 078$ mol·dm $^{- 3}$
  1 mark · Calculate concentration of a solution

Acids and Bases Grade 12 videos

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

Concentration of solutions ChemistryMiss Martins Maths and Science

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Common Acid Base Reactions Grade 11Kevinmathscience

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

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