Grade 11 Physical Sciences · Paper 2 (Chemistry)

Chemical Change Grade 11

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Question 1.5 · 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.

1.5 Consider the following statement regarding the activated complex during a chemical reaction:

(I) The activation energy must be overcome to reach the activated complex.
(II) It is the unstable transition state from reactants to products.
(III) It is the energy released or absorbed during a chemical reaction.

Which of the above statement(s) is/are CORRECT about the activated complex?(2)

A II and III only
B II only
C I and II only
D I only

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What's in Chemical Change Grade 11

Each skill is one thing a memo gives a tick for. Tap a skill for its own questions, notes and videos.

Stoichiometry49 past paper questions

Energy and Chemical Change15 past paper questions

Types of Reactions24 past paper questions

More Chemical Change Grade 11 questions and answers

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1. Question 2.3.2 · November 2025 · Paper 2 · National (DBE) · 5 marks
The letters A to G in the table below represent organic compounds.
2.3 Compound E, $C_{3} H_{8}$ (g), reacts with oxygen, $O_{2}$ (g), according to the balanced equation:

$C_{3} H_{8} (g) + 5 O_{2} (g) \to 3 CO_{2} (g) + 4 H_{2} O(g)$

Initially $8$ cm $^{3}$ of compound E and $50$ cm $^{3}$ of oxygen were injected into a container of adjustable volume and allowed to react, as shown below.

Answer the questions that follow.
2.3.2 Calculate the TOTAL volume of the GASES present in the container at the end of the reaction.(5)
Show the memo (5 ticks)Memo
1. ✓
  (a) Volume of O2 used (with volume of C3H8) $V (O_{2})_{used} = 5 V (C_{3} H_{8}) = (5) (8) = 40$ cm $^{3}$
  1 mark · Use the mole ratio
2. ✓
  (b) Volumes of CO2 and H2O produced $V (CO_{2})_{formed} = 3 V (C_{3} H_{8}) = (3) (8) = 24$ cm $^{3}$
  $V (H_{2} O)_{formed} = 4 V (C_{3} H_{8}) = (4) (8) = 32$ cm $^{3}$
  1 mark · Use the mole ratio
3. ✓
  (c) Volume of O2 remaining $V (O_{2})_{unused} = 50 - 40 = 10$ cm $^{3}$
  1 mark · Identify the limiting reagent
4. ✓
  (d) Addition of the three volumesVolume of gas in the container $= 10 + 24 + 32$
  1 mark · Identify the limiting reagent
5. ✓
  (e) Final answerTotal volume of gas in the container $= 66$ cm $^{3}$ (or $0, 066$ dm $^{3}$ )
  1 mark · Identify the limiting reagent
2. Question 5.1 · November 2024 · Paper 2 · Provincial · 2 marks
Consider the decomposition reaction of dinitrogen pentoxide:

$2 N_{2} O_{5} (g) \to 2 N_{2} O_{4} (g) + O_{2} (g)$

The table below shows the different energies for the above reaction.
5.1 Define the term activation energy.(2)
Show the memo (1 tick)Memo
1. ✓
  Definition of activation energyThe minimum energy needed for a reaction to take place.
  2 marks · Define rate and energy terms
3. Question 1.6 · November 2024 · Paper 2 · Provincial · 2 marks
1.6 Which ONE of the following is the conjugate acid of $HPO_{4}^{2 -}$ ?(2)
1. A $PO_{4}^{3 -}$
2. B $H_{2} PO_{4}^{-}$
3. C $H_{3} PO_{4}$
4. D $H_{2} PO_{4}^{2 -}$
Show the memo (1 tick)Memo
1. ✓
  Conjugate acid: add one protonA conjugate acid is formed when a base gains ONE proton ( $H^{+}$ ). Adding $H^{+}$ adds one H and raises the charge by $+ 1$ :
  $HPO_{4}^{2 -} + H^{+} \to H_{2} PO_{4}^{-}$
  
  Answer: B
  2 marks · Identify conjugate acid-base pairs
4. Question 5.6 · May/June 2025 · Paper 2 · National (DBE) · 2 marks
The reaction between magnesium carbonate pellets, $MgCO_{3}$ (s), and EXCESS dilute hydrochloric acid, HCℓ(aq), is used to investigate the effect of concentration on the rate of a reaction.

$MgCO_{3} (s) + 2 HC ℓ (aq) \to MgC ℓ_{2} (aq) + H_{2} O (ℓ) + CO_{2} (g)$

The apparatus used for this investigation is shown below.
5.6 How will the final mass of $CO_{2}$ (g) produced in EXPERIMENT 2 compare to that of EXPERIMENT 3? Choose from MORE THAN, LESS THAN or THE SAME.

Give a reason for the answer.(2)
Show the memo (2 ticks)Memo
1. ✓
  ComparisonThe same
  1 mark · Identify the limiting reagent
2. ✓
  ReasonThe same amount $MgCO_{3}$ is used in each experiment.
  1 mark · Identify the limiting reagent
5. Question 1 · Siyavula Grade 11 Physical Sciences, 12.3 Activation energy and the activated complex, Worked example 1 · 2 marks
Refer to the graph of potential energy against time for a reaction and then answer the questions that follow.
1 Calculate $Δ H$ .(2)
Show the memo (2 ticks)Memo
1. ✓
  Formula and values $Δ H = energy of products - energy of reactants$
  $= 10 kJ - 45 kJ$
  1 mark · Interpret the energy change of reactions
2. ✓
  Answer $Δ H = - 35$ kJ
  1 mark · Interpret the energy change of reactions

Chemical Change Grade 11 videos

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

Conservation Of Mass Grade 10Kevinmathscience

Stoichiometry: Mole Ratios | Grade 10, 11 and 12 ChemistryMiss Martins Maths and Science

The mole concept: What is a mole? Quantitative aspects of chemical changeMiss Martins Maths and Science

How to calculate moles using mass | Stoichiometry grade 10, 11 and 12Miss Martins Maths and Science

Concentration of solutions ChemistryMiss Martins Maths and Science

Empirical Formula: How to calculate | Stoichiometry | ChemistryMiss Martins Maths and Science

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