Grade 12 Physical Sciences · Chemical Change

Interpret reaction rate graphs

Read reaction rate graphs to see when a reaction is fastest or stops, or sketch the curve for new conditions such as a higher temperature.

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Rate of Reaction Graphs Grade 12 ChemistryMiss Martins Maths and Science

How to explain rate of reaction graphsChemJungle

GCSE Chemistry - Rates of Reaction - How to Measure it | How to Show it on Graphs (2027/28 exams)Cognito

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Question 1.4 · May/June 2024 · Paper 2 · National (DBE) · 2 marks

1.4 In an experiment 5 g of calcium carbonate,

CaCO_{3}

(s), reacts with EXCESS hydrochloric acid, HCℓ(aq), at a temperature of

40

°C.

CaCO_{3} (s) + 2 HC ℓ (aq) \to CaC ℓ_{2} (aq) + H_{2} O (ℓ) + CO_{2} (g)

The volume of

CO_{2}

(g) produced versus time is shown by CURVE P in the graph below.

The experiment is repeated with 10 g of the same

CaCO_{3}

(s) sample and an excess of HCℓ(aq) with the same concentration at

40

°C. Which ONE of the curves will now be obtained?(2) Diagram for question 1.4

A Curve I
B Curve II
C Curve III
D Curve IV

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More past paper questions: interpret reaction rate graphs

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3. Question 5.1.4 · November 2024 · Paper 2 · National (DBE) · 2 marks
5.1 The reaction between pure aluminium, Aℓ(s), and EXCESS hydrochloric acid, HCℓ(aq), is used to investigate the factors that affect the rate of a reaction.

The balanced equation for the reaction is:

$2 A ℓ (s) + 6 HC ℓ (aq) \to 2 A ℓ C ℓ_{3} (aq) + 3 H_{2} (g)$

Answer the questions that follow.
EXPERIMENT II

Experiment I is repeated using a $2$ mol·dm $^{- 3}$ HCℓ solution.
5.1.4 Redraw the above graph (NO numerical values need to be shown) in your ANSWER BOOK and label the curve A. On the same set of axes, draw the curve that will be obtained for Experiment II. Label this as curve B.(2)
Show the memo (2 ticks)Memo
1. ✓
  Curve B starts at origin and ends at the same point as curve ACurve B starts at the origin and levels off at the same final volume of $H_{2}$ as curve A.
  1 mark · Interpret reaction rate graphs
2. ✓
  Gradient of curve B steeper for the whole durationCurve B is steeper than curve A for the whole duration (it reaches the final volume sooner).
  1 mark · Interpret reaction rate graphs
4. Question 5.2.1 · November 2025 · Paper 2 · National (DBE) · 1 mark
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.
5.2.1 At which time, 10 s or 30 s, is the reaction rate higher?(1)
Show the memo (1 tick)Memo
1. ✓
  Time of higher rate10 (s)
  1 mark · Interpret reaction rate graphs
5. Question 5.3 · May/June 2025 · Paper 2 · National (DBE) · 1 mark
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.
Three experiments using different concentrations of HCℓ(aq) are carried out. The concentration of the HCℓ(aq) during each experiment does not change.

The INCOMPLETE graph of the results of the experiments is shown below.
5.3 Give a reason why the mass of the reaction mixture and flask decreases.(1)
Show the memo (1 tick)Memo
1. ✓
  Reason for mass decrease $CO_{2}$ /gas escapes from the reaction flask.
  1 mark · Interpret reaction rate graphs
6. Question 5.1 · May/June 2023 · Paper 2 · National (DBE) · 1 mark
Consider the following decomposition reaction that takes place in a sealed $2$ dm $^{3}$ container:

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

The graph below shows how the concentrations of $N_{2} O_{5}$ (g) and $NO_{2}$ (g) change with time.
5.1 Refer to the graph above and give a reason why curve A represents the change in the concentration of $NO_{2}$ (g).(1)
Show the memo (1 tick)Memo
1. ✓
  Reason from the graphInitial concentration is 0 (of $NO_{2}$ ). / Concentration increases. / Curve starts at 0.
  1 mark · Interpret reaction rate graphs

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