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CAIE A-Level Chemistry AS 8.1 Rate of Reaction Questions

Practise calculating reaction rates from tables and graphs, then explaining changes using concentration, pressure and collisions.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • calculate average rate from gas volume, concentration change or moles over time
  • explain rate changes using collision frequency and effective collisions
  • interpret rate graphs or tables to compare early and late stages of a reaction

Covered syllabus points

8.1.1—Terms: rate of reaction, frequency of collisions8.1.2—8.1.3—Experimental data to calculate the rate

Question 1

[Maximum number: 1]

A student carries out four experiments to investigate the rate of reaction between 3.0 g of calcium carbonate and hydrochloric acid.

CaCO3( s)+2HCl(aq)→CaCl2(aq)+CO2( g)+H2O(l)\mathrm{CaCO}_{3}(\mathrm{~s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

experiment 1CaCO31 \quad \mathrm{CaCO}_{3} powder +2.0moldm−3HCl+2.0 \mathrm{moldm}^{-3} \mathrm{HCl} at 35∘C35^{\circ} \mathrm{C}
experiment 2CaCO32 \mathrm{CaCO}_{3} powder +2.0moldm−3HCl+2.0 \mathrm{moldm}^{-3} \mathrm{HCl} at 35∘C35^{\circ} \mathrm{C}
experiment 3 large chips of CaCO3+1.0moldm−3HCl\mathrm{CaCO}_{3}+1.0 \mathrm{moldm}^{-3} \mathrm{HCl} at room temperature
experiment 4 large chips of CaCO3+1.0moldm−3HCl\mathrm{CaCO}_{3}+1.0 \mathrm{moldm}^{-3} \mathrm{HCl} at 35∘C35^{\circ} \mathrm{C}

The student collects the CO2( g)\mathrm{CO}_{2}(\mathrm{~g}) and times how long it takes to produce the same volume of gas for each experiment.

What could be the correct times for the four experiments?

experiment 1 /s

experiment 2 /s

experiment 3 /s

experiment 4 /s

5

10

30

95

5

10

95

30

5

30

95

10

95

30

10

5

Question 2

[Maximum number: 1]

The decomposition of hydrogen peroxide in the presence of MnO2\mathrm{MnO}_{2} produces water and oxygen gas.

The volume of gas collected when 0.2 g of MnO2\mathrm{MnO}_{2} is added to two different hydrogen peroxide solutions at 20∘C20^{\circ} \mathrm{C} is shown on the graph as curves X and Y .

Figure for Question 2 — CAIE A-Level Chemistry AS

Which row shows the conditions that will result in curves X and Y ?

volume of H2O2/cm3\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{cm}^{3}

concentration of H2O2/moldm−3\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{moldm}^{-3}

form of MnO2\mathrm{MnO}_{2}

volume of H2O2/cm3\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{cm}^{3}

concentration of H2O2/moldm−3\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{moldm}^{-3}

form of MnO2\mathrm{MnO}_{2}

50

0.1

lumps

50

0.2

powder

25

0.2

powder

25

0.1

lumps

50

0.1

lumps

20

0.2

powder

20

0.2

powder

40

0.1

lumps

Question 3

[Maximum number: 1]

The factors affecting the rate of reaction between aqueous sodium thiosulfate and hydrochloric acid can be investigated. The ionic equation for the reaction is shown.

S2O32−(aq)+2H+(aq)→H2O(l)+S( s)+SO2(aq)\mathrm{S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq})+2 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{S}(\mathrm{~s})+\mathrm{SO}_{2}(\mathrm{aq})

Which of the following can be used to investigate the rate of this reaction?
1 change of mass
2 change of appearance caused by formation of a precipitate
3 change of electrical conductivity

A

1, 2 and 3 are correct

B

1 and 2 only are correct

C

2 and 3 only are correct

D

1 only is correct

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