Factors affecting rate - temperature, concentration, surface, area and catalysts — Free MYP5 Chemistry Practice Questions

1QuestionCatalysts and lowering activation energyConcept Practice

2 marks~3 minCriterion A

The reaction profile diagram below shows two curves, A and B, for the same chemical reaction. Curve A has a higher energy peak than Curve B. The energy difference between the reactants and the peak of Curve A is labelled $X$.

a

Deduce which curve, A or B, represents the catalysed reaction. [1]

b

Explain how a catalyst enables more reactant molecules to form products, with reference to the energy labelled $X$. [1]

Solutions

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2QuestionSurface area and its role in solid reactionsAssessment Practice

2 marks~3 minCriterion D

In the Haber process, iron is used as a catalyst to produce ammonia ($\text{NH}_3$) from nitrogen and hydrogen gases. A factory switches from iron pellets to powdered iron.

a

Explain why powdered iron increases the rate of reaction compared to iron pellets. [1]

b

A faster reaction allows the factory to maintain the same ammonia output at a lower operating temperature. Evaluate one environmental consequence of this temperature reduction. [1]

Solutions

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3QuestionInterpreting rate graphs and experimental dataAssessment Practice

5 marks~8 minCriterion C

A student proposes the hypothesis: "Increasing the temperature of a chemical reaction always doubles the reaction rate." To investigate this, they measure the time for a fixed mass of solid calcium carbonate (CaCO3) and 50 cm³ of 1.0 mol dm⁻³ hydrochloric acid (HCl) to fully react at four temperatures.

Temperature (°C)	20	30	40	50
Reaction time (s)	120	60	30	15

a

Calculate the reaction rate at each temperature using rate $\propto \dfrac{1}{\text{time}}$. Show your working. [2]

b

Using your calculated rates, explain whether the data supports the hypothesis for a 10°C temperature increase. [1]

c

Evaluate the student's hypothesis as a general claim, using collision theory to justify why it is an oversimplification. [2]

Solutions

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4QuestionEffect of temperature on particle energy and collisionsAssessment Practice

6 marks~9 minCriterion B

A student investigates how temperature affects the rate of reaction between sodium thiosulfate solution and hydrochloric acid. A sulfur precipitate forms, making the solution turn cloudy. The student records the time for the solution to become fully opaque at five temperatures.

Temperature (°C)	20	30	40	50	60
Time (s)	120	60	30	15	7.5

a

Construct a graph of time (y-axis, 0–140 s) against temperature (x-axis, 20–70°C), plot all five points, and describe the pattern shown. [2]

b

Explain, using collision theory, why increasing temperature increases the rate of this reaction. [2]

c

A second student claims the reaction time at 70°C will be approximately 3.75 s. Evaluate this claim by analysing the pattern in the data and linking it to the behaviour of particles at higher temperatures. [2]

Solutions

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Questions 5-84

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