Factors affecting rate - temperature, concentration, surface, area and catalysts — Free MYP4 Chemistry Practice Questions

1QuestionSurface area and its role in solid reactionsConcept Practice

3 marks~5 minCriterion A

A student adds a large marble chip of calcium carbonate ($CaCO_3(s)$) to a beaker of dilute hydrochloric acid ($HCl(aq)$). In a separate beaker, the same mass of powdered calcium carbonate is added to an equal volume and concentration of hydrochloric acid. The powdered form reacts significantly faster.

a

Construct the balanced chemical equation, including state symbols, for the reaction between calcium carbonate and hydrochloric acid. [1]

b

Explain, using collision theory, why the powdered calcium carbonate reacts faster than the marble chip. [2]

Solutions

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2QuestionEffect of temperature on particle energy and collisionsAssessment Practice

5 marks~8 minCriterion C

A student investigates the effect of temperature on the reaction between sodium thiosulfate solution and hydrochloric acid, measuring the time for the solution to turn opaque.

Temperature (°C)	10	20	30	40	50
Reaction time (s)	120	60	30	15	7.5
Mean kinetic energy (kJ mol$^{-1}$)	3.5	3.6	3.7	3.8	3.9

The student hypothesises: "The reaction rate doubles every 10°C because particles move twice as fast."

a

Calculate the reaction rate at 10°C and at 50°C, and deduce the overall rate increase across this temperature range. [1]

b

Using the kinetic energy data, show that particle speed does not double between 10°C and 20°C, given that $KE \propto v^2$. [2]

c

Evaluate the student's hypothesis, explaining the actual cause of the observed rate increase using collision theory and the Maxwell-Boltzmann distribution. [2]

Solutions

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3QuestionEffect of temperature on particle energy and collisionsAssessment Practice

6 marks~9 minCriterion D

Food spoilage is accelerated by microbial and enzymatic activity. Refrigerators typically maintain an internal temperature of around 4 °C, compared with a room temperature of approximately 22 °C.

a

Explain how lowering the temperature from 22 °C to 4 °C reduces the rate of food spoilage reactions, with reference to particle energy and collision frequency. [2]

b

Analyse the health risks that arise when perishable food is left at room temperature for several hours, linking your answer to reaction rate principles. [2]

c

Evaluate the limitations of refrigeration as a universal food preservation strategy, considering at least two distinct factors. [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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