CIE iGCSE Co-Ordinated Science C6.2 Rate of reaction Exam Style Questions Paper 2
▶️ Answer/Explanation
Heating increases the kinetic energy of particles, causing them to move faster. This results in more frequent collisions between reactant particles (statement 1). Additionally, a greater proportion of collisions have sufficient energy to exceed the activation energy, meaning more collisions are successful (statement 2). Statement 3 is incorrect because gas pressure increase is an effect of heating, not a reason for the rate increase. Statement 4 is incorrect because activation energy is a constant for a given reaction and does not change with temperature (only a catalyst can lower activation energy). Therefore, statements 1 and 2 correctly explain the observation.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
For the same number of successful collisions per second to occur, an increase in temperature (which increases collision frequency and energy) can be balanced by a decrease in reactant concentration (which reduces the number of particles available to collide). This way, the overall rate of successful collisions remains unchanged. Increasing temperature while keeping concentration unchanged would increase the rate, while decreasing both would decrease it further.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Both “per unit time” methods require the measurement to be tracked against time, so a stop-clock is always needed to time the readings.
A gas syringe is only needed for the gas volume method, and a balance is only needed for the mass-loss method.
A thermometer is not required for either method, since neither tracks temperature.
✅ Answer: (C)
A gas syringe is only needed for the gas volume method, and a balance is only needed for the mass-loss method.
A thermometer is not required for either method, since neither tracks temperature.
✅ Answer: (C)
▶️ Answer/Explanation
The Contact process actually uses a vanadium(V) oxide catalyst, not nickel, so statement 1 is incorrect.
A pressure of about 1–2 atmospheres and a temperature of about 450 °C are the correct standard conditions used, so statements 2 and 3 are correct.
This makes the combination of statements 2 and 3 the accurate description of the conditions.
✅ Answer: (D)
A pressure of about 1–2 atmospheres and a temperature of about 450 °C are the correct standard conditions used, so statements 2 and 3 are correct.
This makes the combination of statements 2 and 3 the accurate description of the conditions.
✅ Answer: (D)
▶️ Answer/Explanation
Using larger pieces of a solid reactant reduces the exposed surface area for a given mass.
A smaller surface area means fewer particles are available for collisions, decreasing collision frequency and reaction rate.
All the other options increase collision frequency by increasing particle concentration or energy.
✅ Answer: (D)
A smaller surface area means fewer particles are available for collisions, decreasing collision frequency and reaction rate.
All the other options increase collision frequency by increasing particle concentration or energy.
✅ Answer: (D)