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Quiz Chapter 7: Rate of Reaction

10 questions · Form 4 Chemistry Bab 7: Rate of Reaction

Question 1 of 10Score: 0

How is the instantaneous rate of reaction determined from a gas-volume-against-time graph?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. How is the instantaneous rate of reaction determined from a gas-volume-against-time graph?

  1. By dividing the final volume by total time taken
  2. By taking the average of initial and final rates
  3. By finding the area under the graph at time t
  4. By calculating the gradient of the tangent to the curve at time t
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Answer: D

The instantaneous rate of reaction at time t is calculated from the gradient of the tangent drawn at that exact point on the curve.

2. Which factor explains why storing food in a refrigerator slows down spoilage?

  1. Higher pressure inside the refrigerator
  2. Lower temperature reduces bacterial metabolic reaction rates
  3. Reduced total surface area of food items
  4. Removal of catalysts present in food
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Answer: B

Lower temperatures reduce the kinetic energy of molecules, slowing down biological and chemical decay reactions.

3. What happens to the mass of a catalyst at the end of a chemical reaction?

  1. It doubles
  2. It decreases by half
  3. It drops to zero
  4. It remains unchanged
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Answer: D

A catalyst increases reaction speed without undergoing any permanent chemical or quantitative mass change.

4. Which catalyst is used in the decomposition of hydrogen peroxide to produce oxygen gas in laboratory demonstrations?

  1. Manganese(IV) oxide
  2. Iron filings
  3. Phosphoric acid
  4. Aluminium oxide
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Answer: A

Manganese(IV) oxide (MnO2) acts as a catalyst to speed up the decomposition of H2O2 into H2O and O2 gas.

5. In a curve showing gas volume against time, what does a horizontal flat line indicate?

  1. The rate of reaction is at its maximum
  2. The reaction has completed because at least one reactant is fully used up
  3. The catalyst has been exhausted
  4. The activation energy has increased to infinity
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Answer: B

A horizontal flat gradient indicates that gas production has ceased because the limiting reactant is completely consumed.

6. Why do powdered marble chips (CaCO3) react faster with hydrochloric acid than marble lumps of the same mass?

  1. Powdered marble has lower activation energy
  2. Powdered marble increases the kinetic energy of acid molecules
  3. Powdered marble provides a larger total surface area exposed to collision
  4. Powdered marble increases the concentration of the acid solution
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Answer: C

Smaller particle size provides a larger total surface area exposed to reactant collisions, increasing collision frequency.

7. What happens to the particles when the temperature of a reaction mixture increases?

  1. Activation energy decreases significantly
  2. Their average kinetic energy increases, leading to more frequent effective collisions
  3. The overall enthalpy change of the reaction becomes positive
  4. The orientation of particle collisions is no longer required
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Answer: B

Higher temperature increases kinetic energy, causing particles to move faster and collide more frequently with energy >= Ea.

8. What is the catalyst used in the Haber Process for manufacturing ammonia?

  1. Platinum
  2. Iron
  3. Vanadium(V) oxide
  4. Manganese(IV) oxide
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Answer: B

Finely divided iron (Fe) acts as the catalyst to speed up the synthesis of ammonia in the Haber Process.

9. How does doubling the concentration of hydrochloric acid affect its reaction rate with magnesium ribbon?

  1. Decreases collision frequency per unit volume
  2. Increases the number of hydrogen ions per unit volume, raising effective collision frequency
  3. Lowers the activation energy of the reaction
  4. Increases the mass of magnesium consumed per second without changing collision rate
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Answer: B

Higher concentration increases particle count per unit volume, directly increasing total and effective collision frequencies.

10. If 50 cm³ of carbon dioxide gas is collected in 20 seconds, what is the average rate of reaction?

  1. 2.5 cm³/s
  2. 0.4 cm³/s
  3. 1000 cm³/s
  4. 10.0 cm³/s
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Answer: A

Average rate = Total volume / Total time = 50 cm³ / 20 s = 2.5 cm³/s.

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