Questions on Activation Energy
Multiple-Choice Questions: Activation Energy
1. What is activation energy?
A) The total energy of the products
B) The energy released during a reaction
C) The energy required to reach equilibrium
D) The minimum energy required for a reaction to occur
E) The heat capacity of the system
2. What happens when particles collide with less energy than the activation energy?
A) They always form products
B) They bounce off each other without reacting
C) They lose mass
D) They become radioactive
E) They combine temporarily and remain stable
3. Which factor most directly affects the value of activation energy?
A) Pressure
B) Concentration
C) Temperature
D) Type of chemical bonds in the reactants
E) Volume of the reaction container
4. In a reaction profile, what does the peak of the curve represent?
A) The energy of the products
B) The energy of the reactants
C) The activation energy
D) The energy of the transition state
E) The equilibrium point
5. What is the transition state in a chemical reaction?
A) The stable intermediate compound
B) The reactants in their original state
C) The final product
D) The high-energy, unstable state during a reaction
E) The average energy of reactants and products
6. Which of the following statements is true about activation energy?
A) It is always negative
B) It is not needed in exothermic reactions
C) It determines whether a collision leads to a reaction
D) It depends only on pressure
E) It decreases as concentration increases
7. Which graph would best show the effect of temperature on activation energy?
A) pH vs. time
B) Rate vs. pressure
C) Temperature vs. reaction time
D) ln(k) vs. 1/T (Arrhenius plot)
E) Concentration vs. volume
8. How does a catalyst affect the activation energy of a reaction?
A) It increases it
B) It decreases it
C) It removes it completely
D) It does not affect it
E) It makes it unpredictable
9. Which of the following is not a method for lowering activation energy?
A) Using a catalyst
B) Increasing temperature
C) Using enzymes (biological catalysts)
D) Using an alternative reaction pathway
E) Designing a surface catalyst
10. Why does increasing temperature increase the rate of reaction with respect to activation energy?
A) More molecules have energy equal to or greater than the activation energy
B) It increases the mass of the molecules
C) It eliminates the need for activation energy
D) It raises the activation energy
E) It breaks the catalyst bonds
11. What is the typical unit of activation energy in the SI system?
A) J/mol
B) atm
C) L·mol⁻¹
D) K
E) mol/s
12. Which reaction would have the lowest activation energy?
A) A slow combustion reaction
B) A spontaneous redox reaction
C) A nuclear reaction
D) A reaction requiring a catalyst
E) A reaction in equilibrium
13. If a reaction has a high activation energy, it is likely to:
A) Proceed quickly at room temperature
B) Be unaffected by temperature changes
C) Require a catalyst to proceed efficiently
D) Occur spontaneously without energy input
E) Have no intermediate steps
14. Which of the following is correct regarding activation energy and endothermic reactions?
A) Activation energy is zero for endothermic reactions
B) All endothermic reactions have no transition state
C) Activation energy is only required in exothermic reactions
D) Endothermic reactions still require activation energy
E) Activation energy equals enthalpy change
15. In the Arrhenius equation, what does Ea represent?
A) Enthalpy of reaction
B) Average kinetic energy
C) Activation energy
D) Atomic radius
E) Number of moles
16. Why do some reactions with high activation energy occur slowly even if they are thermodynamically favorable?
A) The products are unstable
B) The temperature is always too high
C) Most collisions don't have enough energy to overcome the barrier
D) The system is at equilibrium
E) The entropy is too high
17. Which statement best explains the role of activation energy in collision theory?
A) It increases the product concentration
B) It ensures that reactions go to completion
C) It determines whether collisions result in reaction
D) It reduces the molecular motion
E) It increases the solubility of reactants
18. How does activation energy relate to reaction rate?
A) Higher Ea always means faster reaction
B) Lower Ea leads to faster reaction
C) Activation energy has no effect on rate
D) Only temperature affects rate
E) Ea only applies to heterogeneous reactions
19. What is the effect of a catalyst on the transition state?
A) It eliminates the transition state
B) It raises its energy
C) It lowers its energy, making it easier to reach
D) It replaces it with an intermediate
E) It reverses the reaction
20. If two reactions occur at the same temperature, but one has a lower activation energy, what will likely happen?
A) Both reactions proceed at the same rate
B) The one with higher activation energy proceeds faster
C) The one with lower activation energy proceeds faster
D) Neither reaction occurs
E) Both reactions produce the same product
Answer Key with Explanations
1. D – Activation energy is the minimum energy required for a reaction to proceed.
2. B – Without enough energy, collisions do not result in reactions.
3. D – Bond types and strengths determine how much energy is needed to break them.
4. D – The peak of the reaction profile represents the high-energy transition state.
5. D – The transition state is the temporary, unstable arrangement of atoms.
6. C – A collision must overcome activation energy to be successful.
7. D – The Arrhenius plot (ln(k) vs. 1/T) helps determine activation energy.
8. B – Catalysts lower the activation energy.
9. B – Temperature increases kinetic energy but does not reduce Ea itself.
10. A – Higher temperature means more particles can overcome Ea.
11. A – Joules per mole is the standard unit of activation energy.
12. D – Catalysts reduce activation energy, making reactions proceed faster.
13. C – A high Ea often needs a catalyst to speed up the reaction.
14. D – Both endothermic and exothermic reactions require activation energy.
15. C – Ea stands for activation energy in the Arrhenius equation.
16. C – Even if products are favored, the energy barrier can prevent fast reaction.
17. C – Only collisions with enough energy to overcome Ea are effective.
18. B – Lower activation energy results in a faster rate.
19. C – Catalysts lower the energy of the transition state.
20. C – Lower activation energy means more particles can react, so it's faster.
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