Questions on Collision Theory
Multiple-Choice Questions: Collision Theory
1. According to collision theory, what must happen for a chemical reaction to occur?
A) Reactants must be in solid state
B) Reactants must be at the same temperature
C) Reactants must collide with sufficient energy and proper orientation
D) Products must have lower energy than reactants
E) Reactants must be in aqueous solution
2. What does the term "activation energy" refer to in collision theory?
A) The energy required to cool the system
B) The average kinetic energy of molecules
C) The energy needed to form a stable product
D) The minimum energy needed for an effective collision
E) The energy released in an exothermic reaction
3. Which factor does not increase the frequency of collisions between molecules?
A) Increasing concentration
B) Increasing pressure (for gases)
C) Increasing temperature
D) Adding a catalyst
E) Increasing surface area
4. In collision theory, what is meant by an "effective collision"?
A) A collision that results in energy loss
B) A collision that forms an intermediate
C) A collision that leads to a successful reaction
D) A collision with any two molecules
E) A collision in a non-polar solvent
5. Why does increasing the temperature increase the rate of reaction according to collision theory?
A) It decreases the activation energy
B) It increases molecular mass
C) It increases the number of effective collisions
D) It makes collisions less frequent
E) It changes the enthalpy of the system
6. Which statement is true according to collision theory?
A) All collisions lead to a reaction
B) Higher energy always results in a faster reaction
C) Only collisions with correct orientation and sufficient energy lead to reaction
D) Effective collisions must occur in a liquid phase
E) Reactions cannot occur at low temperatures
7. What role does orientation of molecules play in reaction rate according to collision theory?
A) It determines the product concentration
B) It is irrelevant as long as energy is sufficient
C) Correct orientation increases the chance of an effective collision
D) It only matters in heterogeneous reactions
E) Orientation affects the pH of the reaction medium
8. Which of the following changes does not support more effective collisions?
A) Increasing the surface area of a solid reactant
B) Using a catalyst
C) Lowering the temperature
D) Increasing pressure for gaseous reactants
E) Increasing reactant concentration
9. In a gaseous reaction, why does increasing pressure generally increase the rate of reaction?
A) It reduces molecular size
B) It decreases activation energy
C) It increases the frequency of collisions
D) It increases entropy
E) It removes side products
10. What does collision theory say about ineffective collisions?
A) They form by-products
B) They result in heat absorption
C) They occur with insufficient energy or improper orientation
D) They occur only in catalysts
E) They increase the activation energy
11. What is the effect of a catalyst according to collision theory?
A) It increases the number of particles
B) It increases the activation energy
C) It provides an alternative pathway with lower activation energy
D) It decreases the enthalpy change
E) It increases the temperature
12. Which statement best explains why powdered solids react faster than large chunks?
A) They have more energy
B) They have less volume
C) They dissolve more easily
D) They offer greater surface area for collisions
E) They are less dense
13. Which of the following best describes the energy distribution among molecules in a reaction mixture?
A) All molecules have the same energy
B) Most molecules have zero energy
C) Only a few have enough energy to react
D) All molecules are below activation energy
E) Energy increases linearly with time
14. Which diagram best represents energy changes in collision theory?
A) Reaction coordinate diagrams
B) Phase diagrams
C) Titration curves
D) Heating curves
E) Equilibrium graphs
15. How does temperature affect the fraction of molecules with energy equal to or greater than activation energy?
A) It has no effect
B) It decreases the fraction
C) It keeps the fraction constant
D) It increases the fraction
E) It eliminates activation energy
16. What is the significance of the Maxwell-Boltzmann distribution in collision theory?
A) It measures pH changes
B) It shows the concentration of reactants
C) It describes the energy distribution among molecules
D) It calculates reaction yield
E) It predicts product formation
17. What happens to the number of effective collisions when temperature increases?
A) It remains the same
B) It decreases
C) It increases
D) It decreases only for endothermic reactions
E) It fluctuates randomly
18. Why is activation energy considered a barrier in collision theory?
A) It prevents products from forming too quickly
B) It ensures equilibrium is reached
C) It must be overcome for a successful reaction to occur
D) It keeps temperature constant
E) It slows the reverse reaction
19. Which of the following is not a postulate of collision theory?
A) Particles must collide to react
B) Collisions must have sufficient energy
C) Particles must be in a gaseous state
D) Proper orientation is required for reaction
E) Most collisions are ineffective
20. Which factor affects both frequency and effectiveness of collisions?
A) Enthalpy change
B) Temperature
C) Reaction volume
D) Equilibrium constant
E) Solubility
Answer Key with Explanations
1. C – A reaction needs collisions with enough energy and proper orientation.
2. D – Activation energy is the minimum energy needed for a reaction to occur.
3. D – A catalyst does not increase collision frequency, but it lowers activation energy.
4. C – An effective collision results in a successful chemical reaction.
5. C – Higher temperature increases the kinetic energy, leading to more effective collisions.
6. C – Both correct energy and orientation are required for a successful collision.
7. C – Proper molecular alignment is key to forming new bonds.
8. C – Lower temperature reduces the energy and slows reactions.
9. C – Higher pressure leads to more frequent collisions in gases.
10. C – Collisions with insufficient energy or wrong orientation don’t result in reaction.
11. C – Catalysts offer an alternative route with lower activation energy.
12. D – Greater surface area allows more frequent contact between reactants.
13. C – Only a small fraction of molecules naturally have enough energy to react.
14. A – Reaction coordinate diagrams show activation energy and energy profiles.
15. D – Temperature increases the number of molecules that can overcome the activation energy.
16. C – Maxwell-Boltzmann distribution shows how molecular energies are spread out.
17. C – More molecules have sufficient energy at higher temperatures.
18. C – Activation energy must be overcome to allow a reaction to proceed.
19. C – Collision theory applies in all phases, not just gases.
20. B – Temperature increases energy (affecting effectiveness) and motion (affecting frequency).
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