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CHEMISTRY, M3 EQ-Bank 16

Describe how activation energy, collision frequency, and molecular orientation work together to determine the rate of a chemical reaction. In your answer, define what each term refers to and relate these factors to collision theory.   (5 marks)

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  • Activation Energy: For a reaction to occur, the colliding molecules must have enough energy to overcome the activation energy barrier, which is the minimum energy required to break the bonds in the reactants and initiate the reaction. 
  • Collision Frequency: The rate of a reaction is also influenced by how frequently reactant molecules collide.
  • Molecular Orientation: In addition to having enough energy, molecules must collide with the correct orientation for a reaction to take place. Reactant molecules need to align in a way that allows bonds to break and new bonds to form. 
  • Increasing collision frequency increases the number of opportunities for molecules to collide, but only those collisions with enough energy and the correct orientation will lead to successful bond rearrangements.
  • For the maximum rate of reaction there needs to be a lower activation energy which makes it easier for collisions to result in a reaction, the proper orientation that ensures when collisions occur, they lead to the formation of products and a high collision frequency.
Show Worked Solution
  • Activation Energy: For a reaction to occur, the colliding molecules must have enough energy to overcome the activation energy barrier, which is the minimum energy required to break the bonds in the reactants and initiate the reaction. 
  • Collision Frequency: The rate of a reaction is also influenced by how frequently reactant molecules collide.
  • Molecular Orientation: In addition to having enough energy, molecules must collide with the correct orientation for a reaction to take place. Reactant molecules need to align in a way that allows bonds to break and new bonds to form. 
  • Increasing collision frequency increases the number of opportunities for molecules to collide, but only those collisions with enough energy and the correct orientation will lead to successful bond rearrangements.
  • For the maximum rate of reaction there needs to be a lower activation energy which makes it easier for collisions to result in a reaction, the proper orientation that ensures when collisions occur, they lead to the formation of products and a high collision frequency.

CHEMISTRY, M3 EQ-Bank 8 MC

Which statement best explains how molecular orientation affects the rate of a chemical reaction according to collision theory?

  1. Reactant molecules must collide with enough energy, but the orientation of the molecules is irrelevant.
  2. Correct orientation only affects reactions that involve more than two reactant molecules.
  3. Incorrect molecular orientation increases the activation energy required for the reaction to proceed.
  4. Even with sufficient energy, reactants must collide in the correct orientation to allow bonds to break and form.
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\(D\)

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  • For a reaction to occur, not only must reactants collide with sufficient energy, but they must also collide in the correct orientation to break existing bonds and form new ones.
  • Even if the reactants have enough energy, incorrect orientation can prevent a successful reaction.

\(\Rightarrow D\)

CHEMISTRY, M3 EQ-Bank 3 MC

When molecules react, the final rate of a chemical reaction is determined by which of the following factors?

  1. The proportion of collisions where the number of molecules are keep the same.
  2. The proportion of collisions where molecules have the correct orientation
  3. The proportion of collisions where atoms are destroyed
  4. The proportion of collisions where molecules form larger structures
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\(B\)

Show Worked Solution
  • For a reaction to occur, it is not enough for molecules to simply collide.
  • They must collide with the correct orientation for bonds to break and new ones to form. Even if the energy is sufficient, an incorrect orientation will not result in a successful reaction.
  • Therefore, the rate of a chemical reaction is largely determined by the proportion collisions that occur with the proper orientation between reacting molecules.

\(\Rightarrow B\)