Activation energy Knowledge-Based Practice

Questions

1. 1.

   Why is an initial investment of activation energy required even for exergonic reactions that release free energy overall?

   • A) An initial energy input is necessary to shift the chemical equilibrium toward the reactants.
   • B) The net change in free energy must be converted from negative to positive before products can form.
   • C) Chemical bonds within the reactant molecules must be destabilized and strained before new bonds can form.
   • D) Energy must be absorbed to raise the final ground-state energy of the products above that of the reactants.
2. 2.

   How does the magnitude of the activation energy barrier directly influence the rate of a chemical reaction at a constant physiological temperature?

   • A) A higher activation energy barrier results in a slower reaction rate because fewer reactant molecules possess sufficient kinetic energy to overcome it.
   • B) A higher activation energy barrier results in a faster reaction rate because reactant molecules collide with greater overall frequency.
   • C) A lower activation energy barrier causes the reaction to become endergonic because it reduces the net free energy change.
   • D) The magnitude of the activation energy has no effect on reaction rate because reaction velocity is determined solely by substrate concentration.
3. 3.

   Which of the following properties of a chemical reaction remains completely unchanged regardless of the magnitude of its activation energy?

   • A) The net change in free energy ($\Delta G$) between the initial reactants and final products
   • B) The overall rate at which reactants are converted into products
   • C) The proportion of reactant molecules possessing sufficient kinetic energy to react
   • D) The energy level required to reach the transition state
4. 4.

   What does the activation energy of a chemical reaction represent at the molecular level?

   • A) The net amount of free energy released when products are formed from reactants
   • B) The total thermal energy possessed by all reactant molecules in a solution
   • C) The minimum energy required to contort reactant molecules into an unstable transition state
   • D) The energy difference that determines whether a reaction is endergonic or exergonic
5. 5.

   Which of the following statements correctly describes how an enzyme influences the activation energy of a biochemical reaction?

   • A) It lowers the activation energy required to reach the transition state without altering the net free energy change of the reaction.
   • B) It increases the activation energy to make the transition state more stable and release more total energy.
   • C) It eliminates the need for activation energy completely by supplying thermal energy to the reactants.
   • D) It alters the net free energy change of the reaction while keeping the activation energy barrier constant.

Answers and step-by-step solutions appear after you finish the test.