Activation energy and the Arrhenius equation Knowledge-Based Download PDF

Questions

1. 1.

   How does the addition of a catalyst at constant temperature affect the activation energy ($E_a$) and the rate constant ($k$) of a chemical reaction?

   • A) It increases $E_a$ and decreases $k$.
   • B) It increases $E_a$ and increases $k$.
   • C) It decreases $E_a$ and decreases $k$.
   • D) It decreases $E_a$ and increases $k$.
2. 2.

   In the Arrhenius equation, $k = A e^{-E_a/(RT)}$, what physical characteristics of reacting molecules are primarily accounted for by the pre-exponential factor ($A$)?

   • A) The average kinetic energy and the minimum energy threshold needed for bond breaking
   • B) The total frequency of collisions and the probability of proper molecular orientation
   • C) The fraction of molecular collisions possessing kinetic energy greater than or equal to $E_a$
   • D) The net enthalpy change and thermodynamic driving force of the overall reaction
3. 3.

   In the Arrhenius equation, $k = A e^{-E_a/(RT)}$, what does the exponential term $e^{-E_a/(RT)}$ physically represent?

   • A) The total frequency of collisions occurring between reactant molecules per unit volume
   • B) The fraction of molecular collisions that have kinetic energy equal to or greater than the activation energy
   • C) The probability that colliding molecules possess the correct spatial orientation for reaction
   • D) The ratio of the forward activation energy to the reverse activation energy of the reaction
4. 4.

   According to the linear form of the Arrhenius equation, a plot of $\ln k$ versus $1/T$ for a chemical reaction yields a straight line. What is the mathematical expression for the slope of this line?

   • A) $-\frac{R}{E_a}$
   • B) $-\frac{E_a}{R}$
   • C) $\frac{E_a}{R}$
   • D) $-E_a$
5. 5.

   According to the Arrhenius equation, how does an increase in temperature affect the reaction rate constant, and how does the magnitude of the activation energy influence this effect?

   • A) The rate constant increases, and a reaction with a higher activation energy experiences a greater proportional increase in rate constant.
   • B) The rate constant increases, and a reaction with a lower activation energy experiences a greater proportional increase in rate constant.
   • C) The rate constant decreases, and a reaction with a higher activation energy experiences a greater proportional decrease in rate constant.
   • D) The rate constant increases, and the proportional increase in rate constant is independent of the activation energy.