Half-life of reactions Knowledge-Based Practice

Questions

1. 1.

   For a chemical reaction of the form A → products that obeys second-order kinetics, how does each successive half-life compare to the one preceding it as the reactant is consumed?

   • A) Each successive half-life remains constant throughout the reaction.
   • B) Each successive half-life is twice as long as the preceding half-life.
   • C) Each successive half-life is half as long as the preceding half-life.
   • D) Each successive half-life is four times as long as the preceding half-life.
2. 2.

   A certain first-order reaction requires 48 minutes for the reactant concentration to decrease to 12.5% of its initial value. What is the half-life of this reaction?

   • A) 6.0 minutes
   • B) 12 minutes
   • C) 24 minutes
   • D) 16 minutes
3. 3.

   For a certain chemical reaction, doubling the initial concentration of the reactant doubles the half-life of the reaction. What is the reaction order with respect to this reactant?

   • A) Zeroth order
   • B) First order
   • C) Second order
   • D) Third order
4. 4.

   A first-order reaction has a rate constant of $1.386 \times 10^{-2}\text{ min}^{-1}$. If the initial concentration of the reactant is 0.80 M, what is the concentration of the reactant remaining after 100 minutes?

   • A) 0.20 M
   • B) 0.40 M
   • C) 0.10 M
   • D) 0.05 M
5. 5.

   A decomposition reaction follows second-order kinetics with a rate constant of $0.050\text{ M}^{-1}\text{s}^{-1}$. What is the half-life of this reaction when the initial concentration of the reactant is $0.20\text{ M}$?

   • A) 14 s
   • B) 2.0 s
   • C) 100 s
   • D) 200 s

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