Q: Which of the following is the correct unit for the rate constant k for a second-order reaction?

$$\text{mol}^{-1} \text{L} \text{s}^{-1}$$

Q: Which of the following is the correct expression for the rate of disappearance of H$$_2 in $$the reaction $$\text{H}_2(g) + \text{I}_2(g) \rightarrow 2 \text{HI}(g)$$?

$$\text{Rate} = -\frac{d[\text{H}_2]}{dt}$$

Question 1

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst decreases the activation energy, making the reaction faster.

Question 2

For the reaction $$2	ext{NO}_2(g) ightarrow 2	ext{NO}(g) + 	ext{O}_2(g)$$, the experimentally determined rate law is $$	ext{Rate} = k[	ext{NO}_2]^2. $$Which of the following statements is true?

Accepted Answer

The reaction is second order with respect to NO$$_2.$$

Question 3

A reaction is found to be first order in A. Which integrated rate law would you use to determine the concentration of A at time t?

Accepted Answer

$$\ln [A]_t = -kt + \ln [A]_0$$

Question 4

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

The color of the reactants

Question 5

The half-life for a first-order reaction is given by which of the following expressions?

Accepted Answer

$$t_{1/2} = \frac{0.693}{k}$$

Question 6

Given the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what will happen to the rate constant k if the temperature is increased?

Accepted Answer

k will increase.

Question 7

A reaction has a rate law $$	ext{Rate} = k[A][B]^2. $$What is the overall order of the reaction?

Accepted Answer

Third order

Question 8

Which of the following best explains why increasing the concentration of reactants generally increases the rate of reaction?

Accepted Answer

It increases the frequency of effective collisions.

Question 9

For a second-order reaction, which plot yields a straight line?

Accepted Answer

$$\frac{1}{[A]} vs. $$time

Question 10

Which of the following statements about catalysts is FALSE?

Accepted Answer

Catalysts change the equilibrium position of a reaction.

Question 11

A reaction is zero order in reactant A. If the initial concentration of A is doubled, what happens to the rate?

Accepted Answer

The rate remains the same.

Question 12

Which of the following is the correct unit for the rate constant k for a second-order reaction?

Accepted Answer

$$	ext{mol}^{-1} 	ext{L} 	ext{s}^{-1}$$

Question 13

Which of the following is a valid reason why enzymes are essential for metabolism?

Accepted Answer

They allow reactions to occur at body temperature by lowering activation energy.

Question 14

If a reaction mechanism consists of a fast equilibrium followed by a slow step, which step determines the rate law?

Accepted Answer

The slow step

Question 15

Which of the following best describes a heterogeneous catalyst?

Accepted Answer

It is in a different phase than the reactants.

Question 16

A reaction has an activation energy of 50 kJ/mol. If the temperature is increased from 300 K to 310 K, what happens to the rate constant k?

Accepted Answer

k increases slightly

Question 17

Which of the following is true for the rate-determining step in a reaction mechanism?

Accepted Answer

It is the slowest step and determines the overall rate law.

Question 18

Which of the following is the correct expression for the rate of disappearance of H$$_2 in $$the reaction $$	ext{H}_2(g) + 	ext{I}_2(g) ightarrow 2 	ext{HI}(g)$$?

Accepted Answer

$$	ext{Rate} = -\frac{d[	ext{H}_2]}{dt}$$

Question 19

Which of the following is an intermediate in a reaction mechanism?

Accepted Answer

A species that is formed in one step and consumed in a later step.

Question 20

Which of the following best describes the effect of increasing temperature on the Maxwell-Boltzmann distribution of molecular energies?

Accepted Answer

The distribution shifts to higher energies, increasing the fraction of molecules with energy greater than $$E_a.$$

Chemical Kinetics: Rates, Mechanisms, and Catalysis

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