Q: For the reaction $$2NO_2(g) \rightarrow O_2$(g) + 2NO(g)$$, if the rate of disappearance of $$NO_2 is$$ $$4.0 \times 10$$^{-5}$$ \ \text{mol/L} \cdot \text{s}$$, what is the rate of appearance of $$O_2$$?

$$2.0 \times 10$$^{-5}$$ \ \text{mol/L} \cdot \text{s}$$

Q: The decomposition of $$N_2O_5 is $$first order with a rate constant $$k = 4.5 \times 10$$^{-3}$$ \ \text{s}^{-1}. $$What is the half-life of this reaction?

$$t_{1/2} = \frac{0.693}{k} = 154 \ \text{s}$$

Q: For the reaction $$2A \rightarrow B$$, the rate law is found to be $$\text{Rate} = k[A]^2. If $$the initial concentration of $$A is$$ $$0.10 M $$and the rate constant $$k is$$ $$0.50 \ \text{M}^{-1}\text{s}^{-1}$$, what is the initial rate?

$$0.0050 \ \text{M} \cdot \text{s}^{-1}$$

Question 1

Which of the following statements best explains why the conversion of diamond to graphite is considered spontaneous but is not observed in everyday life?

Accepted Answer

The reaction has a high activation energy, making the rate extremely slow.

Question 2

A reaction is found to be first order with respect to reactant A and zero order with respect to reactant B. Which of the following is the correct rate law for this reaction?

Accepted Answer

$$	ext{Rate} = k[A]$$

Question 3

Which of the following changes will NOT increase the rate of a chemical reaction?

Accepted Answer

Decreasing the temperature.

Question 4

For the reaction $$2NO_2(g) ightarrow O_2$(g) + 2NO(g)$$, if the rate of disappearance of $$NO_2 is$$ $$4.0 	imes 10$$^{-5}$$ \ 	ext{mol/L} \cdot 	ext{s}$$, what is the rate of appearance of $$O_2$$?

Accepted Answer

$$2.0 	imes 10$$^{-5}$$ \ 	ext{mol/L} \cdot 	ext{s}$$

Question 5

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

Accepted Answer

It lowers the activation energy, increasing the rate of both the forward and reverse reactions.

Question 6

The decomposition of $$N_2O_5 is $$first order with a rate constant $$k = 4.5 	imes 10$$^{-3}$$ \ 	ext{s}^{-1}. $$What is the half-life of this reaction?

Accepted Answer

$$t_{1/2} = \frac{0.693}{k} = 154 \ 	ext{s}$$

Question 7

Which graphical method would you use to determine if a reaction is second order with respect to reactant A?

Accepted Answer

Plot $$1/[A]$$ versus time and look for a straight line.

Question 8

Given the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what happens to the rate constant k$ if the activation energy E_a$ increases, assuming all other factors remain constant?

Accepted Answer

$$k$$ decreases.

Question 9

A reaction has the following rate law: $$	ext{Rate} = k[$$BrO_3$$^-][Br^-][H^+]^2. If $$the concentration of $$H^+ is $$doubled, by what factor does the rate increase?

Accepted Answer

4

Question 10

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

Accepted Answer

It is the slowest step and limits the overall reaction rate.

Question 11

In a catalytic converter, which process is primarily responsible for the conversion of CO and NO into less harmful products?

Accepted Answer

Heterogeneous catalysis on a solid surface.

Question 12

Which of the following best describes the difference between adsorption and absorption in the context of catalysis?

Accepted Answer

Adsorption is the collection of molecules on a surface; absorption is penetration into the bulk.

Question 13

For the reaction $$2A ightarrow B$$, the rate law is found to be $$	ext{Rate} = k[A]^2. If $$the initial concentration of $$A is$$ $$0.10 M $$and the rate constant $$k is$$ $$0.50 \ 	ext{M}^{-1}	ext{s}^{-1}$$, what is the initial rate?

Accepted Answer

$$0.0050 \ 	ext{M} \cdot 	ext{s}^{-1}$$

Question 14

Which of the following is a correct statement about the molecularity of an elementary reaction step?

Accepted Answer

Bimolecular steps involve the collision of two reactant molecules.

Question 15

A reaction is found to be zero order in reactant A. Which of the following is true about the rate of this reaction?

Accepted Answer

The rate is independent of the concentration of A.

Question 16

Which of the following best explains why coal dust is more explosive than a piece of charcoal?

Accepted Answer

Coal dust has a much greater surface area, increasing the rate of reaction.

Question 17

Which of the following is a correct integrated rate law for a first-order reaction?

Accepted Answer

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

Question 18

Which of the following is a true statement about the effect of temperature on reaction rate, according to the Arrhenius equation?

Accepted Answer

An increase in temperature increases the rate constant $$k$$ exponentially.

Question 19

Which of the following is a characteristic of a reaction intermediate?

Accepted Answer

It is produced in one step and consumed in another step of the mechanism.

Chemical Kinetics: Rates and Mechanisms of Chemical Reactions

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