Q: The decomposition of a certain insecticide in water follows first-order kinetics with a rate constant $$k = 1.45~\text{yr}^{-1}. $$What is the half-life of the insecticide?

$$t_{1/2} = \dfrac{0.693}{1.45}~\text{yr}$$

Question 1

Which of the following best describes the rate law for the reaction $$2NO_2(g) \rightarrow 2NO(g) + O_2$(g) if $$experimental data shows that doubling $$[NO_2$]$$ quadruples the rate?

Accepted Answer

$$	ext{Rate} = k[NO_2$]^2$$

Question 2

A reaction is found to be first order in $$A$$ and zero order in $$B. $$Which of the following is the correct rate law?

Accepted Answer

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

Question 3

For the reaction $$A \rightarrow B$$, the concentration of $$A$$ decreases from 1.00 M to 0.54 M in 20 seconds. What is the average rate of disappearance of $$A$$ over this interval?

Accepted Answer

$$0.023~	ext{M/s}$$

Question 4

Which of the following changes will NOT increase the rate of a reaction between a solid and a gas?

Accepted Answer

Decreasing the concentration of the gas

Question 5

The decomposition of a certain insecticide in water follows first-order kinetics with a rate constant $$k = 1.45~	ext{yr}^{-1}. $$What is the half-life of the insecticide?

Accepted Answer

$$t_{1/2} = \dfrac{0.693}{1.45}~	ext{yr}$$

Question 6

Which of the following statements about catalysts is TRUE?

Accepted Answer

Catalysts provide an alternative reaction pathway with lower activation energy.

Question 7

A reaction has a rate law $$	ext{Rate} = k[A][B]^2. If$$ $$[A] is $$doubled and $$[B] is $$tripled, by what factor does the rate increase?

Accepted Answer

18

Question 8

Which of the following is the integrated rate law for a second-order reaction $$A \rightarrow$$ products?

Accepted Answer

$$\dfrac{1}{[A]_t} = kt + \dfrac{1}{[A]_0}$$

Question 9

The Arrhenius equation is given by $$k = Ae$$^{-E_a/RT}$$. What does A$ represent?

Accepted Answer

The frequency factor (related to collision frequency and orientation)

Question 10

A reaction is zero order in $$A. If $$the initial concentration of $$A is 0.50 M $$and the rate constant $$k = 0.10~	ext{M s}^{-1}$$, how long will it take for $$[A] to $$reach zero?

Accepted Answer

$$5.0~	ext{s}$$

Question 11

Which of the following best explains why increasing temperature generally increases the rate of a chemical reaction?

Accepted Answer

It increases the number of effective collisions per unit time.

Question 12

For the reaction $$2O_3(g) ightarrow 3O_2(g)$$, if the rate of disappearance of $$O_3 is$$ $$0.30~	ext{mol/L·s}$$, what is the rate of appearance of $$O_2$$?

Accepted Answer

$$0.45~	ext{mol/L·s}$$

Question 13

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

Accepted Answer

It determines the overall rate law for the reaction.

Question 14

A reaction has an activation energy of $$50~	ext{kJ/mol}. If $$the temperature increases from $$300~	ext{K} to$$ $$310~	ext{K}$$, what happens to the rate constant $$k$$?

Accepted Answer

It increases.

Question 15

Which of the following is a characteristic of a homogeneous catalyst?

Accepted Answer

It is in the same phase as the reactants.

Question 16

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

Accepted Answer

$$\ln[A] vs$$. $$t$$

Question 17

Which of the following is NOT a requirement for a plausible reaction mechanism?

Accepted Answer

All intermediates must appear as products.

Question 18

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

Accepted Answer

It lowers the activation energy barrier.

Question 19

Which of the following is true for the half-life of a second-order reaction?

Accepted Answer

It is inversely proportional to the initial concentration.

Question 20

Which of the following best explains why enzymes are highly specific catalysts?

Accepted Answer

Their active site has a unique shape that fits only specific substrates.

Chemical Kinetics: Principles, Rate Laws, and Mechanisms

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