Q: A reaction is found to be first order in A. Which integrated rate law correctly describes the concentration of A as a function of time?

$$\ln[A] = -kt + \ln[A]_\text{initial}$$

Question 1

Which of the following best describes the effect of increasing the concentration of reactants on the rate of a chemical reaction?

Accepted Answer

The reaction rate increases because more reactant molecules lead to more frequent collisions.

Question 2

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

Accepted Answer

3

Question 3

A reaction is found to be first order in A. Which integrated rate law correctly describes the concentration of A as a function of time?

Accepted Answer

$$\ln[A] = -kt + \ln[A]_	ext{initial}$$

Question 4

Which of the following statements about catalysts is correct?

Accepted Answer

Catalysts provide an alternative reaction pathway with a lower activation energy.

Question 5

Given the following data for a reaction: $$[	ext{A}]_0 = 0.56\,M$$, $$[	ext{A}]_{40s} = 0.28\,M$$, calculate the average rate over 40 seconds.

Accepted Answer

$$0.0070\,M/s$$

Question 6

Which of the following is the correct rate law for an elementary bimolecular step involving A and B?

Accepted Answer

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

Question 7

A reaction has a rate constant $$k$$ with units of $$M^{-1}$$ $$s^{-1}. $$What is the order of the reaction?

Accepted Answer

Second order

Question 8

Which of the following best explains why powdered solids react faster than blocks of the same substance?

Accepted Answer

Powdered solids have a greater surface area, allowing more collisions with reactant molecules.

Question 9

The half-life of a first-order reaction is given by $$t_{1/2} = \frac{0.693}{k}. If$$ $$k = 0.035\,s$$^{-1}$$, what is the half-life?

Accepted Answer

$$19.8\,s$$

Question 10

Which of the following is NOT a valid method for measuring the rate of a chemical reaction?

Accepted Answer

Measuring the change in temperature using a thermometer

Question 11

For a reaction with the rate law $$	ext{Rate} = k[A]^0$$, which of the following statements is true?

Accepted Answer

The rate is independent of the concentration of A.

Question 12

Which of the following best describes the role of the rate-determining step in a reaction mechanism?

Accepted Answer

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

Question 13

The Arrhenius equation in two-point form is $$\ln\left(\frac{k_2$}{k_1$}\right) = \frac{E_a}{R}\left(\frac{1}{T_1$} - \frac{1}{T_2$}\right). $$What does $$E_a$$ represent?

Accepted Answer

The activation energy of the reaction

Question 14

Which of the following is a correct statement about intermediates in a reaction mechanism?

Accepted Answer

Intermediates are produced in one step and consumed in a subsequent step.

Question 15

Which of the following is a real-world example of a heterogeneous catalyst?

Accepted Answer

A solid catalytic converter in a car’s exhaust system

Question 16

Which of the following best describes the function of an enzyme in a biological reaction?

Accepted Answer

It binds to the substrate at the active site, lowering the activation energy for the reaction.

Question 17

Which of the following is a correct statement about the effect of temperature on reaction rate?

Accepted Answer

Increasing temperature increases the rate constant $$k$$ for most reactions.

Question 18

Which of the following is a correct statement about the ozone layer?

Accepted Answer

Ozone in the stratosphere absorbs harmful UV radiation, protecting living organisms.

Question 19

A reaction is second order in A. If the initial concentration of A is doubled, how does the initial rate change?

Accepted Answer

The rate increases by a factor of 4.

Question 20

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

Accepted Answer

Molecularity refers to the number of reactant particles involved in a single elementary step.

Chemical Kinetics: Rates, Mechanisms, and Catalysis

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