Question 1

Which of the following statements about first-order reactions is TRUE?

Accepted Answer

A plot of $$\ln[A]_t$$ versus time yields a straight line with a slope of $$-k.$$

Question 2

For a reaction that is second order in $$A$$, which integrated rate law is correct?

Accepted Answer

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

Question 3

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

Accepted Answer

Second order

Question 4

You are given concentration vs. time data for a reaction. Which of the following would indicate the reaction is second order in $$A$$?

Accepted Answer

A plot of $$\dfrac{1}{[A]_t} vs. $$time is linear.

Question 5

The half-life of a first-order reaction is given by which equation?

Accepted Answer

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

Question 6

A piece of ancient wood contains $$0.125$$ times the amount of $$^{14}C as $$living wood. If the half-life of $$^{14}C is$$ $$5730$$ years, how old is the wood?

Accepted Answer

$$17190$$ years

Question 7

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 reaction.

Question 8

The Arrhenius equation is $$k = Ae$$^{-E_a/RT}$$. If the activation energy E_a$ increases, what happens to the rate constant k$ at a fixed temperature?

Accepted Answer

$$k$$ decreases

Question 9

For the reaction $$2NO_2(g) ightarrow 2NO(g) + O_2$(g)$$, the rate law is found to be $$	ext{Rate} = k[NO_2$]^2. If $$the initial concentration of $$NO_2 is$$ $$0.600\,M$$ and $$k = 0.543\,M$$^{-1}$$s^{-1}$$, what is the concentration of $$NO_2$$ after $$1$ hour?

Accepted Answer

$$0.011\,M$$

Question 10

Which of the following is TRUE about the half-life of a second-order reaction?

Accepted Answer

It is inversely proportional to the initial concentration.

Question 11

A reaction has a rate constant $$k$$ that increases by a factor of $$1.25$$ when the temperature is raised from $$298\,K to$$ $$500\,K. $$Which equation would you use to calculate the activation energy $$E_a$$?

Accepted Answer

$$\ln\left(\dfrac{k_2$}{k_1$}\right) = \dfrac{E_a}{R}\left(\dfrac{1}{T_1$} - \dfrac{1}{T_2$}\right)$$

Question 12

Which of the following is NOT a characteristic of a catalyst?

Accepted Answer

It changes the equilibrium position of the reaction.

Question 13

In a two-step reaction mechanism, which step determines the overall rate law?

Accepted Answer

The slowest (rate-determining) step

Question 14

Which of the following is a correct rate law for an elementary bimolecular reaction: $$A + B \rightarrow C$$?

Accepted Answer

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

Question 15

Which of the following statements about homogeneous and heterogeneous catalysis is TRUE?

Accepted Answer

Heterogeneous catalysis occurs on the surface of the catalyst.

Question 16

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

Accepted Answer

It provides a specific active site to lower the activation energy for the reaction.

Question 17

For a first-order reaction, if the rate constant $$k is$$ $$0.014\,s$$^{-1}$$, what is the half-life?

Accepted Answer

$$0.693/0.014 = 49.5\,s$$

Question 18

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

Accepted Answer

It refers to the number of molecules involved in the elementary step.

Question 19

Which of the following is a correct description of the orientation factor in the collision model?

Accepted Answer

Only collisions with the correct orientation and sufficient energy result in a reaction.

Kinetics: The Change of Concentration with Time (Integrated Rate Laws)

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