Q: Which of the following best describes the reaction rate for the hypothetical reaction $$aA + bB \rightarrow cC + dD$$?

$$\text{Rate} = -\frac{1}{a} \frac{\Delta [A]}{\Delta t} = -\frac{1}{b} \frac{\Delta [B]}{\Delta t} = \frac{1}{c} \frac{\Delta [C]}{\Delta t} = \frac{1}{d} \frac{\Delta [D]}{\Delta t}$$

Q: A reaction is found to be second order in $$[NO]$$ and first order in $$[H_2$]. $$What is the correct rate law for this reaction?

$$\text{Rate} = k[NO]^2[H_2$]$$

Q: The decomposition of cyclopropane at $$1000^\circ C$$ follows first-order kinetics with a rate constant $$k = 9.2\ \text{s}^{-1}. $$What is the half-life of the reaction?

$$t_{1/2} = \frac{0.693}{k} = \frac{0.693}{9.2\ \text{s}^{-1}}$$

Question 1

Which of the following best describes the reaction rate for the hypothetical reaction $$aA + bB \rightarrow cC + dD$$?

Accepted Answer

$$	ext{Rate} = -\frac{1}{a} \frac{\Delta [A]}{\Delta t} = -\frac{1}{b} \frac{\Delta [B]}{\Delta t} = \frac{1}{c} \frac{\Delta [C]}{\Delta t} = \frac{1}{d} \frac{\Delta [D]}{\Delta t}$$

Question 2

A reaction is found to be second order in $$[NO]$$ and first order in $$[H_2$]. $$What is the correct rate law for this reaction?

Accepted Answer

$$	ext{Rate} = k[NO]^2[H_2$]$$

Question 3

Which of the following statements about catalysts is TRUE?

Accepted Answer

A catalyst provides an alternative reaction pathway with a lower activation energy.

Question 4

For a first-order reaction, which of the following plots will yield a straight line?

Accepted Answer

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

Question 5

The decomposition of cyclopropane at $$1000^\circ C$$ follows first-order kinetics with a rate constant $$k = 9.2\ 	ext{s}^{-1}. $$What is the half-life of the reaction?

Accepted Answer

$$t_{1/2} = \frac{0.693}{k} = \frac{0.693}{9.2\ 	ext{s}^{-1}}$$

Question 6

Which factor does NOT affect the rate constant $$k of a $$reaction?

Accepted Answer

The concentration of reactants

Question 7

According to collision theory, why does increasing the temperature generally increase the reaction rate?

Accepted Answer

More molecules have sufficient energy to overcome the activation energy barrier.

Question 8

Given the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what is the effect of increasing the activation energy E_a$ on the rate constant k$?

Accepted Answer

The rate constant $$k$$ decreases.

Question 9

A reaction has the rate law $$	ext{Rate} = k[A]. If $$the initial concentration of $$A is $$doubled, what happens to the rate?

Accepted Answer

The rate doubles.

Question 10

For a second-order reaction with respect to $$A$$, which integrated rate law is correct?

Accepted Answer

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

Question 11

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

Accepted Answer

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

Question 12

The half-life for a zero-order reaction is given by which expression?

Accepted Answer

$$t_{1/2} = \frac{[A]_0}{2k}$$

Question 13

Which of the following best explains why a catalyst does not affect the equilibrium position of a reaction?

Accepted Answer

It lowers the activation energy for both the forward and reverse reactions equally.

Question 14

A reaction is zero order in $$[A]. If$$ $$[A] is $$plotted versus time, what will the graph look like?

Accepted Answer

A straight line with a negative slope.

Question 15

Which of the following is a requirement for a proposed reaction mechanism to be valid?

Accepted Answer

The sum of the elementary steps must equal the overall reaction.

Question 16

If the rate law for a reaction is $$	ext{Rate} = k[A]^2$$, what are the units of the rate constant $$k$$?

Accepted Answer

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

Question 17

Which of the following best describes the effect of increasing reactant concentration on the rate of a reaction, according to collision theory?

Accepted Answer

It increases the number of collisions, thus increasing the reaction rate.

Question 18

A reaction has the following rate law: $$	ext{Rate} = k[NO_2$]^2. If $$the concentration of $$NO_2 is $$tripled, by what factor does the rate increase?

Accepted Answer

9

Question 19

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

Accepted Answer

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

Question 20

Which of the following statements about the activation energy ($$E_a) is $$correct?

Accepted Answer

It is the minimum energy required for a reaction to occur.

Chemical Kinetics: Principles, Rate Laws, and Mechanisms

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