Q: The decomposition of $$N_2O_5 is a $$first-order reaction. If the initial concentration is $$0.100\ \mathrm{M}$$ and after $$2000\ \mathrm{s}$$ the concentration is $$0.050\ \mathrm{M}$$, what is the rate constant $$k$$?

$$k = 3.47 \times 10$$^{-4}$$\ \mathrm{s}^{-1}$$

Question 1

Which of the following changes will increase the rate of a heterogeneous reaction involving a solid and a gas?

Accepted Answer

Grinding the solid into a fine powder

Question 2

For the reaction $$2O_3(g) \rightarrow 3O_2(g)$$, if the rate of disappearance of ozone is $$0.10\ \mathrm{M/s}$$, what is the rate of appearance of $$O_2$$?

Accepted Answer

$$0.15\ \mathrm{M/s}$$

Question 3

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

Accepted Answer

$$\mathrm{Rate} = k[A][B]^2$$

Question 4

The decomposition of $$N_2O_5 is a $$first-order reaction. If the initial concentration is $$0.100\ \mathrm{M}$$ and after $$2000\ \mathrm{s}$$ the concentration is $$0.050\ \mathrm{M}$$, what is the rate constant $$k$$?

Accepted Answer

$$k = 3.47 	imes 10$$^{-4}$$\ \mathrm{s}^{-1}$$

Question 5

Which of the following statements about catalysts is TRUE?

Accepted Answer

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

Question 6

Given the reaction $$A + 2B \rightarrow 3C$$, if $$[A] is $$decreasing at $$0.020\ \mathrm{M/s}$$, at what rate is $$[C]$$ increasing?

Accepted Answer

$$0.030\ \mathrm{M/s}$$

Question 7

The rate law for a reaction is $$\mathrm{Rate} = k[NO_2$]^2. If $$the concentration of $$NO_2 is $$doubled, how does the rate change?

Accepted Answer

It quadruples

Question 8

Which of the following best describes the transition state in a chemical reaction?

Accepted Answer

The highest energy point along the reaction pathway

Question 9

A plot of $$\ln[A]$$ versus time for a reaction yields a straight line with a negative slope. What is the order of the reaction with respect to $$A$$?

Accepted Answer

First order

Question 10

The Arrhenius equation is $$k = Ae$$^{-E_a/RT}$$. If the activation energy E_a$ is decreased, what is the effect on the rate constant k$?

Accepted Answer

The rate constant increases

Question 11

For a reaction with the rate law $$\mathrm{Rate} = k[A][B]$$, what are the units of the rate constant $$k if $$the rate is in $$\mathrm{M/s}$$?

Accepted Answer

$$\mathrm{M}^{-1}\mathrm{s}^{-1}$$

Question 12

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

Accepted Answer

All intermediates must appear in the overall reaction.

Question 13

A reaction has a half-life that is independent of the initial concentration. What is the order of the reaction?

Accepted Answer

First order

Question 14

In the mechanism below, which species is an intermediate?

Step 1: $$A + B \rightarrow X + Y$$
Step 2: $$X + C \rightarrow Y + Z$$

Accepted Answer

$$X$$

Question 15

If a reaction is zero order in $$A$$, what will happen to the rate if $$[A] is $$doubled?

Accepted Answer

The rate will remain the same

Question 16

A certain reaction has the following rate law: $$\mathrm{Rate} = k[H_2$][I_2$]. If $$the initial concentrations are $$[H_2$] = 0.10\ \mathrm{M}$$ and $$[I_2$] = 0.20\ \mathrm{M}$$, and the rate constant $$k = 2.0\ \mathrm{M}^{-1}\mathrm{s}^{-1}$$, what is the initial rate?

Accepted Answer

$$0.0040\ \mathrm{M/s}$$

Question 17

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

Accepted Answer

It increases the number of collisions and the fraction of molecules with sufficient energy to overcome the activation energy.

Question 18

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

Accepted Answer

$$1/[A] vs$$. $$t$$

Question 19

A reaction has an activation energy of $$80\ \mathrm{kJ/mol}. If $$the temperature is increased from $$300\ \mathrm{K} to$$ $$310\ \mathrm{K}$$, what happens to the rate constant $$k$$?

Accepted Answer

It increases slightly

Question 20

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

Accepted Answer

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

Chemical Kinetics: Principles and Factors Affecting Reaction Rates

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