Question 1

A reaction is monitored by measuring the pressure of CH$$_3NC $$over time, and a plot of $$\ln(	ext{pressure})$$ versus time yields a straight line. What is the order of the reaction with respect to CH$$_3NC$$?

Accepted Answer

First order

Question 2

Given the integrated rate law for a first-order reaction $$\ln \frac{[A]_t}{[A]_0} = -kt$$, what is the half-life ($$t_{1/2}) $$expression for this reaction?

Accepted Answer

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

Question 3

A plot of $$1/[NO_2$]$$ versus time for the decomposition of $$NO_2 is $$linear. What is the order of the reaction with respect to $$NO_2$$?

Accepted Answer

Second order

Question 4

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

Accepted Answer

$$[A] vs. $$time

Question 5

Mercury(II) is eliminated from the body by a first-order process with a half-life of 6 days. If the initial concentration is $$8.0 	imes 10$$^{-6}$$ M, what is the concentration after 18 days?

Accepted Answer

$$2.0 	imes 10$$^{-6}$$ M

Question 6

Which of the following statements about the collision model of chemical reactions is FALSE?

Accepted Answer

The orientation of molecules during collision does not affect the reaction rate.

Question 7

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 given temperature?

Accepted Answer

It decreases

Question 8

A reaction mechanism consists of the following steps:
Step 1: $$O_3(g$$) + $$NO_2(g$$) \rightarrow $$NO_3(g$$) + $$O_2(g$$)$$ (slow)
Step 2: NO_3$(g) + NO_2$(g) \rightarrow N_2O_5(g) ($$fast)
What is the rate law for the overall reaction?

Accepted Answer

Rate = $$k[O_3$][NO_2$]$$

Question 9

Which of the following best describes an intermediate in a reaction mechanism?

Accepted Answer

A species that is formed in one step and consumed in a later step

Question 10

Consider the energy profile diagram for a reaction. What does the activation energy ($$E_a) $$represent?

Accepted Answer

The energy required to convert reactants to the activated complex

Question 11

For a reaction with the rate law $$	ext{Rate} = k[A][B]$$, what is the molecularity of the elementary step?

Accepted Answer

Bimolecular

Question 12

If a reaction is zero order in [A], how does the half-life change as the reaction proceeds?

Accepted Answer

It increases

Question 13

A plot of $$\ln k$$ versus $$1/T$$ yields a straight line with a negative slope. According to the Arrhenius equation, what does the magnitude of the slope represent?

Accepted Answer

$$-E_a/R$$

Question 14

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

Accepted Answer

It is independent of the initial concentration

Question 15

A reaction has a rate constant $$k_1 at $$temperature $$T_1$$ and $$k_2 at $$temperature $$T_2. $$Which equation allows you to calculate the activation energy $$E_a$$?

Accepted Answer

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

Question 16

Which of the following is a characteristic of a catalyst in a chemical reaction?

Accepted Answer

It provides an alternative pathway with a lower activation energy

Question 17

In a multistep reaction, which step determines the overall rate of the reaction?

Accepted Answer

The slowest step

Question 18

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

Accepted Answer

It increases the fraction of molecules with energy greater than $$E_a$$

Question 19

For the reaction $$2NO_2(g) \rightarrow 2NO(g) + O_2$(g)$$, the following data are collected:
Time (s): 0, 50, 100, 200, 300
$$[NO_2$] (M$$): 0.01000, 0.00787, 0.00649, 0.00481, 0.00380
Which plot would be linear if the reaction is second order in $$NO_2$$?

Accepted Answer

$$1/[NO_2$] vs. $$time

Question 20

Which of the following is NOT a requirement for a successful collision according to collision theory?

Accepted Answer

Reactant molecules must be in the gas phase

Integrated Rate Laws and Reaction Mechanisms in Chemical Kinetics

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