Q: Given the reaction $$2\mathrm{N}_2\mathrm{O}_5(g) \rightarrow 4\mathrm{NO}_2(g) + \mathrm{O}_2(g)$$, if the average rate of disappearance of $$\mathrm{N}_2\mathrm{O}_5 is$$ $$3.0 \times 10$$^{-1}$$\ \mathrm{M/s}$$, what is the average rate of formation of $$\mathrm{NO}_2$$?

$$6.0 \times 10$$^{-1}$$\ \mathrm{M/s}$$

Q: The decomposition of cyclopropane to propene follows first-order kinetics. If the rate constant $$k = 0.0399\ \text{min}^{-1}$$, what is the half-life of cyclopropane?

$$t_{1/2} = \dfrac{0.693}{0.0399}\ \text{min}$$

Question 1

Which of the following factors will NOT increase the rate of a chemical reaction?

Accepted Answer

Decreasing the surface area of a solid reactant

Question 2

The conversion of diamond to graphite is extremely slow at room temperature. Which best explains this observation?

Accepted Answer

The activation energy for the reaction is very high

Question 3

An airbag inflates rapidly in a car crash due to the decomposition of sodium azide: $$2\mathrm{NaN}_3(s) \rightarrow 2\mathrm{Na}(s) + 3\mathrm{N}_2(g). $$Which factor is most important for the reaction to occur quickly enough to protect the driver?

Accepted Answer

The sodium azide is finely powdered to increase surface area

Question 4

Given the reaction $$2\mathrm{N}_2\mathrm{O}_5(g) ightarrow 4\mathrm{NO}_2(g) + \mathrm{O}_2(g)$$, if the average rate of disappearance of $$\mathrm{N}_2\mathrm{O}_5 is$$ $$3.0 	imes 10$$^{-1}$$\ \mathrm{M/s}$$, what is the average rate of formation of $$\mathrm{NO}_2$$?

Accepted Answer

$$6.0 	imes 10$$^{-1}$$\ \mathrm{M/s}$$

Question 5

For the reaction $$2\mathrm{NO}(g) + \mathrm{Cl}_2(g) ightarrow 2\mathrm{NOCl}(g)$$ with the rate law $$	ext{Rate} = k[\mathrm{NO}]^2[\mathrm{Cl}_2]$$, what happens to the rate if $$[\mathrm{Cl}_2] is $$tripled and $$[\mathrm{NO}] is $$decreased by a factor of 4?

Accepted Answer

The rate decreases by a factor of $$\dfrac{3}{16}$$

Question 6

A reaction has the rate law $$	ext{Rate} = k[\mathrm{Br}_2]. $$What is the order of the reaction?

Accepted Answer

First order

Question 7

Given the following data for the reaction $$2A + B ightarrow C + D$$:
Experiment 1: $$[A]=0.10$$, $$[B]=0.05$$, Rate $$=6.0 	imes 10$$^{-3}$$ M/s
Experiment 2: $$[A]=0.20$$, $$[B]=0.05$$, Rate =1.2$$ 	imes $$10^{-2} M/s
$$Experiment 3: $$[A]=0.20$$, $$[B]=0.15$$, Rate $$=1.1 	imes 10$$^{-1}$$ M/s
What is the rate law?

Accepted Answer

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

Question 8

Which plot would be linear for a first-order reaction?

Accepted Answer

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

Question 9

The decomposition of cyclopropane to propene follows first-order kinetics. If the rate constant $$k = 0.0399\ 	ext{min}^{-1}$$, what is the half-life of cyclopropane?

Accepted Answer

$$t_{1/2} = \dfrac{0.693}{0.0399}\ 	ext{min}$$

Question 10

A first-order reaction has a rate constant $$k = 1.87 	imes 10$$^{-3}$$\ 	ext{min}^{-1}. If $$the initial concentration is $$4.73 	imes 10$$^{-4}$$\ 	ext{mol/L}$$, what is the concentration after 24 hours?

Accepted Answer

$$[A]_t = [A]_0 e$$^{-kt}$$

Question 11

The half-life of an organochlorine pesticide is 10 years. How many years will it take for the concentration to decrease to $$1/16 of $$its original value?

Accepted Answer

40 years

Question 12

For a second-order reaction $$2HI(g) ightarrow H_2$(g) + I_2$(g)$$ with $$k = 0.0308\ 	ext{M}^{-1}	ext{s}^{-1}$$, how long does it take for the concentration of HI to drop from 0.40 M to 0.20 M?

Accepted Answer

$$t = \dfrac{1}{k} \left( \dfrac{1}{[HI]_t} - \dfrac{1}{[HI]_0} \right)$$

Question 13

Which of the following statements about the rate constant $$k is $$TRUE?

Accepted Answer

The units of $$k$$ depend on the overall order of the reaction

Question 14

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It decreases the activation energy

Question 15

According to collision theory, which of the following is required for a reaction to occur?

Accepted Answer

Reactant molecules must collide with sufficient energy and proper orientation

Question 16

Which integrated rate law would you use to determine the concentration of a reactant at a given time for a zero-order reaction?

Accepted Answer

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

Question 17

A pesticide has a half-life of 3 days. How long will it take for the concentration to decrease to $$1/8 of $$its original value?

Accepted Answer

9 days

Question 18

Which of the following is a correct statement about the relationship between the rate of formation of $$O_2$$ and $$NO_2 in $$the reaction $$2N_2O_5(g) \rightarrow 4NO_2(g) + O_2$(g)$$?

Accepted Answer

The rate of formation of $$O_2 is $$one-fourth the rate of formation of $$NO_2$$

Chemical Kinetics: Reaction Rates and Rate Laws

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