Practice Questions

Front 1

Indicate which of the following compounds is a component of photochemical smog.

a. H2O
b. CO2
c. N2O
d. O3
e. CO

Back 1

d

Front 2

At what time of day are ozone concentrations highest during a photochemical smog event?

a. in the morning before rush hour

b. in the morning just after rush hour

c. midmorning

d. noon

e. midafternoon

Back 2

e

Front 3

One reaction that occurs in an automobile catalytic converter is the conversion of nitrogen monoxide to nitrogen and oxygen. How is the rate of this reaction related to the rate at which the concentration of a reactant or product changes? 2NO(g) → N2(g) + O2(g)

I. Rate = Δ[NO]/Δt

II. Rate = –Δ[NO]/Δt

III. Rate = Δ[N2]/Δt

IV. Rate = Δ[O2]/Δt

Back 3

III and IV only

Front 4

One reaction that occurs in an automobile catalytic converter is the conversion of carbon monoxide to carbon dioxide. How is the rate of this reaction related to the rate at which the concentration of a reactant or product changes? 2CO(g) + O2(g) → 2CO2(g)

I. Rate = Δ[CO]/Δt

II. Rate = –Δ[CO]/Δt

III. Rate = –Δ[O2]/Δt

IV. Rate = Δ[CO2]/Δt

Back 4

III only

Front 5

Which of the following is not a possible graph of concentration versus time for a reactant?

Back 5

c

Front 6

The following graph shows the kinetics curves for the reaction of oxygen with hydrogen to form water: O2(g) + 2H2(g) → 2H2O(g). Which curve is hydrogen?

Back 6

the black curve

Front 7

Ammonia gas (NH3) is produced from hydrogen and nitrogen gas according to the following reaction: 3H2(g) + N2(g) → 2NH3(g)If the rate of production of ammonia is R(NH3), what is the rate of loss of hydrogen and nitrogen gas,respectively?

Back 7

–R(H2) = 3/2 R(NH3); –R(N2) = 1/2 R(NH3)

Front 8

What are the units for the rate constant in a second-order reaction?

Back 8

M– 1 s– 1

Front 9

Which of the following plots indicates that the reaction is zero order?

Back 9

a

Front 10

Which of the following plots indicates that the reaction is second order?

Back 10

d

Front 11

The energy needed to form an activated complex is called ________

Back 11

activation energy

Front 12

The energy profiles for four different reactions are shown below. The scales are the same for each. Which reaction is the most exothermic?

Back 12

a

Front 13

The following figure shows Arrhenius plots for four different reactions. Which reaction has the lowest activation energy?

Back 13

b

Front 14

The following figure shows Arrhenius plots for four different reactions. Which reaction has the least temperature dependence?

Back 14

a

Front 15

Which of the following must be true of an intermediate in a reaction mechanism? An intermediate is________

I. produced by an elementary step II. consumed in an elementary step III. not included in the overall balanced reaction equation.

Back 15

all of the above

Front 16

A proposed mechanism for the decomposition of ozone in the atmosphere is:

Step 1: Cl(g) + O3(g) → ClO(g) + O2(g)

Step 2: ClO(g) + O3(g) → Cl(g) + 2 O2(g)

Which of the following species is an intermediate?

Back 16

CLO

Front 17

A proposed mechanism for the decomposition of ozone in the stratosphere is:

Step 1: Cl(g) + O3(g) → ClO(g) + O2(g)

Step 2: ClO(g) + O3(g) → Cl(g) + 2O2(g)

What is the molecularity of step 1?

Back 17

bimolecular

Front 18

A catalyst that is in the same phase as the reactants and products is a(n) ________ catalyst.

Back 18

homogeneous

Front 19

Which of the following statements must be true of a catalyst in a reaction mechanism?

I. Is consumed in an elementary step.

II. Is regenerated in an elementary step after it is consumed.

III. Is included in the overall balanced reaction equation.

Back 19

I and II

Front 20

During a spontaneous chemical reaction, it is found that ΔSsys < 0. This means ________

Back 20

ΔSsurr > 0 and its magnitude is > ΔSsys.

Front 21

ΔSsys can be directly related to the heat, q. Which of statements A–D is not true regarding this relationship?If all are true, select E.

a. ΔSsys can always be determined from the heat transferred during the actual process.

b. For a reversible spontaneous endothermic process, both q and ΔSsys will be positive.

c. The more heat that is transferred, the larger the magnitude of the entropy change.

d. The higher the temperature at which heat is transferred, the lower the entropychange.

Back 21

a

Front 22

The entropy change of the surroundings, ΔSsurr, is related to heat transfer, q, with respect to the system and temperature T by ________

Back 22

–q/Tsurr = ΔSsurr.

Front 23

Which of the following must be true for a spontaneous exothermic process?

a. only that ΔSsys < 0

b. only that ΔSsys > 0

c. both ΔSsys < 0 and the magnitude of ΔSsys < the magnitude of ΔSsurr

d. both ΔSsys < 0 and the magnitude of ΔSsys > the magnitude of ΔSsurr

e. either ΔSsys > 0 or ΔSsys < 0 and the magnitude of ΔSsys < the magnitude of ΔSsurr

Back 23

e

Front 24

36. Which of the following is in the correct order of standard state entropy?

I. Diamond < graphite

II. Liquid water < solid water

III. NH3 < H2

Back 24

I only

Front 25

Which of the relationships between the free-energy change of a system and associated entropy changes istrue?

a. ΔGsys = +T ΔSsystem

d. ΔGsys = –T ΔSsurroundings

b. ΔGsys = –T ΔSsystem

e. ΔGsys = –T ΔSuniverse

c. ΔGsys = +T ΔSuniverse

Back 25

e

Front 26

What is the difference between ΔG and ΔG°?

Back 26

d. ΔG° refers to the conversion of reactants in their standard state to products in their standard state; ΔG is defined for a reaction under any conditions.

Front 27

At constant T and P, any reaction will be spontaneous if ΔGsys _ 0

Back 27

<

Front 28

How many entries are incorrect?

Back 28

2

Front 29

Which of the following must be true for a reaction to proceed to form products?

a. Q > K, ΔG < 0, and ΔG° < 0

b. Q < K and ΔG < 0, ΔG° can be anything

c. Q > K and ΔG° < 0, ΔG can be anything

d. Q < K, ΔG < 0, ΔG° < 0

e. Q < K and ΔG° < 0, ΔG can be anything<

Back 29

b

Front 30

If for a given chemical reaction at 298 K, both the change in free energy, ΔG, and the change in the standard free energy, ΔG°, are positive with ΔG > ΔG°, then ________

a. Q > K and product is turning back into reactant.

b. Q > K and more product is being produced.

c. Q < K and product is turning back into reactant.

d. Q < K and more product is being produced.

e. Q = K and the reaction has stopped

Back 30

a

Front 31

As T approaches infinity, ln K approaches ______

Back 31

Front 32

What types of motion does a molecule of chlorine have?

a. translational, rotational, vibrational

b. kinetic energy and potential energy

c. microstate and macrostate

d. Boltzmann and non-Boltzmann

e. all of the above

Back 32

a

Front 33

which letter shoes the activation energy (without use of catalyst)?

Back 33

a

Front 34

which letter shoes the activation energy using a catalyst

Back 34

e

Front 35

which letter shoes the change in energy for the overall reaction

Back 35

d

Front 36

Back 36

I-

Front 37

Back 37

d

Front 38

Back 38

0

Front 39

Back 39

c

Front 40

Back 40

c

Front 41

Back 41

II

Front 42

Back 42

b

Front 43

Back 43

d