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Chem II > Ch 14 > Flashcards

Ch 14 Flashcards

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1
Q

Nitrogen dioxide reacts with carbon monoxide to produce nitrogen monoxide and carbon dioxide.
NO2(g) + CO(g) → NO(g) + CO2(g)
A proposed mechanism for this reaction is
2 NO2(g) NO3(g) + NO(g) (fast, equilibrium)
NO3(g) + CO(g) → NO2(g) + CO2(g) (slow)
What is a rate law that is consistent with the proposed mechanism?

rate = k[NO2]2[CO] [NO]–1
rate = k[NO2]2[CO]
rate = k[NO2][CO]
rate = k[NO3][CO]
rate = k[NO2]2

A

a.

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2
Q

For the reaction A + 2B → C, the rate law is
.
What are the units of the rate constant where time is measured in seconds?

A

b.

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3
Q

The reaction kinetics for a certain reaction are studied over several temperatures. Which of the following is/are not effected by a change in reaction temperature?
the reaction rate
the rate constant, k
the energy of activation, Ea
a and b
a, b, and c

A

c.

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4
Q

In general, as temperature increases, the rate of a chemical reaction
decreases due to fewer collisions with proper molecular orientation.
increases for exothermic reactions, but decreases for endothermic reactions.
increases due to a greater number of effective collisions.
remains unchanged.
decreases due to an increase in the activation energy.

A

c.

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5
Q

For the overall reaction
2A + B → C
which of the following mechanisms is/are consistent with a rate equation of rate = k[A]2[B]?

A + B I (fast)
I + A → C (slow)
A + B → I (slow)
I + A → C (fast)
2A → I (slow)
B + I → C (fast)
2A I (fast)
I + B → C (slow)
Answers a and d are both correct.

A

e.

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6
Q

The _____ of an elementary step is defined as the number of reactant molecules that come together in a reaction.

A

molecularity

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7
Q

Which of the following is not a correct representation of the integrated rate expression for a decomposition first-order reaction?

A

e.

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8
Q

Which of the following statements is correct for the first-order reaction: A → 2B?
The concentration of A decreases linearly with respect to time.
The concentration of A is constant with respect to time.
The natural logarithm of the concentration of A decreases linearly with respect to time.
The rate of reaction is constant with respect to time.
The rate constant, k, of the reaction decreases linearly with respect to time.

A

c.

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9
Q

The Arrhenius equation, expresses the dependence of the rate constant on the reaction temperature. The slope of a plot of ln(k) versus 1/T is equal to

A

e.

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10
Q

In a reaction coordinate diagram, reacting molecules are most unstable ______.
at their initial position
when they are about to collide
right after they collide
at the transition state

A

d.

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11
Q

Which of the following statements is true of the Arrhenius equation?
Group of answer choices

The factor always has a value more than 1.

Ea represents the fraction of molecules having the minimum energy required for a reaction.

It can be used to calculate Ea from the temperature dependence of the rate constant.

It can be used to calculate the rate constant if is known.

The factor always has a value more than 10.

A

c.

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12
Q

The pre-exponential, A, in the Arrhenius equation is called the ________ factor.

A

frequency

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13
Q

Molecules must overcome a barrier called the activation energy if they are to react. The highest energy point reached during the progress of a reaction is called the ____.
Group of answer choices

rate determining step

transition state

half-life

elementary step

intermediate state

A

b.

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14
Q

Which of the following is the effect of adding a catalyst to a reaction?
Group of answer choices

Increase in the number of collisions between reactants

Lowering of the activation energy of a reaction

Increase in the equilibrium constant of a reaction

Decrease in the yield of the products

Increase in the enthalpy change of a reaction

A

b.

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15
Q

Which of the following units are consistent with the units of the reaction rate in a first order reaction?

A

a.

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16
Q

Which of the following steps must occur for an enzyme to catalyze a reaction?
Group of answer choices

The reactant, often called the substrate, must bind to the enzyme.

The chemical reaction must be halted.

The products of the reaction must attach to the enzyme.

The quantity of the enzymes in the reaction should keep increasing.

The reactant must bind to the product rather than the enzyme.

A

a.

17
Q

A student analyzed a first-order reaction and obtained the graph below. Unfortunately, the student forgot to label the axes. What are the correct labels for the x and y axes?

x axis = time, y axis = ln[A]

x axis = ln[time], y axis = [A]

x axis = ln[time], y axis = [A]

x axis = time, y axis = 1/[A]

x axis = 1/time, y axis = 1/[A]

A

a.

18
Q

For the zero-order reaction A → B + C, a graph of _____ versus time will generate a straight line.

A

a.

19
Q

A catalyst ____.
Group of answer choices

is used up in a chemical reaction

changes the potential energy change of the reaction

is always a solid

does not influence the reaction in any way

changes the activation energy of the reaction

A

e.

20
Q

Circle the catalyst in the following mechanism.

A
21
Q

For the overall reaction A + 2B → C, which of the following mechanisms yields the correct overall chemical equation and is consistent with the rate equation below?

A + B I (fast)
I + A → C (slow)
A + B → I (slow)
I + B → C (fast)
2B → I (slow)
A + I → C (fast)
2B I (fast)
I + A → C (slow)
A + 2B I (fast)
I + B → C + B (slow)

A

b.

22
Q

Consider the exothermic combustion of coal. Which of the following could increase the rate of reaction?
Group of answer choices

Using smaller pieces of coal

Increasing the concentration of oxygen

Lowering the temperature

Both a and b are correct.

None of these

A

d.

23
Q

If a reaction is second-order with respect to a particular reactant, when the concentration of that reactant is increased by a factor of 4, the reaction rate will _____.
Group of answer choices

increase by a factor of 16.

remain constant.

decrease by a factor of .

increase by a factor of 64.

decrease by a factor of .

A

a.

24
Q

The elementary steps for the catalyzed decomposition of dinitrogen monoxide are shown below.
N2O(g) + NO(g) → N2(g) + NO2(g)
NO2(g) → NO(g) + 1/2 O2(g)
Which of the following statements is/are CORRECT?
1. The overall balanced reaction is N2O(g) → N2(g) + 1/2 O2(g).
2. NO2(g) is a catalyst for the reaction.
3. NO(g) is a reaction intermediate.
Group of answer choices

1 only

2 only

3 only

1 and 3

1, 2, and 3

A

a.

25
Q

What is the name given to a substance that increases the rate of a chemical reaction but is not itself consumed?
catalyst
reactant
intermediate
enthalpy
rate constant

A

a.

26
Q

According to collision theory, which condition(s) must be met in order for molecules to react?
1. The reacting molecules must collide with sufficient energy to initiate the process of breaking and forming bonds.
2. A catalyst must be in contact with the reacting molecules for a reaction to occur.
3. The reacting molecules must collide with an orientation that can lead to rearrangement of the atoms.
Group of answer choices

1 only

2 only

3 only

1 and 2

1 and 3

A

e.

27
Q

A suggested mechanism for the decomposition of ozone is as follows:
O3 O2 + O fast equilibrium
O + O3 2O2 slow step
What is the rate law predicted by this mechanism?

A

c.

28
Q

Which statement concerning relative rates of reaction is correct for the chemical equation given below?
2 CH3OH(g) + 3 O2(g) → 2 CO2(g) + 4 H2O(g)
Group of answer choices

The rate of disappearance of CH3OH is equal to the rate of disappearance of O2.

The rate of disappearance of CH3OH is two times the rate of appearance of H2O.

The rate of disappearance of CH3OH is half the rate of appearance of CO2.

The rate of appearance of H2O is two times the rate of appearance of CO2.

The rate of appearance of H2O is four times the rate of disappearance of CH3OH.

A

d.

29
Q

Radioactive isotopes decay by ________-order kinetics.

A

first

30
Q

Termolecular elementary steps are rare. Why?

A

because it has three reactants

31
Q

How are the exponents in a rate law determined?
Group of answer choices

They are equal to the inverse of the coefficients in the overall balanced chemical equation.

They are determined by experimentation.

They are equal to the coefficients in the overall balanced chemical equation.

They are equal to the reactant concentrations.

They are equal to the ln(2) divided by the rate constant.

A

not a. or d.

32
Q

If a catalyst is present in a different phase from the reactants and products, it is referred to as a(n) ________ catalyst.

A

maybe enzyme

33
Q

For the hypothetical reaction aA → products, the experimental data showed the following behavior (below). What is the reaction order with respect to reactant A?

A

b.

34
Q

For the reaction A → B + C, which of the following equations corresponds to the integrated expression for a second-order decomposition reaction?

A

e.

35
Q

The Arrhenius equation, , relates the rate constant of reaction and temperature. A plot of ____ versus 1/T will yield a straight line with a slope of –Ea/R.

A

c.

36
Q

Which of the following is/are expected to affect the rate of a chemical reaction?
1. Addition of a catalyst.
2. Decreasing the reactant concentrations.
3. Increasing the reactant volumes but leaving the concentrations the same.
Group of answer choices

1 only

2 only

3 only

1 and 2

1, 2, and 3

A

d.

37
Q

Which of the given relationships correctly compares the rates of the reactants and products for the reaction below?

A

not b. or d.

38
Q

Consider the following proposed mechanism. If this mechanism for the overall reaction were correct, and if k1 were much less than k2, then the observed rate law would be
2A C + I
I + B C + D
Group of answer choices

rate = k1[A]

rate = k2[I][B]
c.
rate = k1[A]2

rate = k1[A]2 − k2[C][D]

rate = k1k2[A]2[I][B]

A

c.

39
Q

How many mechanistic steps are depicted by in this potential energy diagram?

one step

two steps

three steps

four steps

five steps

A

not b.

Chem II (13 decks)

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