Deck 13: Chemical Kinetics

Question 1

For the following reaction, $\Delta$ P(C₆H₁₄)/ $\Delta$ t was found to be -6.2 * 10^-3 atm/s.C₆H₁₄(g) $\rarr$ C₆H₆(g) + 4H₂(g) Determine $\Delta$ P(H₂)/ $\Delta$ t for this reaction at the same time.

A) 6.2 * 10^-3 atm/s
B) 1.6 * 10^-3 atm/s
C) 2.5 * 10^-2 atm/s
D) -1.6 * 10^-3 atm/s
E) -2.5 * 10^-2 atm/s

Answer 1

2.5 * 10^-2 atm/s

Question 2

Use the following data to determine the rate law for the reaction shown below.2NO + H₂ $\rarr$ N₂O + H₂O $\begin{array}{lccc} Expt.\# &[\mathrm{NO}]_{0}&\left[\mathrm{H}_{2}\right]_{0}&Initial~ rate \\\hline1 & 0.021 & 0.065 & 1.46 \mathrm{M} / \mathrm{min} \\2 & 0.021 & 0.260 & 1.46 \mathrm{M} / \mathrm{min} \\3 & 0.042 & 0.065 & 5.84 \mathrm{M} / \mathrm{min}\end{array}$

A) rate = k[NO]
B) rate = k[NO]²
C) rate = k[NO][H₂]
D) rate = k[NO]²[H₂]
E) rate = k[NO]²[H₂]²

Answer 2

B

Question 3

For the reaction A + 3B $\rarr$ 2C, the rate of disappearance of B given by ( $\Delta$ [B]/ $\Delta$ t) may also be expressed as

A)( $\Delta$ [B]/ $\Delta$ t) = - (1/3) $\Delta$ [A]/ $\Delta$ t.
B)( $\Delta$ [B]/ $\Delta$ t) = - 3 $\Delta$ [A]/ $\Delta$ t.
C)( $\Delta$ [B]/ $\Delta$ t) = 3 $\Delta$ [A]/ $\Delta$ t.
D)( $\Delta$ [B]/ $\Delta$ t) = (1/3) $\Delta$ [A]/ $\Delta$ t.
E)( $\Delta$ [B]/ $\Delta$ t) = - $\Delta$ [A]/ $\Delta$ t.

Answer 3

( $\Delta$ [B]/ $\Delta$ t) = 3 $\Delta$ [A]/ $\Delta$ t.

Question 4

Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO₂(aq) + 2OH^-(aq) $\rarr$ ClO₂^-(aq) + ClO₃^-(aq) + H₂O(l)
Under a certain set of conditions, the initial rate of disappearance of chlorine dioxide was determined to be 2.30 x 10^-1 M/s. What is the initial rate of appearance of chlorite ion under those same conditions

A) 5.75 x 10^-2 M/s
B) 1.15 x 10^-1 M/s
C) 2.30 x 10^-1 M/s
D) 4.60 x 10^-1 M/s
E) 9.20 x 10^-1 M/s

Question 5

Concerning the rate law, Rate = k[A]²[B], what are appropriate units for the rate constant k

A) s^-1
B) M^-1s^-1
C) M^-2s^-1
D) M/s
E) M²/s

Question 6

The reaction A + 2B $\rarr$ products has the rate law, rate = k[A][B]³. If the concentration of B is doubled while that of A is unchanged, by what factor will the rate of reaction increase

A) 2
B) 4
C) 6
D) 8
E) 9

Question 7

For the overall chemical reaction shown below, which one of the following statements can be rightly assumed
2H₂S(g) + O₂(g) $\rarr$ 2S(s) + 2H₂O(l)

A) The reaction is third-order overall.
B) The reaction is second-order overall.
C) The rate law is, rate = k[H₂S]² [O₂].
D) The rate law is, rate = k[H₂S] [O₂].
E) The rate law cannot be determined from the information given.

Question 8

The reaction A + 2B $\rarr$ products was found to have the rate law, rate = k[A] [B]². Predict by what factor the rate of reaction will increase when the concentration of A is doubled and the concentration of B is also doubled.

A) 2
B) 4
C) 6
D) 8
E) 9

Question 9

Concerning the rate law, Rate = k[A]⁰, what are appropriate units for the rate constant k

A) s^-1
B) M^-1s^-1
C) M^-2s^-1
D) M/s
E) M²/s

Question 10

For the reaction BrO₃^- + 5Br^-+ 6H⁺ $\rarr$ 3Br₂ + 3H₂O at a particular time, - $\Delta$ [BrO₃^-]/ $\Delta$ t = 1.5 * 10^-2 M/s. What is - $\Delta$ [Br^-]/ $\Delta$ t at the same instant

A) 13 M/s
B) 7.5 * 10^-2 M/s
C) 1.5 * 10^-2 M/s
D) 3.0 * 10^-3 M/s
E) 330 M/s

Question 11

Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO₂(aq) + 2OH^-(aq) $\rarr$ ClO₂^-(aq) + ClO₃^-(aq) + H₂O(l)
A kinetic study of this reaction under a certain set of conditions yielded the data below. $\begin{array}{|l|c|c|c|}\hline \operatorname{Exp} & {\left[\mathrm{ClO}_{2}\right](\mathrm{M})} & {\left[\mathrm{OH}^{-}\right](\mathrm{M})} & -\Delta\left[\mathrm{ClO}_{2}\right] / \Delta \mathrm{t}(\mathrm{M} / \mathrm{s}) \\\hline 1 & 0.0500 & 0.100 & 5.75 \times 10^{-2} \\\hline 2 & 0.100 & 0.100 & 2.30 \times 10^{-1} \\\hline 3 & 0.100 & 0.0500 & 1.15 \times 10^{-1} \\\hline\end{array}$ Which one of the following is the rate law for this reaction

A) rate = k[ClO₂][OH^-]
B) rate = k[ClO₂]²[OH^-]
C) rate = k[ClO₂][OH^-]²
D) rate = k[ClO₂]²[OH^-]²
E) rate = k[ClO₂]⁴[OH^-]

Question 12

Appropriate units for a first-order rate constant are

A) M/s.
B) 1/M·s.
C) 1/s.
D) 1/M²·s.

Question 13

It takes 42.0 min for the concentration of a reactant in a first-order reaction to drop from 0.45 M to 0.32 M at 25 ^$\circ$ C. How long will it take for the reaction to be 90% complete

A) 13.0 min
B) 86.0 min
C) 137 min
D) 222 min
E) 284 min

Question 14

For the reaction C₆H₁₄(g) $\rarr$ C₆H₆(g) + 4H₂(g), $\Delta$ P(H₂)/ $\Delta$ t was found to be 2.5 * 10^-2 atm/s, where $\Delta$ P(H₂) is the change in pressure of hydrogen. Determine $\Delta$ P(C₆H₁₄)/ $\Delta$ t for this reaction at the same time.

A) 2.5 * 10^-2 atm/s
B) -6.2 * 10^-3 atm/s
C) -2.5 * 10^-2 atm/s
D) 0.10 atm/s
E) 6.2 * 10^-3 atm/s

Question 15

For the hypothetical reaction A + 3B $\rarr$ 2C, the rate of appearance of C given by ( $\Delta$ [C]/ $\Delta$ t) may also be expressed as

A)( $\Delta$ [C]/ $\Delta$ t) = $\Delta$ [A]/ $\Delta$ t
B)( $\Delta$ [C]/ $\Delta$ t) = -(3/2) $\Delta$ [B]/ $\Delta$ t
C)( $\Delta$ [C]/ $\Delta$ t) = -(2/3) $\Delta$ [B]/ $\Delta$ t
D)( $\Delta$ [C]/ $\Delta$ t) = -(1/2) $\Delta$ [A]/ $\Delta$ t

Question 16

Concerning the rate law, Rate = k[A][B], what are appropriate units for the rate constant k

A) s^-1
B) M^-1s^-1
C) M^-2s^-1
D) M/s
E) M²/s

Question 17

The reaction A + 2B $\rarr$ products has been found to have the rate law, rate = k[A] [B]². While holding the concentration of A constant, the concentration of B is increased from x to 3x. Predict by what factor the rate of reaction increases.

A) 3
B) 6
C) 9
D) 27
E) 30

Question 18

Concerning the rate law, Rate = k[A][B][C], what are appropriate units for the rate constant k

A) s^-1
B) M^-1s^-1
C) M^-2s^-1
D) M/s
E) M²/s

Question 19

Nitric oxide gas (NO) reacts with chlorine gas according to the chemical equation given below.NO + 1/2Cl₂ $\rarr$ NOCl
The following initial rates of reaction have been measured for the given reagent concentrations. $\begin{array}{lccc} Expt.\# & Rate (M/hr) & NO (M) & \mathrm{Cl}_{2}(\mathrm{M}) \\\hline1 & 1.19 & 0.50 & 0.50 \\2 & 4.79 & 1.00 & 0.50 \\3 & 9.59 & 1.00 & 1.00 \\\end{array}$ Which of the following is the rate law (rate equation) for this reaction

A) rate = k[NO]
B) rate = k[NO][Cl₂]^1/2
C) rate = k[NO][Cl₂]
D) rate = k[NO]²[Cl₂]
E) rate = k[NO]²[Cl₂]²

Question 20

The reaction A + 2B $\rarr$ products was found to follow the rate law: rate = k[A]²[B]. Predict by what factor the rate of reaction will increase when the concentration of A is doubled, the concentration of B is tripled, and the temperature remains constant.

A) 5
B) 6
C) 12
D) 18
E) None of these.

Question 21

The half life for a first order reaction is 45 min. What is the rate constant in units of s^-1

A) 0.015 s^-1
B) 65 s^-1
C) 2.6 x 10^-4 s^-1
D) 3.9 x 10³ s^-1
E) 1.9 x 10³ s^-1

Question 22

A reaction was experimentally determined to follow the rate law, Rate = k[A]² where k = 0.456 s^-1M^-1. Starting with [A]_o = 0.500 M, how many seconds will it take for [A]_t = 0.250 M

A) 2.85 x 10^-2 s
B) 1.14 x 10^-1 s
C) 1.52 s
D) 4.39 s
E) 5.48x10^-1 s

Question 23

The following initial rate data apply to the reaction below.F₂(g) + 2Cl₂O(g) $\rarr$ 2FClO₂(g) + Cl₂(g) $\begin{array}{lccc}\mathrm{Expt.\#} & \left[\mathrm{F}_{2}\right](\mathrm{M}) & \left[\mathrm{Cl}_{2} \mathrm{O}\right](\mathrm{M}) & \mathrm{Initial~ rate} (\mathrm{M} / \mathrm{s}) \\\hline1 & 0.05 & 0.010 & 5.0 \times 10^{-4} \\2 & 0.05 & 0.040 & 2.0 \times 10^{-3} \\3 & 0.10 & 0.010 & 1.0 \times 10^{-3} \\\end{array}$ Which of the following is the rate law (rate equation) for this reaction

A) rate = k[F₂]²[Cl₂O]⁴
B) rate = k[F₂]²[Cl₂O]
C) rate = k[F₂][Cl₂O]
D) rate = k[F₂][Cl₂O]²
E) rate = k[F₂]²[Cl₂O]²

Question 24

A reaction was experimentally determined to follow the rate law, Rate = k[A] where k = 0.15 s^-1. Starting with [A]_o = 0.225M, how many seconds will it take for [A]_t = 0.0350M

A) 3.4 x 10^-2 s
B) 5.3 x 10^-3 s
C) 12 s
D) 160 s
E) 1.3 s

Question 25

The isomerization of cyclopropane to form propene is a first-order reaction. At 760 K, 15% of a sample of cyclopropane changes to propene in 6.8 min. What is the half-life of cyclopropane at 760 K

A) 3.4 * 10^-2 min
B) 2.5 min
C) 23 min
D) 29 min
E) 230 min

Question 26

At 700 K, the rate constant for the following reaction is 6.2 * 10^-4 min^-1. How many minutes are required for 20% of a sample of cyclopropane to isomerize to propene

A) 1,120 min
B) 360 min
C) 3710 min
D) 1.4 * 10^-4 min
E) 280 min

Question 27

A certain reaction, reaction A $\rarr$ products, is first order with respect toA. Starting with [A] = 0.250M, it takes 45 min to reduce the concentration of A to 0.110M. What is its rate constant for this reaction

A) 7.9 x 10^-3 min^-1
B) 1.1 x 10^-1 min^-1
C) 3.0 x 10^-4 min^-1
D) 1.8 x 10^-2 min^-1

Question 28

A city's water supply is contaminated with a toxin at a concentration of 0.63 mg/L. For the water to be safe for drinking, the concentration of this toxin must be below 1.5 x 10^-3 mg/L. Fortunately, this toxin decomposes to a safe mixture of products by first-order kinetics with a rate constant of 0.27 day^-1. How long will it take for the water to be safe to drink

A) 2.2 days
B) 2.6 days
C) 20 days
D) 22 days
E) 27 days

Question 29

The half life for a first order reaction is 27 min. How long will it take for 4 half lives to occur

A) 53,000 min
B) 108 min
C) 81 min
D) 260 min
E) Not enough information given

Question 30

Ammonium ion (NH₄⁺) reacts with nitrite ion (NO₂^-) to yield nitrogen gas and liquid water. The following initial rates of reaction have been measured for the given reactant concentrations. $\begin{array}{lccc}\text { Expt. \# } & {\left[\mathrm{NH}_{4}{ }^{+}\right]} & {\left[\mathrm{NO}_{2}{ }^{-}\right]} & \text {Initial rate }(\mathrm{M} / \mathrm{hr}) \\\hline 1 & 0.010 & 0.020 & 0.020 \\2 & 0.015 & 0.020 & 0.030 \\3 & 0.030 & 0.010 & 0.015\end{array}$ Which of the following is the rate law (rate equation) for this reaction

A) rate = k [NH₄⁺] [NO₂^-]⁴
B) rate = k [NH₄⁺] [NO₂^-]
C) rate = k [NH₄⁺] [NO₂^-]²
D) rate = k [NH₄⁺]² [NO₂^-]
E) rate = k [NH₄⁺]^1/2 [NO₂^-]^1/4

Question 31

The isomerization of cyclopropane to propene follows first-order kinetics. At 700 K, the rate constant for this reaction is 6.2 * 10^-4 min^-1. How many minutes are required for 10.0% of a sample of cyclopropane to isomerize to propene

A) 16,100 min
B) 170 min
C) 3,710 min
D) 1.43 * 10^-3 min
E) 1,120 min

Question 32

Appropriate units for a second-order rate constant are

A) M/s
B) 1/M·s
C) 1/s
D) 1/M²·s

Question 33

The data below were determined for the reaction shown below.S₂O₈^2- + 3I ^- (aq) $\rarr$ 2SO₄^2- + I₃^-

$\begin{array}{lccc}\text { Expt. \# } & \left[\mathrm{S}_{2-} \mathrm{O}_{8}{ }^{2}\right] & {[I-]} & \text { Initial Rate } \\\hline 1 & 0.038 & 0.060 & 1.4 \times 10^{-5} \mathrm{M} / \mathrm{s} \\2 & 0.076 & 0.060 & 2.8 \times 10^{-5} \mathrm{M} / \mathrm{s} \\3 & 0.076 & 0.030 & 1.4 \times 10^{-5} \mathrm{M} / \mathrm{s}\end{array}$ The rate law for this reaction must be:

A) rate = k[S₂O₈^2- ][I ^-]³
B) rate = k[S₂O₈^2-]
C) rate = k[S₂O₈^2-]²[I ^-]²
D) rate = k[I ^-]
E) rate = k[S₂O₈^2-][I ^-]

Question 34

Benzoyl chloride, C₆H₅COCl, reacts with water to form benzoic acid, C₆H₅COOH, and hydrochloric acid. This first-order reaction is 25% complete after 26 s. How much longer would one have to wait in order to obtain 99% conversion of benzoyl chloride to benzoic acid

A) 393 s
B) 419 s
C) 183 s
D) 293 s
E) 209 s

Question 35

Nitric oxide reacts with chlorine to form nitrosyl chloride, NOCl. Use the following data to determine the rate equation for the reaction.NO + ¹/₂Cl₂ $\rarr$ NOCl $\begin{array}{llll}\text { Expt. \# } & [\mathrm{NO}] & {\left[\mathrm{Cl}_{2}\right]} & {\text { Initial Rate }} \\\hline 1 & 0.22 & 0.065 & 0.96 \mathrm{M} / \mathrm{min} \\2 & 0.66 & 0.065 & 8.6 \mathrm{M} / \mathrm{min} \\3 & 0.44 & 0.032 & 1.9 \mathrm{M} / \mathrm{min}\end{array}$

A) rate = k[NO]
B) rate = k[NO][Cl₂]^1/2
C) rate = k[NO][Cl₂]
D) rate = k[NO]²[Cl₂]
E) rate = k[NO]²[Cl₂]²

Question 36

A city's water supply is contaminated with a toxin at a concentration of 0.63 mg/L. Fortunately, this toxin decomposes to a safe mixture of products by first-order kinetics with a rate constant of 0.27 day^-1. How long will it take for half of the toxin to decompose

A) 0.17 days
B) 0.27 days
C) 0.38 days
D) 2.3 days
E) 2.6 days

Question 37

The isomerization of cyclopropane to form propene is a first-order reaction. At 760 K, 85% of a sample of cyclopropane changes to propene in 79.0 min. Determine the rate constant for this reaction at 760 K.

A) 3.66 * 10^-2 min^-1
B) 1.04 * 10^-2 min^-1
C) 2.42 min^-1
D) 2.06 * 10^-3 min^-1
E) 2.40 * 10^-2 min^-1

Question 38

aa

Question 39

The first-order decomposition, A $\rarr$ products, has a rate constant of 0.150 s^-1. Starting with [A]_o = 0.350 M, how much time is required for [A]_t = 0.125 M

A) 6.86 s
B) 2.98 s
C) 34 s
D) 1.50 s
E) 4.62 s

Question 40

At 25 ^$\circ$ C the rate constant for the first-order decomposition of a pesticide solution is 6.40 *10^-3 min^-1. If the starting concentration of pesticide is 0.0314 M, what concentration will remain after 62.0 min at 25 ^$\circ$ C

A) 1.14 * 10^-1 M
B) 47.4 M
C) -8.72.0 M
D) 2.11 * 10^-2 M
E) 2.68* 10^-2 M

Question 41

A certain first-order reaction A $\rarr$ B is 25% complete in 42 min at 25 ^$\circ$ C. What is the half-life of the reaction

A) 21 min
B) 42 min
C) 84 min
D) 20 min
E) 101 min

Question 42

For what order reaction does the half-life get longer as the initial concentration increases

A) zero order
B) first order
C) second order
D) none of them because half-life is always independent of the initial concentration

Question 43

A reaction is experimentally found to follow the rate law, Rate = k[A]² where k = 0.130 M^-1min^-1. Starting with [A]_o = 2.50 M, how many seconds will it take for [A]_t = 1.25 M

A) 3.08 s
B) 185 s
C) 5.33 s

Question 44

The reaction 2NO₂(g) $\rarr$ 2NO(g) + O₂(g) is suspected to be second order in NO₂. Which of the following kinetic plots would be the most useful to confirm whether or not the reaction is second order

A) A plot of [NO₂]^-1 vs. t
B) A plot of ln [NO₂]^-1 vs. t
C) A plot of ln [NO₂] vs. t
D) A plot of [NO₂]² vs. t
E) A plot of [NO₂] vs. t

Question 45

In general, to calculate the rate constant for a second order reaction with respect to A, given an initial and final concentration as well as the time required for this change, which equation should be used

A) ln([A]_t/[A]_o) = - kt
B) t_1/2 = ln2/k
C) [A]_t = -kt + [A]_o
D) 1/[A]_t = kt + 1/[A]_o
E) Rate = k[A]

Question 46

The thermal decomposition of acetaldehyde, CH₃CHO $\rarr$ CH₄ + CO, is a second-order reaction. The following data were obtained at 518 ^$\circ$ C. $\begin{array}{cc}\text { Time, } \mathrm{s} & \text { Pressure } \mathrm{CH}_{3} \mathrm{CHO}, \mathrm{mmHg} \\\hline0 & 364 \\42 & 330 \\105 & 290 \\720 & 132\end{array}$ Based on the data given, what is the half-life for the disappearance of acetaldehyde

A) 1.5 * 10⁵ s
B) 410 s
C) 5.4 * 10⁷ s
D) 520 s
E) 305 s

Question 47

Concerning the decomposition of A, A $\rarr$ products, which of the following methods could be used to determine the order of the reaction with respect to A
I. Plot [A] vs time, ln[A] vs time, and 1/[A] vs time and identify which plot yields a straight line.
II. Vary the concentration of A and note by what factor the rate changes.
III. Identify if successive half lives of A double, halve, or stay constant.

A) I only
B) II only
C) III only
D) I and III
E) I, II, and III

Question 48

For the chemical reaction A $\rarr$ B + C, a plot of [A]_t versus time is found to give a straight line with a negative slope. What is the order of reaction with respect to A

A) zero
B) first
C) second
D) third
E) Such a plot cannot reveal the order of the reaction.

Question 49

For a second order reaction, the half-life is equal to

A) t_1/2 = 0.693/k.
B) t_1/2 = k/0.693.
C) t_1/2 = 1/k[A]_o.
D) t_1/2 = k.
E) t_1/2 = [A]_o/2k.

Question 50

Which one of the following changes would alter the rate constant (k) for the reaction 2A + B $\rarr$ products

A) increasing the concentration of A
B) increasing the concentration of B
C) increasing the temperature
D) measuring k again after the reaction has run for a while

Question 51

A certain reaction A $\rarr$ products is second order with respect toA. If it takes 45 min to reduce the concentration of A from 0.350 M to 0.125 M, what is the rate constant for this reaction

A) 3.8 x 10^-4 M^-1min^-1
B) 1.9 x 10^-3 M^-1min^-1
C) 5.0 x 10^-3 M^-1min^-1
D) 2.3 x 10^-2 M^-1min^-1
E) 1.1 x 10^-1 M^-1min^-1

Question 52

The graphs below all refer to the same reaction. What is the order of this reaction

A) zero order
B) first order
C) second order
D) unable to predict

Question 53

For the reaction X + Y $\rarr$ Z, the reaction rate is found to depend only upon the concentration of X. A plot of 1/X verses time gives a straight line. What is the rate law for this reaction

A) rate = k [X]
B) rate = k [X]²
C) rate = k [X][Y]
D) rate = k [X]²[Y]

Question 54

The thermal decomposition of acetaldehyde, CH₃CHO $\rarr$ CH₄ + CO, is a second-order reaction. The following data were obtained at 518 ^$\circ$ C. $\begin{array}{cc}\text { Time, } \mathrm{s} & \text { Pressure } \mathrm{CH}_{3} \mathrm{CHO}, \mathrm{mmHg} \\\hline0 & 364 \\42 & 330 \\105 & 290 \\720 & 132\end{array}$ Calculate the rate constant for the decomposition of acetaldehyde from the above data.

A) 2.2 * 10^-3/s
B) 0.70 mmHg/s
C) 2.2 * 10^-3/mmHg·s
D) 6.7 *10^-6/mmHg·s
E) 5.2 * 10^-5/mmHg·s

Question 55

At 25 ^$\circ$ C, the second-order reaction NOCl(g) $\rarr$ NO(g) + ¹/₂Cl₂(g)is 50% complete after 5.82 hours when the initial concentration of NOCl is 4.46 mol/L. How long will it take for the reaction to be 75% complete

A) 8.22 hr
B) 11.6 hr
C) 15.5 hr
D) 17.5 hr
E) 23.0 hr

Question 56

A reaction is experimentally found to follow the rate law, Rate = k[A]² where k = 0.355 M^-1min^-1. Starting with [A]_o = 1.55 M, how many seconds will it take for [A]_t = 0.150M

A) 6.58 s
B) 395 s
C) 6.02 s
D) 17.0 s
E) 1.02 x 10³ s

Question 57

For the chemical reaction A $\rarr$ C, a plot of 1/[A]_t versus time was found to give a straight line with a positive slope. What is the order of reaction

A) zeroth
B) first
C) second
D) Such a plot cannot reveal the order of the reaction.

Question 58

In general, to calculate the rate constant for a first order decomposition reaction, A $\rarr$ products, given the time needed to decrease the initial concentration by one half, which equation should be used

A) t_1/2 = 1/(k[A]_o)
B) t_1/2 = ln2/k
C) [A]_t = -kt + [A]_o
D) 1/[A]_t = kt + 1/[A]_o
E) Rate = k[A]

Question 59

In general, to calculate the time required for a given initial concentration to decrease by 35% given the rate constant with units of 1/M^-1s^-1, which equation should be used

A) ln([A]_t/[A]_o) = - kt
B) t_1/2 = ln2/k
C) [A]_t = -kt + [A]_o
D) 1/[A]_t = kt + 1/[A]_o
E) Rate = k[A]

Question 60

A certain reaction A $\rarr$ products is second order with respect to A with a rate constant, k, 0.122 M^-1min^-1. Starting with [A]_o = 1.01M, how many seconds will it take for A to reach a concentration of 0.750M

A) 2.81 s
B) 14.9 s
C) 893 s
D) 169 s
E) 128 s

Question 61

In general, to calculate the activation energy for an elementary step given the rate constants at two different temperatures, which equation should be used

A) ln([A]_t/[A]_o) = - kt
B) t_1/2 = ln2/k
C) ln(k₁/k₂) = E_a/R((T₁ - T₂)/T₁T₂)
D) 1/[A]_t = kt + 1/[A]_o
E) Rate = k[A]

Question 62

Calculate the activation energy, in kJ/mol, for the redox reaction Sn²⁺ + 2Co³⁺ $\rarr$ Sn⁴⁺ + 2Co²⁺. $\begin{array}{cc}\operatorname{Temp}\left({ }^{\circ} \mathrm{C}\right) & \mathrm{k}(1 / \mathrm{M} \cdot \mathrm{~s})\\\hline2 & 3.12 \times 10^{3} \\27 & 27.0 \times 10^{3}\end{array}$

A) 59.2
B) 0.477
C) 5.37
D) 163 kJ
E) 48.1 kJ

Question 63

According to the collision theory, all collisions do not lead to reaction. Which choice gives both reasons why not all collisions between reactant molecules lead to reaction
1. The total energy of two colliding molecules is less than some minimum amount of energy.
2. Molecules cannot react with each other unless a catalyst is present.
3. Molecules that are improperly oriented during collision will not react.
4. Solids cannot react with gases.

A) 1 and 2
B) 1 and 3
C) 1 and 4
D) 2 and 3
E) 3 and 4

Question 64

The activation energy for the following first-order reaction is 102 kJ/mol.N₂O₅(g) $\rarr$ 2NO₂(g) + ¹/₂O₂(g) The value of the rate constant (k) is 1.35 * 10^-4 s^-1 at 35 ^$\circ$ C. What is the value of k at 0 ^$\circ$ C

A) 8.2 * 10^-7 s^-1
B) 1.9 * 10^-5 s^-1
C) 4.2 * 10^-5 s^-1
D) 2.2 * 10^-2 s^-1
E) none of these

Question 65

The reaction C₄H₁₀ $\rarr$ C₂H₆ + C₂H₄ has an activation energy (E_a) of 350 kJ/mol, and the E_a of the reverse reaction is 260 kJ/mol. Estimate $\Delta$ H, in kJ/mol, for the reaction as written above.

A) -90 kJ/mol
B) +90 kJ/mol
C) 350 kJ/mol
D) -610 kJ/mol
E) +610 kJ/mol

Question 66

An increase in the temperature of the reactants causes an increase in the rate of reaction. The best explanation for this behavior is that as the temperature increases,

A) the concentration of reactants increases.
B) the activation energy decreases.
C) the collision frequency increases.
D) the fraction of collisions with total kinetic energy greater than E_a increases.
E) the activation energy increases.

Question 67

For the chemical reaction system described by the diagram below, which statement is true If the E_a for the forward reaction is 25 kJ/mol and the enthalpy of reaction is -95 kJ/mol, what is E_a for the reverse reaction

A) 120 kJ/mol
B) 70 kJ/mol
C) 95 kJ/mol
D) 25 kJ/mol
E) -70 kJ/mol

Question 68

For the chemical reaction system described by the diagram below, which statement is true

A) The forward reaction is endothermic.
B) The activation energy for the forward reaction is greater than the activation energy for the reverse reaction.
C) At equilibrium, the activation energy for the forward reaction is equal to the activation energy for the reverse reaction.
D) The activation energy for the reverse reaction is greater than the activation energy for the forward reaction.
E) The reverse reaction is exothermic.

Question 69

Given that E_a for a certain biological reaction is 48 kJ/mol and that the rate constant is 2.5 *10^-2 s^-1 at 15 ^$\circ$ C, what is the rate constant at 37 ^$\circ$ C

A) 2.7 * 10^-2 s^-1
B) 2.5 * 10^-1 s^-1
C) 1.0 * 10^-1 s^-1
D) 6.0 * 10^-3 s^-1
E) 1.1 s^-1

Question 70

When the concentrations of reactant molecules are increased, the rate of reaction increases. The best explanation for this phenomenon is that as the reactant concentration increases,

A) the average kinetic energy of molecules increases.
B) the frequency of molecular collisions increases.
C) the rate constant increases.
D) the activation energy increases.
E) the order of reaction increases.

Question 71

The Arrhenius equation is k = Ae^-Ea/RT. The slope of a plot of ln k vs. 1/T is equal to

A) -k
B) k
C) E_a
D) -E_a /R
E) A

Question 72

The isomerization of methyl isocyanide, CH₃NC $\rarr$ CH₃CN, follows first-order kinetics. The half-lives were found to be 161 min at 199 ^$\circ$ C and 12.5 min at 230 ^$\circ$ C. Calculate the activation energy for this reaction.

A) 6.17 * 10^-3 kJ/mol
B) 31.4 kJ/mol
C) 78.2 kJ/mol
D) 124 kJ/mol
E) 163 kJ/mol

Question 73

The following mechanism has been suggested for the reaction: $\begin{array}{ll}\mathrm{H}_{2} \mathrm{O}_{2}+2 \mathrm{H}^{+}+2 \mathrm{I}^{-} \rightarrow \mathrm{I}_{2}+2 \mathrm{H}_{2} \mathrm{O} \\\mathrm{H}_{2} \mathrm{O}_{2}+\mathrm{I}^{-} \rightarrow \mathrm{HOI}+\mathrm{OH}^{-} & \mathrm{Slow}\\\mathrm{OH}^{-}+\mathrm{H}^{+} \rightarrow \mathrm{H}_{2} \mathrm{O} & \mathrm{Fast}\\\mathrm{HOI}+\mathrm{H}^{+}+\mathrm{I}^{-} \rightarrow \mathrm{I}_{2}+\mathrm{H}_{2} \mathrm{O}& \mathrm{Fast}\end{array}$ Identify all intermediates included in this mechanism.

A) H⁺ and I ^-
B) H⁺ and HOI
C) HOI and OH^-
D) H⁺ only
E) H₂O and OH^-

Question 74

The activation energy for the reaction O + O₃ $\rarr$ 2O₂ is 25 kJ/mol, and the enthalpy change is $\Delta$ H = -388 kJ/mol. What is the activation energy for the decomposition of O₂ by the reverse reaction

A) 413 kJ
B) 388 kJ
C) 363 kJ
D) 50 kJ
E) 25 kJ

Question 75

The activation energy for the following reaction is 60. kJ/mol.Sn²⁺ + 2Co³⁺ $\rarr$ Sn⁴⁺ + 2Co²⁺ By what factor (how many times) will the rate constant increase when the temperature is raised from 10 ^$\circ$ C to 28 ^$\circ$ C

A) 1.002
B) 4.6
C) 5.6
D) 2.8
E) 696

Question 76

What is the slope of an Arrhenius plot for the following reaction
2NOCl $\rarr$ 2NO + Cl₂


$\begin{array}{lc}\text { Temperature (K) } & \mathrm{k}(\mathrm{~L} / \mathrm{mol} \cdot \mathrm{~s})\\\hline400 . & 6.6 \times 10^{-4} \\500 . & 2.9 \times 10^{-1} \\600 . & 16.3\end{array}$

A) 8.18 * 10^-2 K
B) 5.06 * 10^-2 K
C) -1.22 * 10⁴ K
D) -1.96 * 10⁴ K
E) not enough information to calculate the slope

Question 77

If E_a for a certain biological reaction is 50. kJ/mol, by what factor (how many times) will the rate of this reaction increase when body temperature increases from 37 ^$\circ$ C (normal) to 40 ^$\circ$ C (fever)

A) 1.15
B) 1.20
C) 2.0 * 10⁵
D) 1.0002
E) 2.0

Question 78

At 25 ^$\circ$ C, by what factor is the reaction rate increased by a catalyst that reduces the activation energy of the reaction by 1.00 kJ/mol

A) 1.63
B) 123
C) 1.04
D) 1.50
E) 2.53

Question 79

The activation energy for the reaction CH₃CO $\rarr$ CH₃ + CO is 71 kJ/mol. How many times greater is the rate constant for this reaction at 170 ^$\circ$ C than at 150 ^$\circ$ C

A) 0.40
B) 1.1
C) 2.5
D) 4.0
E) 5.0

Question 80

At 30 ^$\circ$ C, by how much is a reaction's activation energy decreased by the addition of a catalyst if the catalyst triples the reaction rate

A) 2.77 kJ/mol
B) 274 J/mol
C) 2.70 J/mol
D) 119 J/mol
E) 1.20 kJ/mol