Name: Date:

CHE-112 —- CHAPTER 13 — PRACTICE QUESTIONS

1. Express the rate of the following reaction equation in terms of the rate of concentration change of NO2CI:

2 NO? (g) + Cl2 (g) ——+ 2 NO2Cl (g) A) rate of reaction = A[Cl2]/At

B) rate of reaction =— 4 (A[NO2CI]/Ap) C) rate of reaction= 4 (A[NO2CI]/Ar) D) rate of reaction =— 4 (A[NO2]/Ad)

2. Express the rate of the following reaction equation in terms of the rate of concentration change of CHCl:

CHC} (g) + Clo (g) ——+ CCl, (g) + HCl A) rate of reaction = A[CCl4]/At

B) rate of reaction = 2(A[CHC13]/At)

C) rate of reaction = A[CHCI3]/At

D) rate of reaction = —A[CHCl3]/At

3. Let the rate of the reaction described by the equation

H2 (g) + Bro (g) ——+ 2 HBr (g)

be expressed as —A[Br2]/Az. Express the rate of reaction in terms of the rate of concentration change of HBr.

A) rate of reaction =— % A[HBr]/At

B) rate of reaction = —A[H2]/At

C) rate of reaction = 4 A[HBr]/At D) rate of reaction = 2A[HBr]/At

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4. Let the rate of the reaction described by the equation

Ho (g) + 2 ICI (g) —— 2 HCl (g) + h (g)

be expressed as A[I2]/At. Express the rate of reaction in terms of the rate of concentration change of ICI.

A) rate of reaction = A[ICI]/At

B) rate of reaction =— % A[ICI]/At

C) rate of reaction =—A[ICI]/At

D) rate of reaction = —2A[ICI]/At

5. The rate law for the reaction described by the equation N20s (g) ——+ 2 NO» (g) + 4 O2 (g)

at 343 K is first order in [N2O5] with a rate constant k = 1.80 h"!. Given that [N2Os]o = 0.112 M, calculate the rate of the reaction at t= 0.

A) 0.112 Mh!

B) 0.202 M.h!

C) 1.80 M.h"!

D) 69.1 M.h"!

6. The rate law for the reaction described by the equation NOz (g) —-+ NO(g) + % Oz (g) at 598 K is:

rate of reaction = (0.54 M-!.s-!)[NO»]?

Given that [NO2]o = 8.33 - 10-7 M, calculate the rate of the reaction at t= 0s. A) 3.7:107 Ms! B) 8.3-10°7 Ms! C) 3.7-103 Ms"! D) 6.9-:103 Ms!

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7. The rate law for the reaction described by the equation CHC1 (g) + Cl2 (g) ——+ CCl (g) + HCl (g) is: rate of reaction = k[CHCI3][ Clo]! What is the overall order of this reaction? A) 1 B) 2 C) 3/2 D) 5/2 8. Nitrogen monoxide and oxygen react according to the reaction equation

2 NO (g) + O2 (g) ——+ 2 NO? (g)

Using the following initial rate data, determine the rate constant for the reaction.

Run [NO]o/M [O2]/M | Initial rate of formation of NO>(g)/MDs"! I 0.0228 0.0105 £35107 2 0.0456 0.0105 5.40: 10° 3 0.0228 0.0210 2.70: 10°

A) 2.47 M?.s!

B) 0.0564 M?.s"!

C) 1.35- 1073 M?.s! D) 1.23 M?.s"!

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2,

10.

ih,

I.

Hydrogen peroxide decomposes according to the reaction equation

2 H2O2 (aq) ——+ 2 H20 (J) + Op (g)

This reaction is first order in [H2O2] at 70°C with a rate constant of k = 0.0444 min“. If the initial concentration is [H202]o = 0.25 M, then what is the value of [H202] 45.0 minutes after the solution is prepared?

A) 0.0043 M

B) 0.035 M

C) 0.055 M

D) 0.15 M

Argon-41 is a y-emitter with a half-life of 109.2 minutes. What fraction of a sample of Ar- 41 remains after 37.5 hours?

A) 6.29- 1077

B) 7.70: 1077

C) 4.09- 10°

D) 6.92-10°°

If a sample of soditum-24 chloride contains 0.075 mg of sodium-24, how much sodium-24 remains after 9.63 hours? The half-life of sodium-24 is 14.96 hours.

A) 0.027 mg

B) 0.048 mg

C) 0.072 mg

D) 0.084 mg

You order a sample of Na3PO4 containing the radioisotope phosphorus-32 (¢1/2 = 14.28 days) on Monday. You don't get to it until Thursday, 3.0 days after it was prepared and shipped. How much of the activity remains in your sample?

A) 15%

B) 32%

C) 69%

D) 87%

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13.

14.

Is.

The gas-phase decomposition of CH3CHO (g) occurs according to the equation CH3CHO (g) ——+ CH4 (g) + CO (g)

The reaction is second order with k = 0.105 M~!.s"! at 490°C. If the concentration of CH3CHO (g) is 0.022 M initially, what will its concentration be 4.3 minutes later?

A) 0.0013 M

B) 0.0089 M

C) 0.014 M

D) 0.020 M

The rate law for the reaction described by the equation 2 N20 (g) ——+ 2 Nz (g) + O2 (g)

is second order in N20 (g). The reaction was carried out at 900 K with an initial concentration of N2O (g) of 3.5- 10-7 M. If it took 91.3 minutes for [N20] to fall to half it original value, what is the value of the rate constant for this reaction?

A) 3.5°107? M'st

B) 4.8: 10° M!. -

C) 5.2-103 Mls

D) 84-107? M!. é

The rate law for the reaction described by the equation

A (g) —~ B(g) + C(g)

is second order in A (g) with an rate constant k = 1.13 - 10°? M~!.s"! at 550 K. If the reaction is carried out at 550 K with an initial concentration of A (g) of 5.84 - 10° M, how long will it take for [A] to fall to half it original value?

A) 1450 seconds

B) 1520 seconds

C) 1600 seconds

D) 1920 seconds

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16. How does tripling the concentration of a reactant change the rate of a reaction that is second

17.

18.

19.

order in that reactant?

A) The rate increases by a factor of three: (3)!. B) The rate increases by a factor of six: (2)(3). C) The rate increases by a factor of eight: (2). D) The rate increases by a factor of nine: (3).

Cyclobutane, C4Hg (g), decomposes to ethylene, C2H4 (g), at 700 K: CaHs (g) ——+ 2 CoHa (g)

The reaction is first order in [C4Hg] with k = 0.015 min“!. If the initial concentration of C4Hs (g) is 1.33 M, what is its concentration after 5.5 minutes?

A) 0.36 M

B) 0.63 M

C) 0.98 M

D) 12M

How long does it take for the concentration of a reactant to decrease by 25.6% of its initial value for a first-order reaction with k= 1.35 min"!?

A) 13.18

B) 0.200 min

C) 1.01 min

D) 21.9s

If the half-life of uranium-238 is 4.47 - 10° years, then how long will it take for the amount of radioactivity in a sample to decrease to 0.050% of its original value?

A) 5.74 half-lives

B) 12.7 half-lives

C) 1.93-10!° years

D) 4.90- 10!° years

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20. Dinitrogen pentoxide decomposes according to the reaction equation

N2Os (g) ——+ 2 NO> (g) + % O2 (g)

If the initial concentration of N2Os (g) is [N2O5]o = 0.832 M, and if [N2Os5] = 0.166 M at ¢

= 65.0 min, then what is [NOz2] at t= 65.0 min? A) 0.525 M

B) 0.666 M

C) 1.05 M

D) 1.33 M

21. Incomplete initial rate data are given below for the reaction described by

22;

2 NO2 (g) ——> 2 NO (g) + O2 (g)

Run [NO2]o/M | (rate ofreaction)9/ MDs! 1 1.10 0.65 2 1.60 1.38 3 2:25 x

What is the rate of reaction, x, for Run 3? A) 1.53 M.s! B) 2.22 M.s"! C) 2.73 M.s"! D) 2.89 M.s"!

How does halving the concentration of a reactant change the rate of a reaction that is first order in that reactant?

A) The rate decreases by a factor of two: (1/2)!. B) The rate does not change: (1)!”.

C) The rate increases by a factor of 1.4: (2)!/. D) The rate increases by a factor of two: (2)!.

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23. If plotting your rate data as In[A] vs. ¢ results in a straight line, then which of the following represents the slope (m) of that line? A) -k B) In[{A]o C) 1/k D) 1/[A]o

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Answer Key - Chapter 13 Practice Problems

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