Kinetics (II):

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Questions 1 through 3 are based on the following mechanism for the decomposition of hydrogen peroxide (H2O2) in the presence of the iodide ion (I-).

          step 1..... H2O2 +I-® H2O + OI-
          step 2..... H2O2 + OI-®H2O + O2 + I-
 1 The net or overall reaction is:

2H2O2®  2H2O + O2
H2O2®  H2 + O2
H2O2 + I- ® OI- + H2O 
H2O2 + OI- ® H2O + O2 + I-
H2O2 + I- ®2H + 2OI-

 2 The catalyst in the above mechanism is:

I-
H2O
OI-
O2
H2O2

 3 The intermediate in the above mechanism is:

I-
H2O 
OI-
O2
H2O2

Questions 4 and 5 are based on the following plots. 
Select the letter of the plot that best describes the relationships described below. 
All questions pertain to reactions of the type

A ® products. A plot may be used more than once in these questions.

Undisplayed Graphic

 4 A plot of average rate on the vertical axis versus the average concentration of Asquared on the horizontal axis for a secondorder reaction.

ABCDE

 5 A plot of the natural logarithm of the concentration of A on the vertical axis versus the time on the horizontal axis for a first order reaction.

ABCDE

 6 The age of a papyrus painting is determined by radiocarbon dating. A Geiger counter measures 7.70 counts per minute (c.p.m.) in a sample of the painting compared to 15.4 c.p.m. from carbon-14 in a living organism. If the half life is 5760 years, what is the age of the painting in years? The radioactive decay of carbon-14 follows first order kinetics.

332288057606641000 

Use the following information for questions 7 and 8.

The half life of a first order reaction of the type A ® products is 198s

 7 If the initial concentration of A is 4.00 M, how many seconds would be required for the concentration of A to drop to 0.50 M?

49.599.0396594792

 8 What is the rate of the reaction in mol A/Ls, when the concentration of A is 2.00 M?

1.01 x 10-2
2.50 x 10-2
3.50 x 10-3
5.00 x 10-3
7.00 x 10-3

 9 The following data were obtained at 25° C for the reaction
C2H5Br + OH- = C2H5OH + Br-
Determine the rate law for the reaction from these data.
 
[C2H5Br] [OH-] Rate
0.150 0.200 4.8 x 10-5
0.300 0.200 9.6 x 10-5
0.450 0.200 14.4 x 10-5
0.300 0.600 28.8 x 10-5

R = k[C2H5Br] 
R = k[C2H5Br]2
R = k[C2H5Br][OH-] 
R = k[C2H5Br]2[OH-] 
R = k[C2H5Br]2[OH-]3

 10 Which of the following is NOT a property of a catalyst?

It lowers the activation energy for both the forward and reverse processes.
It increases the rate of both the forward and reverse processes.
It may be recovered unchanged at the end of the reaction.
It increases the equilibrium constant.
It causes equilibrium to be reached more rapidly.

 11  The activation energy for a reaction may be obtained from a graph of:

logarithm of specific rate constant versus the reciprocal of absolute temperature.
specific rate constant versus absolute temperature.
specific rate constant versus concentration of reactant.
rate of reaction versus concentration of reactant.
logarithm of concentration of reactant versus time.

 12 The decomposition of benzene diazonium chloride follows first order kinetics: 
C6H5N2Cl (aq) ® C6H5Cl (l) + N2
The rate constant for this reaction is 0.105 s-1 at 10°C. Starting with a concentration of 0.066 M of C6H5N2Cl, calculate its concentration after 15 seconds. 

0.0083 M0.32 M5.3 x 10-7 M0.014 M0.037 M

 13 The half-life of the radioactive isotope phosphorus-32 is 14.3 days. How many days does it take for a sample of phosphorus-32 to lose 75% of its radioactivity?

7.1514.328.625.019.1

 14 For the reaction A + B + C ® products, the following initial rate data were obtained: 
 

[A]
[B]
[C]		 Initial Rate 
(M.s-1)
0.050 0.050 0.10 1.1 x 10-3
0.050 0.10 0.10 4.4 x 10-3
0.10 0.050 0.10 1.1 x 10-3
0.10 0.050 0.30 3.3 x 10-3
What is the rate law for the reaction?

R = k[A][B][C] 
R = k[A]2[B] 
R = k[B][C]2
R = k[B]2[C] 
R = k[A][B][C]2

Use the following mechanism which has been proposed for the reaction of 
C4H9Br with OH- to answer questions 15 through 17.

        Step 1........ C4H9Br ®C4H9+ + Br- ........slow
        Step 2........ C4H9+ + OH- ®C4H9OH........ fast
 15 What is the rate law consistent with this mechanism?

R = k[C4H9Br][OH-] 
R = k[C4H9+][OH-] 
R = k[C4H9Br] 
R = k[C4H9Br][OH-][Br-]-1
R = k[C4H9+]2

 16 Which one of the following is a reaction intermediate?

C4H9+
Br-
OH-
C4H9Br 
There is none.

 17 Which one of the following is a catalyst?

C4H9+
Br-
OH-
C4H9Br 
There is none.

Question 18 is based on the following information. 

The reaction between OCl- ions and I- ions in NaOH solution is given by the following equation: 
OCl-(aq) + I-(aq) ® OI-(aq) + Cl-(aq) 
The following initial rates of the reaction were measured at various
initial concentrations as recorded in the table below.


 

Experiment
[OCl-]0
[I-]0
[OH-]0		 Initial Rate
(M s-1)
1 0.0040 0.0020 1.00 4.8 x 10-4
2 0.0020 0.0040 1.00 4.8 x 10-4
3 0.0020 0.0020 1.00 2.4 x 10-4
4 0.0020 0.0020 0.50 4.8 x 10-4
5 0.0020 0.0020 0.25 9.6 x 10-4

 18 The rate law (or rate equation)is:

R = k[OCl-][I-][OH-]2
R = k[OCl-]2[I-][OH-] 
R = k[OCl-][I-][OH-]-1
R = k[OCl-]2[I-]-1[OH-] 
R = k[OCl-][I-][OH-] 

Questions 19 and 20 are based on the following information.

For a first order reaction the following data are obtained from an experiment by measuring the concentration as a function of time.  The reaction is of the type: A ® products.


 
time (secs.) [A]
0 1.00
50 0.500
100 ?

 19 Determine the molar concentration of A after 100 seconds have elapsed. 

0.5000.2500.3600.2000.000

 20 Determine the value of the rate constant, k(in sec-1)

1.4x10-2
50 
0.693 
100 
0.50

Questions 21 and 22 are based on the following:

The reduction of NO to N2 with H2;  2NO(g) + 2H2(g) = N2(g) + 2H2O(g) , is found to have the following experimentally determined rate equation:    Rate = k[NO]2[H2]

 21 What is the order of the reaction with respect to NO?

01-12-2

 22 If the concentration of NO and H2 were doubled then the rate of the reaction would:

Increase two fold 
Increase four fold 
Decrease two fold 
Decrease four fold 
Increase eight fold

Questions 23 and 24 are based on the following mechanism 
for the conversion of ozone to oxygen in the upper atmosphere.

          step 1. O3 + Cl ® O2 + OCl 
          step 2. O3 + OCl ® 2O2 + Cl
 23 The net or overall reaction is:

O3 + Cl ® O2 + OCl 
O3 + OCl ® 2O2 + Cl 
2O3® 3O2
3O2® 2O3
2O3 +Cl + OCl ® 3O2 + Cl + OCl

 24 The catalyst in the above mechanism is:

Cl 
OCl 
O3
O2
HCl