Experiment #2

Description

please only do the calculations part I have the two files you need one is the data and the other is the calculation part at the bottom

Unformatted Attachment Preview

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A
B
CLASS DATA
Room Temperature Runs
Uncatalyzed
RUN #
TIME (s)
1
45
2
84
3
228
4
296
5
49
6
83
7
196
8
326
C
D
45
115
167
331
43
114
162
272
Catalyzed
RUN #
9
10
11
12
27
62
73
102
TIME (s)
31
49
90
88
Temperature Dependent Runs
RUN #
TEMP (°C) TIME (s)
13
6.5
309
13
8.0
547
13
10.4
453
13
10.1
421
13
10.0
446
14
21.8
163
14
21.0
169
14
22.0
221
14
21.9
213
14
21.0
166
14
20.5
202
15
29.5
98
15
29.5
82
15
30.1
72
E
F
G
H
I
42
116
121
287
44
77
169
285
AVG (s)
44
105
172
305
45
91
176
294
STDEV
2
19
54
23
3
20
18
28
STDEV %
4%
18%
31%
8%
7%
22%
10%
9%
25
51
75
148
AVG (s)
28
54
79
113
STDEV
3
7
9
31
STDEV %
11%
13%
12%
28%
# of values
Q90%
Q95%
Q99%
3
0.941
0.97
0.994
Q = gap/range
RUN #
16
16
16
16
16
16
TEMP (°C)
39.5
39.5
38.0
37.9
39.1
40.9
page 1
TIME (s)
54
52
50
51.5
62
52
Q TEST TABLE
4
5
0.765
0.642
0.829
0.71
0.926
0.821
gap: different between outlier and
next closest value
range: different between highest value
and lowest value in series
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J
K
L
M
N
O
P
Q
DATA ANALYSIS
1) OUTLIERS
You cannot simply throw out data points that seem “off” without doing something called a Q-test. The Q-test will
let you know if an outlier can be thrown out. It should be used sparingly (only once per unique data set).
RUN #3
RUN #6
RUN #12
etc
228
114
148
TIME (s)
167
83
102
121
77
88
GAP
61
32
47
RANGE
107
37
60
Q CALC
0.570
0.858
0.775
THROW OUT?
No
No
No
2) delta[S2O82-] (see prelab #2a)
3) Calculate Ri and ki (Room Temperature Runs)
Uncatalyzed
RUN #
AVG TIME (s)
Ri (M s-1)
1
44
1.4E-05
2
105
6.0E-06
3
172
3.7E-06
4
305
2.1E-06
1.4E-05
5
45
6
91
6.9E-06
7
176
3.6E-06
8
294
2.1E-06
6.30E-04 input value here (no units)
V S2O82- (mL) V I- (mL)
8.00
4.00
4.00
4.00
2.00
4.00
1.00
4.00
4.00
8.00
4.00
4.00
4.00
2.00
4.00
1.00
[S2O82-]
[I-]
ki* (units)
8.4E-02
4.2E-02
4.0E-03
4.2E-02
4.2E-02
3.4E-03
2.1E-02
4.2E-02
4.1E-03
1.1E-02
4.2E-02
4.7E-03
4.2E-02
8.4E-02
3.9E-03
4.2E-02
4.2E-02
3.9E-03
4.2E-02
2.1E-02
4.0E-03
4.2E-02
1.1E-02
4.8E-03
4) AVERAGE
4.1E-03
Catalyzed
STDEV
0.000455
RUN #
AVG TIME (s)
Ri (M s-1)
V S2O82- (mL) V I- (mL)
[S2O82-]
[I-]
ki* (units)
9
31
2.0E-05
4.00
8.00
1.3E-03
8.4E-02
1.8E-01
10
49
1.3E-05
4.00
4.00
2.6E-03
4.2E-02
1.2E-01
11
90
7.0E-06
4.00
2.00
5.3E-03
2.1E-02
6.3E-02
12
88
7.2E-06
4.00
1.00
1.1E-02
1.1E-02
6.5E-02
*NOTE: You must calculate the rate order using the Method of Initial Rates before you can calculate ki. You must
do this in your lab notebook under “Calculations” – not in this spreadsheet.
page 2
R
S
T
U
1 DATA ANALYSIS
2
3 5) TEMPERATURE DEPENDENCE (ARRHENIUS PLOT)
4
RUN #
TIME (s)
Ri (M s-1)
V S2O82- (mL)
5
13
309
2.0E-06
2.00
6
13
547
1.2E-06
2.00
7
13
453
1.4E-06
2.00
8
13
421
1.5E-06
2.00
9
13
446
1.4E-06
2.00
10
14
3.9E-06
2.00
163
11
14
3.7E-06
2.00
169
12
14
2.9E-06
2.00
221
13
14
3.0E-06
2.00
213
14
14
3.8E-06
2.00
166
15
14
3.1E-06
2.00
202
16
15
98
6.5E-06
2.00
17
15
82
7.7E-06
2.00
18
15
72
8.8E-06
2.00
19
16
54
1.2E-05
2.00
20
16
52
1.2E-05
2.00
21
16
50
1.3E-05
2.00
22
16
51.5
1.2E-05
2.00
23
16
62
1.0E-05
2.00
24
16
52
1.2E-05
2.00
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39
40
V
W
X
Y
V I- (mL)
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
[S2O82-]
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
2.1E-02
[I-]
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
4.2E-02
ki* (units)
2.3E-03
1.3E-03
1.6E-03
1.7E-03
1.6E-03
4.4E-03
4.2E-03
3.2E-03
3.3E-03
4.3E-03
3.5E-03
7.3E-03
8.7E-03
9.9E-03
1.3E-02
1.4E-02
1.4E-02
1.4E-02
1.1E-02
1.4E-02
page 3
Z
AB
AC
DATA ANALYSIS
RUN #
TEMP (°C)
13
6.5
13
8.0
13
10.4
13
10.1
13
10.0
14
21.8
14
21.0
14
22.0
14
21.9
14
21.0
14
20.5
15
29.5
15
29.5
15
30.1
16
39.5
16
39.5
16
38.0
16
37.9
16
39.1
16
40.9
AD
AE
AF
AG
TEMP (K)
279.7
281.2
283.6
283.3
283.2
295.0
294.2
295.2
295.1
294.2
293.7
302.7
302.7
303.3
312.7
312.7
311.2
311.1
312.3
314.1
TEMP (1/K)
3.58E-03
3.56E-03
3.53E-03
3.53E-03
3.53E-03
3.39E-03
3.40E-03
3.39E-03
3.39E-03
3.40E-03
3.41E-03
3.30E-03
3.30E-03
3.30E-03
3.20E-03
3.20E-03
3.21E-03
3.21E-03
3.20E-03
3.18E-03
lnki
-6.07
-6.65
-6.46
-6.38
-6.44
-5.44
-5.47
-5.74
-5.70
-5.45
-5.65
-4.92
-4.75
-4.62
-4.33
-4.29
-4.25
-4.28
-4.47
-4.29
273.15
Arrhenius Plot
0.00
3.15E-03 3.20E-03 3.25E-03 3.30E-03 3.35E-03 3.40E-03 3.45E-03 3.50E-03 3.55E-03 3.60E-03
-1.00
-2.00
LnKI
AA
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-3.00
y = -6136.2x + 15.338
R² = 0.9496
-4.00
-5.00
-6.00
-7.00
(1/T)(1/k)
AH
Method of Initial Rates
CHEM 111BF – Experiment #2
Objective:
The method of initial rates will be used to determine the rate constant and rate law for
the reaction of the peroxydisulfate and iodide ions. Additionally, the effect of temperature
and the use of a catalyst will be examined.
Introduction:
The rate law for a reaction can be determined using the method of initial rates. In this
approach, several experimental runs are performed while keeping all concentrations
constant with exception to a single reactant. Examining the effect of the concentration
change on the rate of the reaction allows one to determine the order with respect to the
reactant. For example, if doubling the concentration quadruples the rate of the reaction,
the order of the reactant is taken to be two. Once the orders of the reactants are
determined, the known concentrations and measured rates may then be used to determine
the rate constant for the reaction. The rate of reaction for each run can be obtained by
measuring the time for each run to occur, where the rate of reaction is inversely related to
the time.
In this experiment, the rate constant and rate law will be determined for the reaction of
the peroxydisulfate (S2O82−) and iodide ions:
(1)
S2O82−(aq) + 2I−(aq) → 2SO42−(aq) + I2(aq)
For the above reaction, a generic rate law can be written as:
Rate = k [S2O82−]x[I−]y
Where:
k is the rate constant for reaction
x is the order of peroxydisulfate
y is the order of iodide
The iodine produced in this reaction immediately reacts with excess iodide to produce
the triiodide (I3−) ion:
(2)
I2(aq) + I−(aq) → I3−(aq)
Because the reactants in Reaction (1) form colorless solutions, an indicator must be added
to monitor the progress of the reaction. In the presence of starch, the triiodide ion will
produce a complex which appears dark-blue in aqueous solution, making it a great
indicator for this reaction. However, because this color change will occur immediately
upon the formation of the triiodide ion, it is necessary to add the thiosulfate ion (S2O32−).
The thiosulfate ion will react with the iodine as it is being formed in the reaction with
1
peroxydisulfate, preventing the immediate formation of triiodide and the production of the
starch/I3− complex:
(3)
2S2O32−(aq) + I2(aq) → S4O62−(aq) + 2I−(aq)
Because thiosulfate reacts quickly (and completely) with the iodine, the starch/I3−
complex will not form until the thiosulfate has been completely consumed. The addition of
the thiosulfate to the reaction mixture delays the formation of the dark-blue color, allowing
the reaction to be timed.
Temperature Effects
The rate constant for this reaction will be measured at several temperatures, allowing
for a determination of the activation energy and the frequency factor using the following
form of the Arrhenius equation:
Ln(k) = (−
E+ 1
– + Ln(A)
R T
In this equation:
k is the rate constant (units determined by the orders of the reactants)
Ea is the activation energy (in J/mol)
R is the universal gas constant (8.314 J/mol K)
T is the temperature (in kelvin)
A is the frequency factor (same units as for rate constant)
By plotting the natural logarithm of the rate constants versus the inverse of temperature
(in kelvin), a linear plot will be produced, where the slope and intercept provide the
activation energy and frequency factor, respectively.
Catalyst Effects
Copper(II) ions are known to catalyze the reaction between the peroxydisulfate and
iodide ions. It is likely that the positively-charged copper(II) ions have a greater affinity for
the negatively-charged iodide ions, thus lowering the activation energy of the reaction. The
reaction involves the reduction of the copper(II) ions in the presence of iodide ions, and the
regeneration of the copper(II) ions upon reaction of the copper(I) and peroxydisulfate ions.
Notice that the two steps show below add to yield Reaction (1) overall:
Step 1:
2Cu2+(aq) + 2I−(aq)
→
2Cu+(aq) + I2(aq)
Step 2:
2Cu+(aq) + S2O82−(aq)
→
2Cu2+(aq) + 2SO42−(aq)
Net:
S2O82−(aq) + 2I−(aq)
→
2SO42−(aq) + I2(aq)
2
v08112019a
Chemicals and Equipment:
0.20 M ammonium peroxydisulfate, (NH4)2S2O8
0.20 M ammonium sulfate, (NH4)2SO4
0.20 M potassium iodide, KI
0.20 M potassium nitrate, KNO3
0.012 M sodium thiosulfate, Na2S2O3
0.020 M copper(II) nitrate, Cu(NO3)2
0.2% starch solution
10-mL graduated pipets (6)
Small beakers (or flasks)
50-mL test tubes (2)
Water baths (3)
100 oC thermometer
Timer
Safety:
The chemicals used in this experiment are skin and eye irritants. Safety goggles should
be worn at all times while in the laboratory. Rinse your skin thoroughly in case of a spill
and wash your hands before leaving lab. Ammonium peroxydisulfate, potassium nitrate,
and copper(II) nitrate are oxidizing agents. Dispose of all chemicals in the provided waste
container.
Procedure:
You will be working with a partner for this experiment – be sure to record their name
into your laboratory notebook on each page that data is recorded. Together, you will form
a team that will be assigned only certain experimental runs. The data from each team will
be compiled to form the “Class Data”. Note that each team plays an important role in the
success of the experiment.
On the first day of the experiment, your team will complete an assigned set of
experimental runs. One person will mix the contents of the two reactions vessels (Vessels
A and B) while the other person uses a timer to record the time required for the dark-blue
color to appear. You will then switch roles and repeat the run, checking afterwards to see if
the times are within 10% of one another. If the runs are not within 10%, you and your
partner must both repeat the experimental run (until 10% agreement is achieved):
2
|Time #1 − Time #2|
= × 100 < 10% Average Time Use Table A, “Experimental Quantities”, to determine the correct amount of the chemical solutions needed for each run. Dispense only the amounts needed into labeled beakers (or flasks) and return to your work area. Note that you may always obtain additional chemical solutions, if needed, though any excess solution must be poured into the designated waste container. 3 v08112019a Next: 1. Label one small beaker as “Vessel A” and another as “Vessel B”. Make sure each beaker is both clean and dry before proceeding. 2. Pipet the amounts of each chemical solution as indicated in Table A, “Experimental Quantities”, into Vessel A. 3. Pipet the amounts of each chemical solution as indicated in Table A, “Experimental Quantities”, into Vessel B. You will quickly (but carefully!) mix the contents of the two vessels by repeatedly pouring the chemical solutions from one beaker into the other, back and forth about three times. Your partner should start the timer when the first drop from one vessel touches the chemical solution in the other vessel. Stop the timer at the first appearance of color, which signifies the formation of the starch/I3− complex. Record the temperature of the reaction mixture before disposing into a waste container. Room temperature runs (i.e., runs 1 through 12 and 14) can be performed without a water bath. However, runs 13, 15 and 16 will be performed at different temperatures, and will require the use of a water bath. For these runs, the chemical solutions will be placed into 50-mL test tubes, labeled as “Vessel A” and “Vessel B”. These test tubes will then need to be placed into water baths at the respective temperatures (as indicated on Table A, “Experimental Quantities”). Allow the test tubes (and chemical solutions) to reach thermal equilibrium with the water in the water bath before mixing. Upon mixing the contents of the test tubes and starting the timer, it will be necessary to place the test tube containing the mixture back into the water bath to maintain the temperature while waiting for the solution to change color. (The table of Experimental Quantities is found on the next page, pg. 5.) 4 v08112019a Experimental Quantities Vessel A Prepare this mixture by combining 1.0 mL starch, 2.0 mL of 0.012 M Na2S2O3 and the chemical solutions from columns 1 and 2 in Table A (below). Vessel B Prepare this mixture by combining the chemical solutions from columns 3 and 4 in Table A (below). Note: The total volume of Vessel A when prepared will be 11.0 mL, the total volume of Vessel B when prepared will be 8.0 mL, and the total volume of the prepared reaction mixture will be 19.0 mL. Table A: Experimental Quantities Column 1 Column 2 Run # 0.20 M KI 0.20 M KNO3 Volume (mL) Volume (mL) 1 4.0 4.0 2 4.0 4.0 3 4.0 4.0 4 4.0 4.0 5 8.0 0.0 6 4.0 4.0 7 2.0 6.0 8 1.0 7.0 9* 8.0 0.0 10* 4.0 4.0 11* 2.0 6.0 12* 1.0 7.0 13** (10 °C) 4.0 4.0 14** (RT) 4.0 4.0 15** (30 °C) 4.0 4.0 16** (40 °C) 4.0 4.0 Column 3 0.20 M (NH4)2S2O8 Volume (mL) 8.0 4.0 2.0 1.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 2.0 2.0 2.0 2.0 Column 4 0.20 M (NH4)2SO4 Volume (mL) 0.0 4.0 6.0 7.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 6.0 6.0 6.0 6.0 * For runs 9 – 12, add 1 drop of 0.020 M Cu(NO3)2 to Vessel B. ** For runs 13 – 16, be sure record the actual temperature of the reaction mixtures, rather than the temperature of the water bath. (RT = room temperature) 5 v08112019a Data: The data recorded should be recorded in a single table entitled “Team Data”. Suggested column headers are shown below: Team Data Run # Time #1 (s) Temp (oC) Time #2 (s) Temp (oC) Ave Time (s) % Difference On the second day of the experiment, the class data will be compiled in Excel. For each room temperature run (runs 1 – 12), calculate the class average time. The Instructor may provide information about how to identify outliers in the data set using a Q-test, before continuing with the analysis of the data. For the temperature-dependent runs (13 – 16), simply keep each team’s recorded temperature and time. Do not average the results of each run. Calculations and Results: If there is more than one calculation with the same formula then tabulate the results within a spreadsheet. However, you must show one calculation using data from a single run in your laboratory notebook. The plots for calculations #4, 5 and 8 should appear in the Results section. 1. Δ[S2O82−] – change in concentration of peroxydisulfate The change in concentration of peroxydisulfate (S2O82−) can be related to the change in concentration of the thiosulfate through stoichiometry. Additionally, because the same amount of thiosulfate (S2O32−) is used in every run, the change in concentration of thiosulfate is the same for all runs: (4) EH ∆[SE OEH G ] = −[SE OJ ]K × 1 mol IE 1 mol SE OEH G × EH 1 mol I 2 mol SE OJ E The initial concentration of thiosulfate ion is determined using the dilution equation: MP VP VR (5) [SE OEH J ]K = Where: Mc is the concentration of thiosulfate stock (0.012 M S2O32−) Vc is the volume of the thiosulfate stock used (2.0 mL) Vd is the total volume of the reaction solution (19.0 mL) 6 v08112019a 2. [S2O82−]0 and [I−]0 – initial concentrations of peroxydisulfate and iodide The stock solutions of peroxydisulfate and iodide are diluted upon mixing with the other reactants. The initial concentration of these reactants refers to the concentration after mixing, but before any reaction occurs. The volume of stock solution (Vc) used can be referenced in Table A, “Experimental Quantities”. (6) [SE OEH G ]K = (7) [I H ]K = (0.20 M)(? mL) MP VP = VR 19.0 mL (0.20 M)(? mL) MP VP = VR 19.0 mL The initial concentrations of the peroxydisulfate and iodide ions will be tabulated as described in Calculation #6 below. Only a single (sample) calculation for the peroxydisulfate and iodide ions should appear here. 3. Rn – rate of reaction, in terms of peroxydisulfate The rate of each reaction is calculated by dividing the change in concentration of peroxydisulfate (Δ[S2O82−]) by the average times for each run. Note the negative sign in the equation, as rates of reaction are, by definition, positive quantities. ∆[SE OEH G ] RV = − ∆t V (8) Where: Rn is the rate of run “n” (units of M s-1) Δtn is the average time of run “n” (units of s) n is the run number (1, 2, 3,… 16) The rates for all sixteen runs will be tabulated as described in Calculation #6 below. Only a single (sample) calculation should appear here. 4. x – order of the peroxydisulfate The order of the peroxydisulfate is determined using the method of initial rates using runs 1 – 4; runs where the peroxydisulfate concentration is varied and the iodide concentration is constant. Starting with the generic rate law for the reaction, we apply natural logarithm to both sides of the equality: 7 v08112019a X H Y R V = k[SE OEH G ] [I ] H Ln(R V ) = Ln(k) + x Ln([SE OEH G ]) + y Ln([I ]) Next, we group the terms which remain constant and rearrange the equation into the standard form for line (y = mx + b): (9) Ln(R V ) = x Ln([SE OEH G ]) + constant A plot of the natural logarithm of the rate versus the natural logarithm of the peroxydisulfate concentration for runs 1 – 4 will be linear, with slope equal to the order of the peroxydisulfate. Produce this plot using the calculated concentrations of peroxydisulfate and rates of reaction (Calculations #2 and 3, respectively). Be sure to label the axes, introduce a linear trendline, and show the equation of the best-fit line and square of the correlation coefficient (R2). 5. y – order of the iodide The order of the iodide is determined using the method of initial rates using runs 5 – 8; runs where the iodide concentration is varied and the peroxydisulfate concentration is constant. Similar to Calculation #4 above, a plot of the natural logarithm of the rate versus the natural logarithm of the iodide concentration for runs 5 – 8 will be linear, with slope equal to the order of the iodide. (10) Ln(R V ) = y Ln([IH ]) + constant Produce this plot using the calculated concentrations of iodide and rates of reaction (Calculations #2 and 3, respectively). Be sure to label the axes, introduce a linear trendline, and show the equation of the best-fit line and square of the correlation coefficient (R2). 6. kn – rate constant for each run “n” (Runs 1 – 8) The rate constant for each run can be determined using the initial concentrations of the reactants (Calculation #2), the rate of reaction for each run (Calculation #3) and orders of the reactants (Calculations #4 and 5): 8 v08112019a k= (11) Where: RV EH [SE OG ]XV [I H ]YV Rn is the rate for run “n” (units of M s-1) [S2O82−]n and [I−]n are the initial concentrations of the reactants for each run “n” (units of M) x and y are the orders of the reactants Calculate the rate constant for runs 1 – 8, and then determine the average and standard deviation of the rate constants. The average rate constant for runs 1 – 8 will be the reported as the room temperature rate constant for the reaction. Produce the following table, tabulating the results from Calculations #2, 3 and 6: Results Table #1: Runs 1 – 8 Run # Average Time (s) Rate (M s-1) Volumes Concentrations kn (units*) S2O82− (mL) I− (mL) [S2O82−] (M) [I−] (M) *The units for the rate constant must be determined from the orders of the reactants. Additionally, use the CTRL+~ function to produce a spreadsheet illustrating how the values in the above table were calculated. 7. Z – catalytic activity As can be seen in Table A, “Experimental Quantities”, with exception to the use of a catalyst, the experimental conditions are identical for runs 5 and 9, 6 and 10, 7 and 11, and 8 and 12. The ratio of the rates of reactions provides the factor (Z) by which the reaction rate is increased because of the catalyst: (12) _ = b ; ` bK = E ; d bb = J ; e bE = i ; G Calculate each of the factors, the average factor. Produce the following table, tabulating the factors: Z1 with run 9, Z2 with run 10, Z3 with run 11, and Z4 with run 12: Results Table #2: Runs 9 – 12 Run # Average Time (s) Rate (M s-1) Factor Associated with Catalyst (Z) 9 v08112019a Additionally, use the CTRL+~ function to produce a spreadsheet illustrating how the values in the above table were calculated. 8. kn – rate constant for each run “n” (Runs 13 – 16) Using the same approach as described in Calculation #6, determine the rate constants for each of the temperature-dependent runs (13 – 16). These rate constants will not be averaged with runs 1 – 8 but, rather, will be used to create an Arrhenius plot (see Calculation #9 below). Produce the following table, tabulating the results from Calculations #8: Results Table #3: Runs 13 – 16 Run # Temperature (oC) Temperature (K) 1/Temperature (1/K) kn (units*) Ln (kn) *The units for the rate constant must be determined from the orders of the reactants. Additionally, use the CTRL+~ function to produce a spreadsheet illustrating how the values in the above table were calculated. 9. Ea and A – activation energy and frequency factor The calculated rate constants and measured temperatures from runs 13 – 16 can be used to determine the activation energy and frequency factor for the reaction. To accomplish this, the Arrhenius equation will be used: Ln(k) = (− E+ 1 - + Ln(A) R T Produce an Arrhenius plot (Ln(k) vs. 1/T) using the values calculated in Calculation #8. Be sure to label the axes for the Arrhenius plot. Also, be sure to introduce a linear trendline, and show the equation of the best-fit line and square of the correlation coefficient (R2) for the Arrhenius plot. A plot of the natural log of the rate constants versus the inverse of temperatures (in kelvin) will produce a linear plot, with a slope and intercept equal to (−Ea/R) and Ln(A), respectively. Show the calculation of the activation energy, Ea, (units of kJ/mol) and the frequency factor, A, (same units as rate constant) following the presentation of the Arrhenius plot. 10 v08112019a The conclusion of this section should be a narrative that contains the determined rate law, average rate constant (with standard deviation) for room temperature, activation energy (in kJ/mol) and frequency factor, and average factor for catalytic activity (Z). Discussion: This section should contain a detailed discussion of the data and results with conclusions drawn wherever appropriate. ü Explain the expected observation for each of the following, then identify whether it was observed in your results: o Rate vs. concentration o Rate vs. temperature o Rate catalyzed vs. rate uncatalyzed ü Explain why thiosulfate was added and how the change in its concentration was used to find the rate of reaction (in terms of peroxydisulfate). ü Comment on the magnitude of the average rate constant for runs 1 – 12. Does this suggest that Reaction (1) is relatively fast or slow? Error Analysis: State the sources of errors which were inherent to the experiment (those beyond your control), and explain how they may have affected the final results. Possible sources of error could include a change in temperature during the reaction, lack of immediate color change, or incomplete mixing. 11 v08112019a Pre-Laboratory Assignment #2 Method of Initial Rates Name:______________________________ 1. A pair of students performed Runs 1 – 4 using the same quantities and concentrations as identified in Table A, “Experimental Quantities”. The average times for their runs below: Run # Average Team Time (s) 1 39 2 78 3 152 4 310 a. Using Calculation #1, Equation #4 on pg. 6, determine Δ[S2O82−]. b. Use Calculations #2 (Equation #6) and #3 (Equation #8) on pg. 7 to determine the concentrations of peroxydisulfate and rates of reaction, Rn, for runs #1 – 4, and record the values in the table below. Show a single (sample) calculation for each here: Rn: [S2O82−]: Run Rn (M s-1) [S2O82−] (M) [I−] (M) 1 0.042 2 0.042 3 0.042 4 0.042 12 v08112019a 2. Using the concentrations and rates of reaction calculated in Question #1b, complete the following table: Run Ln(Rn, M s-1) Ln([S2O82−], M) 1 2 3 4 Determine the order of the peroxydisulfate by plotting the natural logarithm of the rate versus the natural logarithm of the peroxydisulfate concentration. Be sure to label the axes, introduce a linear trendline, and show the equation of the best-fit line and square of the correlation coefficient (R2) – plot must be attached for credit. Order of peroxydisulfate: _________ (express as an integer) 3. Assuming the reaction is first-order with respect to iodide, and using the results from Questions #1 and #2, calculate the rate constant for the first run using Calculation #6 (Equation #11) on pg. 9. 4. A student mixed the solutions in Vessel A and Vessel B and waited the entire lab period but the mixture never changed to a dark blue color. What is the most likely mistake the student made? 5. A student mixed the solutions in Vessel A and Vessel B. Immediately, the solution turned blue. Identify a possible scenario for what might have happened. 13 v08112019a Purchase answer to see full attachment