Time Resolved Pulsed Laser Photolysis Study of Pyrene Fluorescence Quenching by IAnion
Report by: Kelly Helfrich
Lab Team: Tim Haggerty, Kristen Woznick, Arjun Plakkat
The Pennsylvania State University, Department of Chemistry, CHEM 457, Section 1
Report Submitted: September 10, 2013
Abstract
In this experiment, varying concentrations of pyrene in a 50% ethanol-water solution is
fluoresced and quenched by the I- anion using laser photolysis. The main objective of the lab
was to measure the rate constants, of inherent fluorescence decay and of quenching by iodide
anion, of this reaction using nanosecond laser photolysis. The rate constant for spontaneous
fluorescence decay (ko) was determined to be (3.8 ± 0.9)*106 s-1 and the quenching rate constant
(kq) for the reaction of I- with excited pyrene was measured to be 125 ± 35.9 M-1 s-1.
Introduction
Fluorescence spectroscopy is a tool used to study the lifetime of a molecule in an excited
state. Molecules in an excited state exhibit different properties than in their ground state.1 In the
transition from a ground state to excited state, a molecule will promote an electron up to a higher
electron shell (one further from the nucleus). 2
Pyrene will promote an electron when a UV light with wavelength of 337 nm is pulsed at
the molecule with a nitrogen laser. Pyrene in its excited state has a higher reduction potential
than in its ground state due to the promotion of the electron.1
Pyrene Fluorescence Quenching by I- Anion
Helfrich 2
In general, aromatic compounds are much more stable than their alkane counterparts due
to the electron delocalization, or resonance forms it exhibits.3 Pyrene (Py) is a polycyclic
aromatic hydrocarbon (PAH);4 its chemical structure is shown below in Figure 1.
Figure 1: Chemical structure of Pyrene demonstrating aromaticity
As a stable PAH, Py in its ground state will not react with an electron donor in a redox reaction.4
In stark contrast, Pyrene in its excited state (*Py) is a good electron acceptor largely due to
conjugation. In the presence of an electron donor, such as I-, *Py will undergo a quenching
reaction to form Py- and an Iodine radical.1 Over time, *Py will relax back to its ground state
through both fluorescence of a photon and by radiationless decay from losing energy as heat.
The reaction mechanism is shown below in Figure 2.
Py + I- + hv1*Py (excitation from photons)
*Py + I-  Py- + I (quench of *Py)
*PyPy + hv2
(fluorescent decay of photon)
*PyPy + heat
(radiationless decay through loss of heat)
Figure 2: Reaction mechanism for excitation and decay of Pyrene through excitation from a
photon. The decay of *Py comes from a quenching mechanism, fluorescent decay, and loss of
heat.
Treating Py as a reactant and *Py as the product in the reaction Py + I-  Py*, the rate of
molecules relaxing from the excited to ground state can be written as the sum of the
concentration of the product times a constant, ko as shown in the following equation:
Pyrene Fluorescence Quenching by I- Anion
-d[*Py]/dt = ko[*Py]
Helfrich 3
(1)
If it is assumed that [*Py] is proportional to the intensity, I, equation one becomes
I=Io*exp(-kot)
(2)
Both of these equations use ko, which is the rate constant for the spontaneous decay of *Py.
When determining kq, we assume that since the concentration of the quencher is much larger
than the concentration of the pyrene, the rate constant will only depend on the concentration of
the quencher; therefore, the kinetics of the reaction can be considered pseudo-first order.1 The
equation for both spontaneous fluorescence and quenching can be written as follows:
-d[*Py]/dt = (ko + kq[I-])[*Py]
(3)
The term (ko + kq[I-]) is the combined rate constant for both spontaneous decay (ko) and the
pseudo-first order quenching (kq[I-]). The observed rate constant (kobs) can be determined from a
graph of the fluorescence emittance vs. time. The data will show exponential decay in the form
of y=a*exp(-kt) where k=kobs. A graph of kobs vs. [I-] will portray a linear relationship where ko
is the y-intercept and kq is the slope.1
Experimental
The complete experiment description can be found in the lab packet for CHEM 457
Experimental Physical Chemistry pages 5-5 to 5-7.1 In this experiment, a laser photolysis setup
is used as the primary apparatus. A diagram of the setup is shown below in Figure 3.
Pyrene Fluorescence Quenching by I- Anion
Helfrich 4
Figure 3: Laser photolysis setup to measure the emittance intensity in arbitrary units over time
with optical filter absorbing light below 350 nm
Five flasks containing varying concentrations of KI (0, 10, 20, 30, 40 mM) were analyzed
with the laser photolysis setup. The KI powder was measured to be 0.1659 g KI ± 0.0004 g to
create a 40 mM KI solution in 50% ethanol-water in a 10 mL ± 0.05 mL volumetric flask. A
serial dilution was performed from the 40 mM solution to form 30 mM (by transferring 3 mL of
the 40 mM flask to another 10 mL volumetric flask), 20 mM (by transferring 2 mL of the 40 mM
solution to a new 10 mL volumetric flask), and 10 mM (by transferring 1 mL of the 40 mM
solution to a new 10 mL volumetric flask) solutions. The solutions were then diluted with 50%
ethanol-water solution by filling to the 10 mL line on each flask.
The sample was place in a quartz cuvette and then purged for a minimum of five minutes
with nitrogen in order to remove any oxygen present in the solution. A needle was placed in the
cuvette with a glass stopper on top to create a seal. The apparatus used did not create a perfect
seal which could have let some oxygen into the sample. It is imperative that oxygen be purged
from the sample as it quenches pyrene fluorescence. After purging, the sample was placed in the
sample cell of the photolysis setup and the emission intensity was measured.
Results
The exponential decay data collected is depicted in the graph of Emission Intensity
(arbitrary units) vs. Time (ns) below in Figure 4. The best-fit exponential decay equations and
the R2 values are displayed on the graph and in the table in Figure 5.
Pyrene Fluorescence Quenching by I- Anion
Fluorescence Emmision Intensity (arbitrary
units)
0.63
0.59
0.55
0.51
0.47
0.43
0.39
0.35
0.31
0.27
0.23
0.19
0.15
0.11
0.07
0.03
-0.01
-75
-0.05
Helfrich 5
Fluorescence Decay of Excited Pyrene
via an I- Quench over Time 0 mM
0 mM: y = 0.6628e-0.003x
R² = 0.9975
10 mM: y = 0.7157e-0.006x
R² = 0.9803
20 mM: y = 0.5513e-0.007x
R² = 0.9768
30 mM: y = 0.6647e-0.009x
R² = 0.9735
40 mM: y = 0.5445e-0.008x
R² = 0.9659
10 mM
20 mM
30 mM
40 mM
Expon. (0 mM)
Expon. (10 mM)
Expon. (20 mM)
Expon. (30 mM)
Expon. (40 mM)
50
175
300 425 550
Time (ns)
675
800
925
Figure 4: Plot of Fluorescence Decay (arbitrary units) over Time (ns). The exponential best-fit
equations and R-squared values for each concentration of KI are expressed on the graph. The
coefficient of x serves as the negative kobs value.
[I-]
(mM)
Uncertainty of
[I-]
R2(linear ln
graph)
0
0
0.999
10
2.24*10-4
0.9989
20
4.48*10-4
0.9980
30
6.72*10-4
0.9984
40
8.96*10-4
0.9984
Figure 5: Table relating [I-] to the exponential decay and R-squared values. As the [I-]
increases, the R-squared value for the exponential decay decreases.
Regression analysis was performed in Excel. Excel is able to fit linear regressions with
much more accuracy than it can exponential best-fit equations. In order to obtain better data, the
linear relationship of the natural log of emittance intensity vs. time is graphed in Figure 6 below.
Pyrene Fluorescence Quenching by I- Anion
Helfrich 6
This graph provides more accurate kobs values represented as the negative slope of each linear
best-fit line.
ln(Emmittance Intensity) vs. Time for the Fluorescence Decay of
Excited Pyrene in the Presence of I-
0
ln(Emittance Intensity) (arbitrary units)
0
100
200
300
400
600
700
0 mM
-0.5
-1
500
0 mM: y = -0.0033x - 0.4374
R² = 0.999
10 mM: y = -0.005x - 0.5181
R² = 0.9989
20 mM: y = -0.0069x - 0.61
R² = 0.998
-1.5
30 mM: y = -0.0089x - 0.4483
R² = 0.9984
-2
10 mM
20 mM
30 mM
40 mM
Linear (0 mM)
Linear (10 mM)
-2.5
40 mM: y = -0.0076x - 0.5865
R² = 0.9984
-3
Linear (20 mM)
Linear (30 mM)
Linear (40 mM)
-3.5
Time (ns)
Figure 6: Plot of the natural log of emittance intensity (arb units) vs. time (ns). The kobs values
are represented by the negative slope of the linear best-fit equations. The R-squared values for
each concentration determine the quality of fit of the trend line.
The data included in the graph above was truncated in order to exclude all “noise”, or the
data not chemically relevant to the fluorescence of pyrene. Since the lifetime of *Py is known to
be between 100 and 300 ns, truncating the data on either end of this range will not affect the
results of the calculations for the rate constants.1 The initial noise and rise time as the pyrene is
excited from the photon and the final noise after the completion of the fluorescence of *Py were
eliminated to ensure that only the chemically-important data would be studied.
From the linear best-fit equations, the kobs value for each concentration of I- was
determined from the slopes of each line. The kobs values for each concentration are shown in the
table in Figure 7 below.
Pyrene Fluorescence Quenching by I- Anion
[I-] (mM)
0
10
20
30
40
Helfrich 7
k(obs) (1/s)
3.30E+06
5.00E+06
6.90E+06
8.90E+06
7.60E+06
Figure 7: Table of [I-] with the correlating kobs value. These numbers come from the best-fit
trend lines in Figure 6.
After determining the kobs values for each concentration, a graph of kobs vs. [I-] was
constructed which can be seen below in Figure 8. The linear best-fit line shows the relationship
between the quenching rate constant (kq) and the spontaneous fluorescence decay rate constant
(ko); the algebraic relationship can be expressed through the following equation: kobs=(kq)*[I-] +
ko, where kq is the slope and ko is the y-intercept. From the linear best-fit graph and the linear
regression (see Uncertainty Analysis section in the Appendix for the linear regressions), the
value of ko is 3.84*106 ± 8.79*105 s-1and kq to is 1.25*105 ± 3.59*104 mM-1 s-1.
Observed Rate of Decay vs. Quencher
Concentration [I-]
1.00E+07
y = 125000x + 4E+06
R² = 0.8016
k(obs) (1/s)
8.00E+06
6.00E+06
Series1
4.00E+06
Linear (Series1)
2.00E+06
0.00E+00
0
10
20
30
40
Quencher Concentration [I-] (mM)
50
Pyrene Fluorescence Quenching by I- Anion
Helfrich 8
Figure 8: Plot of kobs vs. concentration of KI. The y-intercept recpresents ko which is equivalent
to (3.8 ± 0.9)*106 s-1, the spontaneous fluorescence rate constant. The slope of the line
represents the kq value, or the rate constant for the [I-] quenching mechanism.
A linear regression was performed in Excel for each ln(emittance intensity) vs. time graph and
for the kobs vs. [I-] graph. The results from these regressions were incorporated into the standard
errors provided above. The linear regression analysis data can be found in the Appendix under
Uncertainty Analysis.
Discussion
From the data gathered above, several conclusions can be drawn. It should be noted that
the 30 mM KI solution data has a steeper decline, or faster quenching rate, than the 40 mM KI
solution data, opposite of what was expected .
The primary reason for the cause of this error has been determined to be errors in the
serial dilution. The precision of the instruments used (reference the Uncertainty Calculations of
[KI] in the Appendix) alone does not account for the error; however, compounded with the
effects of human error such as an extra drop on the outside of a pipette or inaccurate
measurements, this hypothesis can explain the deviation of the results from the literature values.
As depicted in the Experimental section, the lab group created 10 mL of stock solution of
0.1 M ± 7.41*10-4 M KI in 50% ethanol-water solution. A total of 6 ± 0.06 mL were removed
from the stock solution to create the 30 mM, 20 mM, and 10 mM solutions. The remaining
solution was diluted in 50% ethanol-water to form a 40 mM solution. During the serial dilution,
it is believed the lab group transferred more volume to each flask than required leaving a lack of
KI in the 40 mM flask. This lead to the rate constant for the 40 mM solution to be almost
equivalent to the 30 mM solution.
Pyrene Fluorescence Quenching by I- Anion
Helfrich 9
This plausible explanation is further endorsed by the following information. First, there
is no evidence of contamination of the KI samples. If contamination had occurred, there would
be noticeable deviations from the exponential decay equations of the graph is Figure 4.
Similarly, the graph in Figure 6 of the natural log of the emittance intensity versus time would
have noticeable deviations from the linear best-fit equations. The R-squared values of each bestfit line prove that the fit is very good, since the values are very close to one. It is expected that
the natural log of the y-values would show a linear relationship since the reaction is pseudo-first
order, meaning it is only dependent on the concentration of the quencher in this case.
Furthermore, there is little evidence to support the hypothesis that enough oxygen entered
the 40 mM KI solution sample to affect the rate of fluorescence decay by such a great amount.
Since the procedure for purging the oxygen from the sample was followed closely by all lab
members, the lab group was able to rule out this hypothesis. Also, it is very difficult to measure
the amount of oxygen in a sample; since this value is very likely to be negligible, the lab group
decided this conclusion was not worth investigating further.
In addition, the data from the 0 mM KI solution (the inherent sample) proves that the
equipment and apparatus used were functioning properly. The data and graphs from the 0 mM
KI solution were right on track with the literature expectations. This also points to an error in the
serial dilution as the 0 mM KI solution is the only sample that was not part of the serial dilution.
After reviewing all the above hypotheses, it is apparent that the error must have occurred
during the serial dilution phase of the experiment. The 10 mM, 20 mM, and 30 mM KI solutions
all appear to have a similar trend in the increase of the kobs value as the concentration increases.
This trend is most noticeably seen in the graph of kobs vs. [I-] in Figure 8 above. They form
almost a direct linear relationship. This would make sense if extra solution was transferred from
Pyrene Fluorescence Quenching by I- Anion
Helfrich 10
the 40 mM to the 10, 20, and 30 mM KI solutions; the amount transferred over the intended
amount is proportional to a constant for these three concentrations.
Slight deviations from literature values can also be accounted for by the precision limitations
of equipment used in the lab. During this experiment, uncertainties were calculated for each
measurement affected by the following equipment: Mettler AE100 balance, 10mL volumetric
flask (Class B), and 1mL glass pipette. The uncertainties of these pieces of equipment are listed
in the Appendix under Uncertainty Calculations.
A suggestion to increase the accuracy of the experiment is to start with a stock solution of
100 mL instead of 10 mL. During the serial dilution, 10 mL, 20 mL, and 30 mL would be
transferred to separate flasks to form 10, 20, and 30 mM KI solutions. The increase in volume
would ensure that deviations due to pipetting error would be more negligible.
Another aspect to consider for future experiments would be to compare kq values of different
quenching agents to evaluate the strength of different quenchers; the lab groups could then
identify what properties make one quencher superior to another.
A final suggestion would be to add a mechanism such as an analyzer or a separate
experiment to determine the amount of oxygen present in each sample. This data would prove
the negligible amount of oxygen in each sample and therefore disregard the hypothesis that the
oxygen interfered with the quenching rate constant in differing magnitudes for different
concentration samples.
Conclusion
Overall, the experiment was a limited success. The objectives of the lab, to determine the
rate constants ko and kq, were met and the theory behind the experiment was recognized;
however, with the possibility of using the wrong concentrations, the rate constants obtained
Pyrene Fluorescence Quenching by I- Anion
Helfrich 11
cannot be trusted without repeating the experiment. The kq and ko rate constants were
determined from the slope and y-intercept respectively of the kobs vs. [I-] plot. The kq value was
found to be (125± 35.9)*104 M-1 s-1 for I- as the quenching agent in 50% ethanol-water. The ko
value was calculated to be (3.8 ± 0.9)*106 s-1.
Although there was one major deviation from the expected results, the fact that the 30 mM
KI solution decayed at a faster rate than the 40 mM KI solution, the errors in serial dilution can
explain this result. Furthermore, the simple fix of increasing the volume of the initial 0.1 M KI
stock solution will quickly and effectively eliminate this error in future experiments.
In summation, I learned how to experimentally calculate rate constants from a graph of
collected data. I also learned that as the concentration of a strong quencher increases, the rate of
decay will increase. The material learned from both the successes and errors in the lab provided
for an effective learning experiment.
Appendix
Acknowledgments
I would like to acknowledge Jennifer Tan, Dr. Doug Archibald, and Dr. Bratoljub H.
Milosavljevic for their combined help both during and outside of the lab. Their help was
instrumental in our understanding of both the lab procedure and the final results.
Literature Cited
1. Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
“Time Resolved Pulsed Laser Photolysis Study of Pyrene Fluorescence Quenching by IAnion.” University Press: University Park, 2013.
2. “Electron Structure of Atoms.” Principles of Chemistry.
<http://faculty.colostatepueblo.edu/linda.wilkes/111/3c.htm>. Web. 7 September 2013.
Pyrene Fluorescence Quenching by I- Anion
Helfrich 12
3. Reusch, William. "Aromaticity." N.p., 9 May 2013. Web.
<https://www2.chemistry.msu.edu/faculty/reusch>8 Sept. 2013.
4. "Pyrene." Agency for Toxic Substances and Disease, n.d. Web.
<http://www.epa.gov/osw/hazard/>.7 Sept. 2013.
Sample Calculations
1. Calculate the amount of KI needed to create 10 mL of a 0.1M KI solution
0.1 mol KI
165.998 g KI
1L
mol KI
1000 mL
L
10 mL
= 0.165998 g KI
2. Calculate the concentration of KI solution in 10 mL volumetric flask:

10 mM KI solution
1 mL
0.1 mol KI
L
1L
1000 mL
1000 mmol
1 mol
= 0.1 mmol KI
CKI,10 = (0.1 mmol KI)/(0.01 L) = 10 mM

20 mM KI solution
2 mL
0.1 mol KI
L
1L
1000 mL
1000 mmol
1 mol
= 0.2 mmol KI
CKI,20 = (0.2 mmol KI)/(0.01 L) = 20 mM

30 mM KI solution
3 mL
0.1 mol KI
L
1L
1000 mL
1000 mmol
1 mol
= 0.3 mmol KI
CKI,30 = (0.3 mmol KI)/(0.01 L) = 30 mM

40 mM KI solution
4 mL
0.1 mol KI
L
1L
1000 mL
1000 mmol
1 mol
CKI,10 = (0.4 mmol KI)/(0.01 L) = 40 mM
Uncertainty Analysis
= 0.4 mmol KI
Pyrene Fluorescence Quenching by I- Anion
Helfrich 13
1. Linear Regression Analysis of plot LN(Emission Intensity) vs. Time (s): 0 mM
Regression Statistics
Multiple R
0.9994883
R Square
0.9989769
Adjusted R
Square
0.9989762
Standard Error
0.0176017
Observations
1457
ANOVA
df
Regression
1
Residual
1455
Total
1456
Intercept
Time (ns)
SS
440.16664
0.4507867
440.61743
MS
440.16664
0.0003098
F
1420721.6
Significance F
0
P-value
Lower 95%
Coefficients
Standard
Error
-0.4377351
0.0009351
-468.11111
0
-0.4395694
-0.003267
2.741E-06
-1191.9403
0
-0.0032724
t Stat
Upper
95%
0.4359008
0.0032616
Lower
95.0%
Upper
95.0%
-0.4395694
-0.4359008
-0.0032724
-0.0032616
2. Linear Regression Analysis of plot LN(Emission Intensity) vs. Time (s): 10 mM
Regression Statistics
Multiple R
0.9994549
R Square
0.9989102
Adjusted R
Square
0.9989092
Standard Error
0.0204429
Observations
1077
ANOVA
df
1
1075
1076
SS
411.781201
0.449255
412.230456
Intercept
Coefficients
-0.5181162
Standard
Error
0.00126934
t Stat
-408.1766
Time (ns)
-0.0049721
5.009E-06
-992.63831
Regression
Residual
Total
MS
411.7812
0.0004179
F
985330.81
P-value
Significance
F
0
0
Lower 95%
-0.5206069
Upper 95%
-0.5156255
Lower
95.0%
-0.5206069
Upper
95.0%
-0.5156255
0
-0.0049819
-0.0049623
-0.0049819
-0.0049623
3. Linear Regression Analysis of plot LN(Emission Intensity) vs. Time (s): 20 mM
Regression Statistics
Multiple R
0.9990117
R Square
0.9980243
Adjusted R Square
0.9980222
Standard Error
0.0327356
Observations
927
ANOVA
df
Regression
Residual
Total
1
925
926
Coefficients
SS
500.730597
0.99124944
501.721847
MS
500.7306
0.0010716
F
467264.63
Significance
F
0
Standard
t Stat
P-value
Lower 95%
Upper 95%
Lower
Upper
Pyrene Fluorescence Quenching by I- Anion
Intercept
Time (ns)
Helfrich 14
-0.610029
Error
0.0021975
-277.60134
0
-0.6143416
-0.6057163
95.0%
-0.6143416
95.0%
-0.6057163
-0.0068662
1.0045E-05
-683.56758
0
-0.0068859
-0.0068464
-0.0068859
-0.0068464
4. Linear Regression Analysis of plot LN(Emission Intensity) vs. Time (s): 30 mM
Regression Statistics
Multiple R
0.9992073
R Square
0.9984152
Adjusted R
Square
0.998413
Standard Error
0.0302012
Observations
739
ANOVA
df
1
737
738
SS
423.4956063
0.672227493
424.1678338
Intercept
Coefficients
-0.4482895
Standard
Error
0.002283097
t Stat
-196.3515
Time (ns)
-0.0088713
1.30193E-05
-681.39676
Regression
Residual
Total
MS
423.49561
0.0009121
F
464301.54
P-value
Significance
F
0
0
Lower 95%
-0.4527716
Upper 95%
-0.4438073
Lower
95.0%
-0.4527716
Upper
95.0%
-0.4438073
0
-0.0088969
-0.0088458
-0.0088969
-0.0088458
5. Linear Regression Analysis of plot LN(Emission Intensity) vs. Time (s): 40 mM
Regression Statistics
Multiple R
0.9992046
R Square
0.9984099
Adjusted R
Square
0.998408
Standard Error
0.030144
Observations
863
ANOVA
df
1
861
862
SS
491.2290502
0.782358122
492.0114083
Intercept
Coefficients
-0.5865165
Standard
Error
0.002096976
t Stat
-279.69637
Time (ns)
-0.0075711
1.02971E-05
-735.25976
Regression
Residual
Total
MS
491.22905
0.0009087
F
540606.92
P-value
Significance
F
0
0
Lower 95%
-0.5906323
Upper 95%
-0.5824008
Lower
95.0%
-0.5906323
Upper
95.0%
-0.5824008
0
-0.0075913
-0.0075509
-0.0075913
-0.0075509
Uncertainty Calculations of [KI]
Uncertainty of Mettler AE100 balance: +- 0.0004 g
Uncertainty of 10 mL volumetric flask (assume Class B): +-0.05 mL
Uncertainty of 1 mL glass pipette: +- 0.01 mL
Pyrene Fluorescence Quenching by I- Anion
Helfrich 15
1. Stock 0.1 M solution KI
0.1659 𝑔 𝐾𝐼 ∗
𝐶=
𝑚𝑜𝑙
= 0.001 𝑚𝑜𝑙 𝐾𝐼
165.9 𝑔 𝐾𝐼
𝑚𝑜𝑙
0.001 𝑚𝑜𝑙 𝐾𝐼
=
= 0.1 𝑀 𝐾𝐼
𝑣𝑜𝑙𝑢𝑚𝑒
0.01 𝐿
Relative Uncertainty: (flask) + (balance)
0.05 0.0004
+
= 0.007411
10
0.1659
Uncertainty:
C = 0.1 M ± 7.41*10-4 M
2. 30 mM solution KI
1𝐿
3 𝑚𝐿 ∗ 1000 𝑚𝐿 ∗ 0.1 𝑚𝑜𝑙/𝐿
𝑚𝑜𝑙
𝐶=
=
= 0.03 𝑀 𝐾𝐼
𝑣𝑜𝑙𝑢𝑚𝑒
0.01 𝐿
Relative Uncertainty: (3X pipette) + (flask) + (uncertainty of stock solution)
0.01 + 0.01 + 0.01 0.05 7.41 ∗ 10−4
+
+
= 0.02241
3
10
0.1
Uncertainty:
C = 0.03 M ± 6.72*10-4M
[I-] (mM)
Uncertainty
Concentration with
Uncertainty
10
2.24*10-4
0.01 M ± 2.24*10-4M
20
4.48*10-4
0.02 M ± 4.48*10-4M
30
6.72*10-4
0.03 M ± 6.72*10-4M
40
0.04 M ± 8.96*10-4M
Figure 9: Table of [KI] uncertainty values
8.96*10-4