CHM 1102 FSU Concentration of Stock Ferrate Solution Questions

SampleTrial1
Trial2
Absorbance at 510
nm
0.333
0.340
Diluted Conc. of Ferrate
(M)
0.0002895652
0.0002956522
Stock Concentration of Ferrate
(M)
0.0001447826
0.0001478261
Actual Yield of Ferrate concentration (average of two trials from stock) (M) ________________
Theoretical Yield of Ferrate concentration (calculated) (M) ______________________________
Percentage Yield ________________________________
Time
(sec)
1
1 st Reaction
Absorbance at
510 nm
Time
(sec)
2 nd Reaction
Absorbance at
510 nm
0
30
60
90
120
150
180
210
240
270
300
0.169
0.161
0.155
0.150
0.144
0.141
0.134
0.127
0.124
0.118
0.111
0
30
60
90
120
150
180
210
240
270
300
0.145
0.128
0.110
0.094
0.077
0.065
0.050
0.037
0.043
0.043
0.066
Initial Rate of Reaction 1 (include units):
Initial Rate of Reaction 2
Value of R2 :
(include units):
Results
Sample calculations included.
Results
Results will be briefly analyzed and explained.
Time (sec) Table
for additional
reaction if
needed
Value of R2
Reaction
Absorbance at
510 nm
Discussion
States the research question and purpose of the research.
What effect will changes in the concentration of DTZA have on the reaction between ferrate and
DTZA?
Hypothesis Statement:
As the concentration of DTZA increases, the reaction rate increases.
Procedure (in outline form):
Use provided 0.040 M DTZA solution to dilute the four test samples.
Prepare 2 mL of the 0.040 M DTZA solution by a graduated cylinder.
Use another graduated cylinder to measure 2mL, 4mL, 6mL, 8mL deionized water, respectively.
Use four test tubes to contain the four DI water in different volumes. Then, pour the 2 mL of the
0.040 M DTZA solution into each test tube. Slightly swirl the tube to fully mix.
No. 1 No. 2 No. 3 No. 4
DTZA volume (mL)
2
2
2
2
DI water volume (mL)
2
4
6
8
Diluted DTZA concentration (M) 0.020 0.013 0.010 0.008
Reaction rate
Use a graduated cylinder to measure the 1.5 mL diluted DTZA solution then add it into the
cuvette.
Take 1.5 mL of diluted FeO42- solution from part 2 into the cuvette and swirl gently the cuvette
for 5 seconds.
Place the cuvette in the spectrometer to measure the absorbance. Record the data from the
apparatus then input the data to the Spreadsheet to calculate the slope of the concentration of
ferrate vs. time. Then slope is going to be the reaction rate and record in Table 4.
Repeat the step 4-6 for the rest of three diluted DTZA solution. Plot diluted DTZA concentration
vs. reaction rate to see if the hypothesis statement is correct.
Discussion
Hypothesis is stated.
Discussion
Variables (independent, dependent, constant) are identified.
Discussion
Correlation of data and hypotheses are explained. Include references as needed.
FERRATE: AN ENVIRONMENTALLY FRIENDLY OXIDANT
BACKGROUND
The topic of this experiment was inspired by research done in Dr. Virender Sharma’s lab
in the Department of Chemistry. Dr. Sharma studied the redox reactions involving metal cations
with high oxidation numbers. He performed these reactions in aqueous solutions so that they’d
mimic the aquatic environment. Dr. Sharma used his knowledge of these chemical reactions to
discover ways to remove pollutants from natural waters and drinking water sources.1
Illustration reprinted from AquaOx of Texas
Pharmaceutical drug companies have made great advances in treating many diseases and
illnesses. Unfortunately, the active chemicals in pharmaceuticals often find their way into
drinking water across the country.2 The concentration of these chemical compounds range from
ng/L to μg/L concentrations3,4 and although these amounts seem small, the chemicals can be very
potent. For example, endocrine disruptors, a type of chemical used in human hormone
supplements, can adversely affect hormone levels in reptiles. In general, the increasing presence
of pharmaceuticals and personal care products in natural and drinking water sources is a concern
to environmental scientists and the general public.
Chemists, biologists, and engineers are studying ways to remove trace amounts of these
chemicals from water. One possible method is to use chemicals known as ferrates to oxidize the
polluting chemicals. Ferrate is an ion, FeO42-, containing an iron atom in its +6 oxidation state.
This ionic iron oxide is commonly referred to as Fe(VI). Iron is much more stable as a metal
(zero oxidation state), or as an ion in its +2 or +3 oxidation state. Therefore, ferrate easily
participates in reactions that allow it to gain electrons (reduction) to change its +6 oxidation state
to +3 and concurrently oxidize other chemicals. It can oxidize most pharmaceuticals in water.
Iron(III) cations are commonly found in nature so the formation of Fe3+ from ferrate has no
noticeable effect on the environment.5 Ferrate has the potential to be an environmentally friendly
chemical that can effectively remove many different pollutants from water.
Ferrate can be synthesized using an electrochemical reaction, a dry chemical oxidation
(no water), or wet chemical oxidation.6-8 In this experiment, you will prepare sodium ferrate
(Na2FeO4) using a wet chemical method. Sodium ferrate forms a purple colored solution when
added to water. In solution, ferrate will slowly react with water but it remains effective for a
couple of weeks if kept dry.
As ferrate oxidizes a pharmaceutical compound, the purple color of FeO42- disappears
and is replaced by the yellow-brownish color of Fe3+ (in the form of iron hydroxides and iron
oxide). This change in color can be monitored using a spectrometer that records the absorbance
of light within the visible spectrum. The purple color of ferrate solutions is due to its absorbance
of light with a maximum absorbance at 510 nm.9
One important aspect of ferrate’s reaction with a pharmaceutical is how fast it reacts (the
reaction rate). The rate of the reaction can be determined by measuring the change in ferrate
concentration during the beginning of the reaction. As you’ve learned in previous experiments,
Beers’ Law shows that the concentration of ferrate is related to the solution’s absorbance at 510
nm. You will use a spectrometer to measure the absorbance of ferrate and then use that
information to study the reaction rate. Measuring reaction rates is part of a larger field of
chemistry known as kinetics.
Diatrizoic acid, DTZA (Figure 1) is an x-ray image contrast media (ICM) compound
mainly used to help in imaging soft tissues in the medical industry.10 Due to the large quantity
used daily, DTZA is found in waste water and hospital effluents.11 Fe(VI) has been used to
demonstrate its ability to remove DTZA from water.12 The kinetics experiments of Fe(VI) and
DTZA will therefore be studied here.
HO
O
C
I
CH3
C
C
O
C
I
C
C
CH3
C
C
N
C
N
H
I
H
Figure 1. Diatrizoic acid, DTZA
O
Background References
1. Florida Institute of Technology, Faculty Profiles.
https://services.fit.edu/profiles/profile.php?value=83
2. Schultz, M. M.; Furlong, E. T.; Kolpin, D. W.; Werner, S. L.; Schoenfuss, H. L.; Barber, L.
B.; Blazer, V. S.; Norris, D. O.; Vadaz, A. M. Antidepressant Pharmaceuticals in Two U.S.
Effluent-Impacted Streams: Occurrence and Fate in Water and Sediment, and Selective
Uptake in Fish Neural Tissue. Environ. Sci. Technol. 2010, 44, 1918-1925.
3. Kolpin, D. W.; Furlong, E. T.; Meyer, M. T.; Thurman, E. M.; Zaugg, S. D.; Barber, L. B.;
Buxton, H. T. Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in
U.S. Streams, 1999-2000: A National Reconnaissance. Environ. Sci. Technol. 2002, 36,
1202-1211.
4. Ternes, T. A.; Joss, A.; Siegrist, H. Scrutinizing pharmaceuticals and personal care products
in wastewater treatment. Environ. Sci. Technol. 2004, 38, 392A-399A.
5. Sharma V. K. Potassium ferrate(VI): An environmentally friendly oxidant. Adv. Environ.
Res. 2002, 6, 143-156.
6. Ibanez, J. G.; Tellez-Giron, M.; Alvarez, D.; Garcia-Pintor, E. J. Laboratory experiments on
the electrochemical remediation of the environment. Part 6: Microscale production of ferrate.
J. of Chem. Ed. 2004, 81, 251-254
7. Bouzek, K.; Rousar, I. The study of electrochemical preparation of ferrate(VI) using
alternating current superimposed on the direct current. Frequency dependence of current
yields. Electrochim. Acta 1993, 38, 1717-1720.
8. Thompson, G. W.; Ockerman, L. T.; Schreyer, J. M. Preparation and purification of
potassium ferrate(VI). J Amer. Chem. Soc. 1951, 73, 1379-1381.
9. Sharma, V. K.; Mishra, S. K.; Ray, A. K. Kinetic assessment of the potassium ferrate(VI)
oxidation of antibacterial drug sulfamethoxazole. Chemosphere 2006, 62, 128-134.
10. Steger-Hartmann, T.; Lange, R.; Schweinfurth, H. Environmental Risk Assessment for the
Widely Used Iodinated X-Ray Contrast Agent Iopromide (Ultravist). Ecotoxicol. Environ.
Saf. 1999, 42, 274-281.
11. Kalsch, W. Biodegradation of the iodinated X-ray contrast media diatrizoate and iopromide.
Sci. Total Environ. 1999, 225, 143-153.
12. Anquandah, G.; Ray, M. B.; Ray, A. K.; Al-Abduly, A. J.; Sharma, V. K. Oxidation of X-ray
compound Diatrizoic acid by Ferrate(VI). Environ. Technol. 2010 ( in press)
SKILL-BUILDING EXERCISES
This week’s experiment begins with four activities. First, you will synthesize sodium ferrate
using a wet chemical method. You will then calculate the yield of sodium ferrate that you
produced. Next, you will use Beer’s Law to convert absorbance readings to actual concentration
values of ferrate. Last, you will perform a redox reaction involving sodium ferrate and a
pharmaceutical pollutant and measure the rate of that reaction using information in the Excel
spreadsheet.
Part 1. Synthesizing Sodium Ferrate
Solutions of FeCl3 are provided. Sodium ferrate forms through the following reaction:
2 FeCl3(aq) + 3 NaClO(aq) + 10 NaOH(s) → 2 Na2FeO4(aq) + 9 NaCl(aq) + 5 H2O(l)
NaClO is an active component of bleach. Very concentrated solutions of bleach are used as
“liquid chlorine” for swimming pools.
NOTE: Perform this synthesis in the fume hood. The solution will be very basic so always
wear goggles and gloves when performing this synthesis. If you get any solution on your hands,
wash them immediately with soap and water and notify your GSA.
1. Measure 20 mL of commercial bleach in a graduated cylinder and pour into a 150mL beaker.
Add a stirring bar to the beaker and place on a stir plate.
2. Add 10 g of NaOH pellets to the beaker of bleach and begin stirring. This is an exothermic
reaction so the beaker will get warm. Make sure your sample fully dissolves before
continuing.
3. Pipette 1 mL of 0.15 M FeCl3 using the plastic pipette into the dissolved NaOH solution
while it is still warm.
4. Allow the mixture to stir for approximately 10 minutes. Let the solution cool for another 3-5
minutes. The formation of the Na2FeO4 will cause the solution to appear a dark purple.
5. Assemble a suction filtration apparatus to the water faucet as shown below (check with your
GSA).
6. Using a sintered glass filter on top of the vacuum filtration flask, turn on the vacuum and
slowly add the sodium ferrate solution. This will filter the sodium ferrate solution. The
liquid which passes through the filter (called the filtrate) is a concentrated solution of
sodium ferrate.
Important: Make sure you obtain a clean sintered glass filter. A clean sintered glass filter
makes the filtration faster. When the reaction is complete, immediately notify the GSA to
remove the sintered glass filter for you and place it in the muriatic acid cleaning solution in
the fume hood.
7. Using a funnel, pour your solution into a graduated cylinder to measure the volume of ferrate
solution that you prepared.
8. Store the sodium ferrate solution in a plastic bottle. Label the bottle with the following
information:
a. Name of Team Manager
b. Write “sodium ferrate in water”
c. Concentration of sodium ferrate (will be determined later)
d. Date
e. Lab section number
Part 2. Calculate the Percent Yield of Ferrate Produced
In the reaction that you just performed, FeCl3 is the limiting reagent. After calculating the
theoretical yield (for review, see pages145-151 in your textbook, Tro 3rd edition) of sodium
ferrate in moles, determine its theoretical concentration in molarity (M) using the initial total
volume of the solution. You will calculate the actual concentration of sodium ferrate (diluted
concentration of ferrate) in your solution using absorbance and Beer’s Law.
1. Calibrate the SpectraVis spectrometer using a cuvette of DI water. The SpectraVis should be
in full spectrum mode when calibrating.
2. Remove all the DI water from the cuvette.
3. Add 5 mL of your ferrate solution to 5 mL of DI water. Add this sodium ferrate solution to
the cuvette (slightly more than half full). Keep the remaining solution; you will use it
again in part 3, collect in clean beaker.
4. Record the absorbance of your sodium ferrate solution at 510 nm. If the absorbance is 1.5 or
greater, then dilute your solution again. Take the dilution factor into account when
performing calculations.
5. Pour the ferrate solution in a clean beaker (so that it can be used in DTZA oxidation
experiment). Rinse out the cuvette with DI water three times and discard it into your waste
beaker. Tap the cuvette against a paper towel to remove as much water droplets as you can.
6. Repeat steps 3-5 to record another absorbance value.
7. Calculate the diluted concentration of ferrate using Beer’s Law: the pathlength of the cuvette
is 1.0 cm, the molar absorptivity, , is 1150 M-1 cm-1 and the absorbance obtained. The
dilution will be considered when calculating the concentration of the stock solution.
8. Record the concentration of the stock values for both trials on the data sheet and find the
average concentration to figure your actual yield. Calculate the percent yield using the
theoretical and actual yield for your reaction. Record the concentration on your container of
sodium ferrate for easy future reference.
Part 3. Performing the Reaction between Ferrate and Diatrizoic Acid (DTZA)
You will perform the reaction of ferrate and DTZA to determine how fast the reaction proceeds.
The rate calculations for this reaction are embedded in the Excel spreadsheet using the data that
you collect in the lab. The absolute value from the slope of the best-fit line equation will
represent the rate of the reaction.
You will perform the ferrate-DTZA reaction two times. Results of the two FeO42–DTZA
reactions should be very similar but they won’t be exactly the same due to experimental error
(including human error and uncertainties that are inherent in the experimental process).
Steps 1 – 3 describe how to prepare for the reaction. Steps 4 – 8 explain how to perform the
FeO42–DTZA reaction that you will complete two times.
1. Calibrate the SpectraVis with DI water in full spectrum mode and then discard the water.
Set the spectrometer to time-based mode and measure the absorbance at 510 nm.
a. Click “full spectrum” in the top right corner of the spectrometer. Scroll through
the menu and click “time-based.”
b. Set the time to 300 seconds (5 mins). Make sure the spectrometer is at a rate of
0.5 sample/s and an interval of 2 s/sample. Press OK.
c. When the LabQuest returns to the home screen, click on the red box, then go to
“change wavelength.” Set the wavelength to 510 nm. Record the exact
wavelength measured by the LabQuest if it’s different than 510 nm.
2. Make sure that your cuvette is clean and dry before proceeding.
3. Pipette 1.5 mL of the 0.040 M DTZA solution into the cuvette.
Important: Label your pipettes, one for DTZA and the other for sodium ferrate. Do not
mix up your pipettes.
4. Perform the following steps together quickly and in the following order:
a. Add 1.5 mL of your diluted FeO42- solution (from part 2) to the DTZA solution in the
cuvette.
b. Shake the capped cuvette vigorously for 5 seconds.
c. Place the cuvette in the spectrometer and measure the absorbance. Note the time of this
measurement.
d. Record the time and absorbance value on your data sheet.
5. Record the measured absorbance values on your data sheet approximately every 30 seconds
for 5 minutes. Record the exact times that you measure the absorbance.
6. Discard the ferrate-DTZA solution in the waste beaker. Rinse out the cuvette three times
with DI water and discard these contents into the waste beaker as well.
7. Repeat steps 4 – 6 again.
8. Clean up your work area and turn in your completed data sheets. Dispose the contents of
your waste beaker in waste container B. Make sure you give your ferrate solution to the
GSA so it can be stored until you need it next week.
Record the absorbance values into the Excel spreadsheet. Follow additional instructions found in
the Excel spreadsheet in order to analyze the data.
POSSIBLE RESEARCH OPTIONS FOR LAB EXPERIMENT WEEKS 2 AND 3
Based on the preliminary work you did in the skill-building portion of this experiment,
there are several areas for investigation. You will choose one of these areas before you leave lab
on the day of the skill-building exercise and report it to your GSA. Between week 1 and 2 of the
experiment, you will meet with your team members to write a hypothesis statement for the
research question your team chose and to develop a method for testing that hypothesis. This
includes determining appropriate variables (independent, dependent, and control). As a
reminder, a hypothesis is a testable generalization which states the relationship between two
selected variables under specified conditions. An independent variable is what is changed in
order to do your experiment. A dependent variable depends on the outcome of the independent
variable. For example, if you were determining the growth rate of a plant when exposed to
different amounts of light, the light duration would be the independent variable, whereas the
growth rate itself is the dependent variable. Control variables are variables put in to control the
system.
For example, in the plant growth rate experiment, a control variable might be the
addition of a set amount of water supplied to all plants during the experimentation process.
Here are several research options for this particular experiment:
1) What effect will changes in the concentration of ferrate have on the reaction between ferrate
and DTZA? To review dilution calculations, see pages 142-144 in your textbook.
2) What effect will changes in the concentration of DTZA have on the reaction between ferrate
and DTZA? To review dilution calculations, see pages 142-144 in your textbook.
3) What effect will temperature have on the reaction between ferrate and DTZA? The
temperature of the ferrate and DTZA solutions should be the same. Ice baths and hot plates
are available. Both DTZA and ferrate solutions should be at the desired temperature before
the reaction begins. Prior to measuring the absorbance, shake the cuvette briefly to keep the
solution mixed then immerse the cuvette in the warm or cold water so that the solution’s
temperature remains constant. Dry any water droplets from the outside of the cuvette before
recording an absorbance measurement.
Data Sheet Ferrate
Names
Part 2. Calculate the Percent Yield of Ferrate Produced
Sample
Absorbance at 510 nm
Diluted Conc. of
Ferrate (M)
Stock Concentration
of Ferrate (M)
Trial 1
Trial 2
Actual Yield of Ferrate concentration (average of two trials from stock) (M) ________________
Theoretical Yield of Ferrate concentration (calculated) (M) ______________________________
Percentage Yield ________________________________
Part 3. Performing the Reaction between Ferrate and Diatrizoic Acid (DTZA) (WEEK 1)
Time (sec)
1st Reaction
Time (sec)
2nd Reaction
Time (sec)
Reaction
Table for
Absorbance at
Absorbance at
Absorbance
additional
510 nm
510 nm
at 510 nm
reaction if
needed
Initial Rate of Reaction 1 (include units):
Value of R2:
Initial Rate of Reaction 2 (include units):
Value of R2:
Performing the Reaction between Ferrate and Diatrizoic Acid (DTZA) (WEEK 2)
Time (sec)
1st Reaction
Absorbance at
510 nm
Time (sec)
2nd Reaction
Absorbance at
510 nm
Time (sec)
Table for
additional
reaction if
needed
Initial Rate of Reaction 1 (include units):
Value of R2:
Initial Rate of Reaction 2 (include units):
Value of R2:
Reaction
Absorbance
at 510 nm
CALCULATIONS
Show all calculations for dilute and stock concentration of ferrate, the theoretical yield, actual
yield, and percent yield on this page. For full credit, you must show a neat, logical setup and
include correct units as required.
Team Role Assignments and Research Option Choice for Experiment 6
Manager
____________________________________________________________
Chemist
____________________________________________________________
Instrument
Technician ____________________________________________________________
Software
Technician ____________________________________________________________
In one or two sentences, state your research option that you will investigate during the next two
weeks and your hypothesis statement. Be as specific as possible. Your GSA may ask you revise
your option if other teams have already chosen the same option.
Hypothesis Statement: ___________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Method or Plan of Investigation for Experiment 6
(Make a copy to turn in to GSA at the beginning of 2nd week of experiment.)
Names _____________________________________________
Hypothesis Statement:
Procedure (in outline form):
Section # _________
Topics for your results section:
Present your results in organized tables, figures, and/or graphs so that they are easy for your
GSA to understand. Prepare graphs using a spreadsheet program like Excel or Open Office.
Label your graph axes and write a title for each graph, figure or table. Do not prepare your
graphs by hand on graph paper.
If you use an equation for calculating your results, define the variables in the equation and use
correct significant figures.
Write about your results in sentences and paragraphs. Explain what is important about your
graphs, tables and/or figures of data. You do not need to explain every single result. Summarize
your results so that your GSA can understand the work that you did.
Topics for your discussion section:
Write a clear, scientific statement about the purpose of your research and the research question
your team is investigating.
Write a hypothesis statement. Your hypothesis should be a testable generalization which states
the relationship between two selected variables under specified conditions. It is OK if your
hypothesis statement turns out to be wrong – that is a part of research.
Define your independent, dependent, and control variables.
In three or four sentences, briefly explain how you modified the experiment handout procedure
in order to complete your research.
Explain how your results support or do not support your hypothesis.
Topics for your reflection section:
Explain your individual contribution to your lab group’s effort during the lab session and explain
how effectively you and your lab partner(s) worked together throughout the experiment.
Discuss any limitations of your experiment or mistakes you made and how they affect the final
results. Be specific – do not simply blame everything on “Human Error.”
Recommend reasonable suggestions for improving the experiment. Think about what you would
do differently if you could repeat your experiment.
CHM 1102 Study Guide for Exam 3
You will be given all equations, physical constants and a periodic table.
Chapter 14
1. Calculate overall rate of a reaction.
2. Write rate law expressions and calculate reaction orders using the method of initial rates.
3. Determine the units for rate constant, k, which depend on overall reaction order.
4. Calculate concentrations or rate constants using zero, lst- and 2nd-order integrated rate laws
and half-life equations.
5. Determine whether a reaction is zero, 1st- or 2nd-order from graphs of some function of
concentration vs. time. Know what the slopes and y-intercepts for each graph represent.
6. Know the effects of temperature and a catalyst on a reaction rate.
7. Define and calculate activation energy (Ea) and the pre-exponential factor (A) from the
Arrhenius equation. Be familiar with the relationship between rate constant, k, and activation
energy, Ea, using the Arrhenius equation.
8. Interpret an energy-reaction diagram and indicate the activation energy for the reaction.
9. Determine the rate law of an overall process from elementary reactions of its mechanism.
Determine the rate-determining step (RDS) based on relative speed of the elementary steps.
Identify intermediates and catalysts.
Chapter 18
1. Know the three Laws of Thermodynamics.
2. Predict the change in entropy of a system based on properties of reactants and products.
3. Understand how temperature affects the free energy of a reaction.
4. Calculate entropy and free energy changes for a reaction. This can be done using several
equations for G and S.
5. Convert between Keq and G values.
6. Determine a nonstandard free energy change.
Chapter 19
1. Identify the oxidation numbers of all atoms, the oxidizing and reducing agents and the
oxidation and reduction half reactions in a redox reaction.
2. Given a diagram of an electrochemical cell, identify and describe the components (anode,
cathode, salt bridge, wire and electrodes).
3. Use the table of standard reduction potentials to identify which half reactions can be
combined to form a spontaneous reaction.
4. Balance redox reactions in acidic and basic solutions.
5. Calculate standard and nonstandard cell potentials.
6. Convert between an electrochemical potential and a free energy change.
7. Perform calculations related to electrolysis, such as determining the time required to
electrolyze a given amount of reactant.
8. Describe the difference between a voltaic and electrolytic cell.