write a proposal on the photoreduction of iron(iii) to iron(ii) use the followin
ID: 1030516 • Letter: W
Question
write a proposal on the photoreduction of iron(iii) to iron(ii)
use the following information to help you:
Details to address in your plan
1. Beer-Lambert experiment plan
a. What is the possible range of iron(II) concentrations in your photoreduction experiments?
b. What range of iron(II) concentrations will you use in your standards for your Beer-Lambert experiment?
c. How will you prepare these solutions using the available chemicals and equipment?
d. How will you independently confirm the accuracy of your Beer-Lambert experiment results?
2. Repeating the photoreduction of iron(III) in the presence of tartaric acid
a. What are the details of your planned experiment?
b. How will you prepare the solutions you need using the available chemicals and equipment?
c. How will you analyze the results?
3. Modified photoreduction experiment
a. What is the question you are attempting to answer with this modified experiment? You need to be specific here. A vague question such as “Will the results be different if we do X?” will get no credit and will be sent back to you to do over!
b. How will you prepare the solutions you need using the available chemicals and equipment?
c. How will you analyze the results?
Equipment Available for Use
• student tray equipment
• volumetric flasks (either 500-mL or 1000-mL sizes)
• 1-cm cuvettes (used with the spectrometer)
• 100 x 50 mm crystallizing dishes (used to run your photoreduction experiments in the UV reactor; holds 100 mL of solution when about ½ full; do not fill over ½ full to prevent spills)
• Lab balances (these weigh to 1 milligram)
• Spectronic 20 Genesys Spectrometer (operating instructions are found in the document “A Pictorial Guide to the Laboratory” found on BlackBoard in the Student Resources folder under Course Content.)
• Orion Model 410A pH meter and combination electrode (operating instructions also on BB)
• Eppendorf M4 Repeater pipette (for precise dispensing of the ferrozine reagent, operating instructions also in the Student Resources folder on BB)
• UV Photoreactor – This is a goggle-sanitizer cabinet with a 0-15 minute timer for setting lamp run times. The cabinet has a safety interlock so the UV lamps will not operate with open doors. Reactor use protocol: As this is a shared resource for the whole section to use the following protocol will be used so teams can plan for their reaction runs.
o The reactor will be opened for adding and removal of samples at ~15 minute intervals.
o All teams have equal priority to have one sample in the reactor before any team puts in a second sample.
o All samples in the reactor must be labeled with the team name!
o Each team is responsible for monitoring the time and being prompt to remove their completed sample.
o Teams that are not ready to add a sample to the reactor will wait 15 minutes until the next opening to add their sample.
o Ordinary glassware absorbs almost all UV light and quartz labware, which is transparent to UV light, is very expensive and will not be available. All photoreduction runs will be made using an uncovered glass crystallizing dish to hold the solution. The reactor geometry has the UV lamps at the top of the cabinet so the light will be above the crystalizing dish. No team’s setup can block the light to other samples.
Reagents Available for Use
• iron(II) ammonium sulfate hexahydrate (solid)
• iron(III) nitrate nonahydrate (solid)
• tartaric acid (solid)
• salicylic acid (solid)
• glucaric acid (available as the potassium salt of saccharic acid) (solid)
• citric acid (anhydrous) (solid)
• 0.01M ferrozine solution (neutral pH solution in water)
• 1M NaOH
• 1M HCl
• standard pH calibration buffers (pH 4, 7, 10) General Lab Equipment and Supplies Available for Use
• aluminum foil
• digital thermometers
• digital timers
• DI water
• ice
• Kimwipes
• lab aprons
• lab gloves
• lab markers
• label tape
• magnetic stirrers/hotplates
• Parafilm
• plastic droppers
• scissors
Explanation / Answer
Background of the proposal
Fe 2+ is a principal micronutrient which has a few bioavailability in aquatic surfaces.
Fe(III) will encounter photoreduction with carboxylic acids when irradiated to obtain Fe 2+.
Tartaric acid can be apart of these reactions and act in photo reduction with ferrozine.
Methods
1. Create Beer-Lambert absorption plot.
2. Prepare stock solution 0.796g Fe with 500ml of water.
3. Dilute stock solution - mix 1 ml w/99 ml makes 10-15 M.
4. Create Fe2+ and Ferrozne solution.
5. Measure absorbance.
Step 1
Fe(III) :- 0.0202g in 500ml of water to make 0.02M Fe(III) solution.
Take 1.0ml of this solution and mix 99ml water to make 0.02M Fe(III) solution.
Tartaric acid:- 0.03g in 100ml of water to make 20mM solution.
Step2
Mix 60ml of each solution.
Step3
Place in UV chamber.
Step4
Measure absorbance.
Step 5
Compare values.
Take 10ml samples every 15 minutes. Add ferrozine to the sample. Measure absorbance at 562 nm three times with each sample.
Tabulate the values of concentration (mm) and absorbance reading.
Plot Beer-Lambert determination of Fe(III) graph by taking absorbance versus concentration. Draw best fitting straight line through the points.
Conclusions
Tartaric acid participated in the photoreduction of Fe(III).
Concentration of Fe in greater when it was mixed with tartaric acid.
Salicylic acid, Glicaric acid and citric acid can be tested by same procedure.
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