I need help with 6-10. I added first page of what I did.
6ãThe Dietary Supplement solution used in the experiment was diluted from the original concentrated supplement as purchased. Calculate the average concentration of iron(II) in the original supplement (in μgmL of liquid), using your average answer to QS and the dilution factor found on the on the label of the Dietary Supplement dispensing bottle. The reciprocal of the dilution fraction is called the dilution factor. For example, if the dilution is 1:250, the dilution fraction equals 1/250. Multiply the average iron(II) concentration in the diluted sample by the dilution factor (250/1 in this example) to find the average concentration of iron(II) in the original Dietary Supplement as purchased (concentrated). 7. Calculate the number of mL in a 4.0 fluid ounce bottle of liquid (such as a Dietary Supplement) given the conversion that there are 29.6 mL in one (1) fluid ounce. Show your answer in scientific notation to the correct number of significant figures. Based on your answer to Q7 and using the answer to Q6 as a conversion factor, calculate the total amount of iron(II) in micrograms (ug) from a 4.0 fluid ounce bottle of Dietary Supplement as purchased (concentrated). Show your answer in scientific notation to the correct number of significant figures. 8. vert micrograms 4.0 flui answer in scientific notation to the correct number of significant figures. from Q8 to milligrams to get the total amount of iron(I) from a d ounce bottle of Dietary Supplement as purchased (concentrated). Show your 9. Con 10. Deseribe the relationship between the concentration of iron(I) and sample color.
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Related questions
Using this information: I used 4.00 g potassium dichromate. The amount of Iron ll is 4.00 gram in 2nd flask. Used grey moose vodka 2.00 ml and filled flask with water. This was the 2% vodka solution. For the experiment I used 5.00ml of the vodka and added 35.00 ml of more water to make it 1/8 of 2% or 0.25% of the original. With this information and the answer's i have placed in the table please help with remainder of questions. Need to work to understand answers so I will get correct on upcoming test. Thanks.
Calculate the concentration of the dichromate ion in the first volumetric flask.
Calculate the concentration of the iron (II) ion in the second volumetric flask.
Experiment 2: Titrate the Vodka Sample
Lab Results
Record the following lab data in the table below. If you had to repeat one of the titrations, disregard the value that was different.
(a) volume of potassium dichromate solution added to the Erlenmeyer flask in mL | 5.00ml |
(b) coarse titration volume of iron (II) solution range in mL | 14.10 -14.15 ml |
(c) volume of iron (II) solution delivered from the burette in mL during the first fine titration | 14.13ml |
(d) volume of iron (II) solution delivered from the burette in mL during the second fine titration | 14.11ml |
(e) average volume of iron (II) solution used in the fine titrations | 14.12ml |
(f) the color of the analyte solution at the end point of the titration | purple |
(g) the color of the analyte solution after adding the indicator | dark green |
Data Analysis
Record and calculate the quantities in the table below using the data from your dichromate titrations. Use an average value for the volume of iron (II) solution used in the titration. If one of your values is very different, and you had to perform the titration three times, disregard the value that was very different when computing the average.
(a) volume of potassium dichromate solution added to the Erlenmeyer flask in mL 5.00ml | |
(b) moles of dichromate ion added to the Erlenmeyer flask | |
(c) average volume of iron (II) solution delivered from the burette in mL 14.12ml | |
(d) moles of iron (II) ions delivered from the burette | |
(e) moles of excess dichromate ions that reacted with the iron (II) ions (remember that the ratio in which they react is 1 dichromate : 6 iron (II)) | |
(f) moles of dichromate that reacted with the ethanol in the vodka (Subtract excess dichromate ions that reacted with the iron (II) ions from the original moles of dichromate ion present.) | |
(g) moles of ethanol in the 5 mL diluted vodka sample according to the stoichiometric ratio of 2 dichromate ions to 3 ethanol molecules |
The amount of alcohol in a drink is typically reported as percent alcohol by volume. Volume percent or volume/volume percent (% v/v) most often is used when preparing solutions of liquids. Volume percent is defined as:
% v/v = Vsolute/Vsolution à 100
Find the percent alcohol (ethanol) by volume for the vodka used in the lab by following the steps outlined in the table below.
(a) given the molar mass of ethanol of 46.07 g/mol, calculate the mass of alcohol (ethanol) in the tested sample solution | |
(b) given the density of ethanol of 0.7893g/ml, find the volume in mL of ethanol present in the diluted vodka solution | |
(c) record the volume of vodka used in the experiment in mL | |
(d) find the percent alcohol by volume (% v/v) in the diluted vodka solution | |
(e) the diluted vodka solution was prepared by diluting 2.00 mL vodka to 100.00 mL. Calculate the dilution factor used (N:1) | |
(f) multiply the percent alcohol by volume in the diluted vodka solution by the dilution factor to obtain the % v/v alcohol in the original vodka solution |
Conclusions
The Grey Moose vodka tested in this lab reports a percent alcohol by volume of 40.0% on its label. How does your value compare to the reported one? If the values are different, give one possible experimental error that might have contributed to the difference.
Potassium permanganate is another strong oxidizing substance similar to potassium dichromate. An acidic solution of purple permanganate ions can get reduced to colorless Mn2+ ions in the presence of ethanol. Write down the redox reaction between permanganate and ethanol, and balance it using the half-reaction method.
Besides vodka, there are other colorless alcohol-containing beverages that can be titrated following the procedure in your lab. Given the average values for the percent alcohol by volume listed in the table below, which beverage do you expect to use the least amount of iron (II) standard solution during the titration? Assume all lab procedures stay the same.
% alcohol by volume | |
White rum | 37.0% |
Vermouth | 18.0% |
White whine | 12.0% |
THIS IS A LAB REPORT THAT I NEED HELP WITH I NEED HELP WITH ANSWERING THE POST LAB QUESITON THAT IS ALL THE WAY IN THE BOTTOM PLEASE HELP ME ANSWER THE POST LAB QUESTIONS THANK YOU! THE PRE LAB I HAVE ALREADY DONE BTW!
Determination of Cobalt (II) Chloride
by UV/VIS Spectroscopy
Introduction
The absorption of specific quantities of electromagnetic (light) radiation by an element or compound allows electrons to move from lower energy level to a higher energy level. We say that the energy levels are quantized. Electrons, returning to lower energy levels, will release energy within the electromagnetic spectrum. The wavelengths may be in the ultraviolet, visible, or infra red regions of the spectrum. For cobalt (II) chloride, the compound of study, the visible region, of the spectrum will be addressed.
By knowing the wavelength (l) or frequency (n) of radiation, one may determine the energy of the transition. Relationship between energy, wavelength and frequency are:
c= ln and E= hn or E= hc/l
The light radiation absorbed in a solution of this salt is proportional to its concentration through a relationship provided by the Beer-Lambert Law:
A = kC
where A= absorbance, k is Beerâs Law constant, and C is the molar concentration in solution.
The absorbance (A), a unit-less number is dependant on the quantity of light energy absorbed and transmitted by the solution through the following equation:
A= -log T or A = 2-log %T
where T= transmittance= I/I0 where I is the absorbed light and I0 is the impinging light source.
Purpose
The purpose of this laboratory experiment is to practice, learn and carefully prepare molar solutions to investigate the relationship of concentration and spectrophotometer response. A 0.150 M solution of cobalt (II) chloride will be provided. You will prepare diluted solutions through the serial dilution method, measure the transmittance and calculate the absorbance values. You will prepare a Beerâs law graph of data; molar concentration vs. absorbance. Then determine Beerâs law constant using Microsoft Excel program.
You will also be given a concentrated sample of cobalt (II) chloride of unknown concentration and you must determine the appropriate dilution to prepare and thereafter determine the unknown concentration.
Procedure
In order to carry out this analysis procedure, it will be necessary to determine the wavelength of transition. Recall, that one specific energy maximum exists for each transition. We will study the transition in the range of 400- 600 nanometers (nm). This is the visible region of the spectrum.
Step 1. Prepare the following solution concentrations using the 0.150 M cobalt (II) chloride stock solution, 18 mm x 150 mm test tubes and Mohr pipets.
TABLE 1
Solution No. | 0.150 M CoCl2 (mL) | Volume water (mL) |
1 | 5.0 | 0.0 |
2 | 4.0 | 1.0 |
3 | 3.5 | 1.5 |
4 | 3.0 | 2.0 |
5 | 2.5 | 2.5 |
6 | 2.0 | 3.0 |
7 | 1.0 | 4.0 |
Step 2. Carefully place a cork or rubber stopper over each solution and mix the contents.
Step 3. Measure the transmittance of a 0.150M solution between 400 nm and 600 nm at 25 nm intervals.
To accomplish this, follow these steps:
Caution: instruments are delicate. If you are uncertain about instrument operation, ask your instructor for assistance. (Instructions on instrument operation- see next page.)
|
Instrument operation- edited version of product *Operatorâs Manual
Transmittance and Absorbance
1. Turn on the instrument by turning the Power Switch (10) clockwise. Allow the spectro-photometer to warm up for at least 15 minutes to stabilize.
2. After the warm-up period, set the desired wavelength with the Wavelength Control Knob.
3. Set the filter lever to the appropriate position for the selected wavelength (not required for SPECTRONIC® 20D).
4. Adjust the display to 0%T with the Zero Control (10). Make sure that the sample compartment is empty and the cover is closed.
5. Set the display mode to TRANSMITTANCE by pressing the MODE control key until the appropriate LED is lit.
6. Fill a clean cell with water and wipe the cell with a tissue (KimwipeTM) to remove liquid droplets, dust and fingerprints.
7. Place the cell in the sample compartment and align the guide mark on the cell with the guide mark at the front of the sample compartment. Press the cell firmly into the sample compartment and close the lid.
8. Carefully adjust the display to 100%T with the Transmittance/Absorbance Control (9). Move the knob slowly as you approach 100%T.
9. Remove the cell from the sample compartment and empty the water.
10. Rinse the cell twice with small volumes of the solution to be measured and fill it with the solution.
11. Wipe the cell with a tissue and insert the cell into the sample compartment. Align the guide marks and close the lid.
12. Read the appropriate value (%T) from the display.
13. Remove the cell from the sample compartment and repeat steps 10 through 12 for any remaining sample solutions.
14. When all measurements are completed, turn off the spectrophotometer by turning the Power Switch counterclockwise until it clicks.
Step 4. Using solution no. 1, follow the directions for instrument operation and record (%) transmittance values for each wavelength in Table 2.
Remember to reset the instrument to 100% for each wavelength investigated.
DO NOT DISCARD THIS SOLUTION,
Step 5. The wavelength that gives the largest absorbance value will provide the greatest sensitivity to concentration change. Generate an Excel graph of wavelength (x) vs. absorbance (y) using these values. At zero absorbance, there isnât any CoCl2 so donât forget to include the (0,0) data point. Connect your data points with a smooth curve. This is the absorption spectrum of aqueous CoCl2. Submit this with your lab report.
Step 6. Reset your spectrometer using this wavelength (step 5), and measure this solution and the other six solutions listed in Table 1, and record your % transmittance values in Table 3.
TABLE 2
Wavelength (nm) | % Transmittance | Absorbance |
400 | ||
425 | ||
450 | ||
475 | ||
500 | ||
525 | ||
550 | ||
575 | ||
600 |
MAXIMUM ABSORBANCE IS LOCATED AT ________________nm.
TABLE 3 -Results measured at ______nm.
Test tube No. | % Transmittance | Absorbance | Molarity(M) |
1 | |||
2 | |||
3 | |||
4 | |||
5 | |||
6 | |||
7 |
Step 7. Plot a graph of Molarity (M) vs. Absorbance for all seven solutions using Excel plotting techniques. This is called a calibration curve, whereby one establishes a measured response to a known solution concentration. Determine the slope of the line and include the linear equation of fit, and the correlation coefficient.
Recall the relationship A = kC or y = mx + b; where b is the (0,0) data point
Then: k = A/C
Step 8. The unknown solution to be analyzed is more concentrated than any of the standard solution concentrations that were measured to prepare the calibration curve.
Points to consider:
You must achieve a dilution such that the absorbance is within the absorbance range of the standards that were previously measured.
By using serial dilutions, will multiply many errors; thus it is best to obtain a dilution is one-step if possible.
Consider reducing the concentration by ¾, or by ½, and by ¼ or to 0.10 of the original concentration and test the solution to see if the absorbance response is within range. You may also consider using the dilutions in Table 1. Once this is determined, proceed to the next step. Complete the dilution table for the diluted concentrations you prepared:
Trial | mL of unknown | mL of water | (%T) | A |
1 | ||||
2 | ||||
3 |
Step 9. Using the desired dilutions, determined in step 8, measure two of the diluted solutions and record the measured transmittances in Table 4.
UNKNOWN NUMBER __________
TABLE 4
Diluted concentration (M) | Transmittance (%T) | Absorbance (A) |
Calculation of absorbance, for diluted Unknown solution:
Step 10. Determine the concentration of the diluted solution using the linear equation of fit, knowing the absorbance and k, the slope of the line.
C = A/ k
Step 11: Determine the concentration in your original Unknown solution. Show your
back-calculation below to support your final answer to this experiment.
Calculations:
Unknown Solution No. ________ Concentration: ___________M
Prelab Questions
1. Consider a solution of 0.400M Co(NO3)2 provided by your lab instructor.
You are required to make the following dilute concentrations:
0.160M and 0.240M solutions. You are provided the following glassware: 5.0 mL Mohr pipet and 18 mm x 150 mm test tubes. Describe how you would prepare each solution, and support your description with your calculations. (Recall (Mc x Vc = Md x Vd) where Mc is the molarity of the concentrated solution, Vc is the volume of the concentrated solution, Md is the molarity of the dilute solution, and Vd is the volume of the diluted solution.)
Given 0.400 M Co(NO3)2 solution.
Lets say we pipette out 5 mL of this solution and dilute it to get 0.160 M solution. Then
Using, Mc x Vc = Md x Vd
0.400 x 5 = 0.160 x Vd or Vd= (0.400 x 5)/0.160 = 12.5 mL
Thus we need to add 7.5mL distilled water to 5 mL of cobalt nitrate. Since we are only provided with a 5 mL pipette, we can only measure out volumes in multiple of 5.
thus pipette out (5 x 2) 10 mL of cobalt nitrate solution in the test tube and dilute it by addition of (7.5 x2) 15 mL of distilled water.
Again for preparing 0.240 M solution
Lets say we pipette out 5 mL of this solution and dilute it to get 0.160 M solution. Then
Using, Mc x Vc = Md x Vd
0.400 x 5 = 0.240 x Vd or Vd= (0.400 x 5)/0.240 = 8.33 mL
Thus we need to add 3.33mL distilled water to 5 mL of cobalt nitrate. Again taking volumes only in multiples of 5, pipette out (5 x 3) 15 mL of cobalt nitrate solution in the test tube and dilute it by addition of (3.33 x3) 10 mL of distilled water.
2. In your own words, explain, in detail, what you will be learning during this lab. Address the chemical principles and, laboratory skills, in your answer.
Post - Lab Questions:
a) Letâs say, for a given concentration of salt solution, the maximum response at a wavelength maximum of 485nm, is 0.750. If an unknown solution is analyzed at a longer or shorter wavelength would the investigator obtain the same concentration for the Unknown solution? Explain why.
b) List all possible sources of errors that may result in this experiment.