COMP10001 Final: INFO.Method list and functions
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Related Questions
1. Apply to actual companies the basic knowledge and analytical techniques learned from our course.
2. Prepare common-size financial statements, comparative financial statements, and various profitability and risk ratios.
3. Compare the calculated results with competitors and across different years.
4. Summarize the analyses and make investment recommendations.
You will be analyzing the following firms:
Williams-Sonoma, Inc.
Pier 1 Imports, Inc.
For these firms, download the most recent annual report (10-K report) to begin your work. In 10-K reports, you can find companiesâ basic information, financial statements, footnotes to the financials, and the management discussions and analyses. Please download the 10-K reports from the following web links:
10-K reports (fiscal year 2016) for Williams-Sonoma, Inc.
https://www.sec.gov/Archives/edgar/data/719955/000119312517104341/d265187d10k.htm
10-K reports (fiscal year 2015) for Williams-Sonoma, Inc.
https://www.sec.gov/Archives/edgar/data/719955/000119312516525847/d120289d10k.htm
10-K reports (fiscal year 2014) for Williams-Sonoma, Inc.
https://www.sec.gov/Archives/edgar/data/719955/000119312515118009/d851953d10k.htm#tx851953_13
10-K reports (fiscal year 2016) for Pier 1 Imports, Inc.
https://www.sec.gov/Archives/edgar/data/278130/000119312517136345/d343458d10k.htm
10-K reports (fiscal year 2015) for Pier 1 Imports, Inc.
https://www.sec.gov/Archives/edgar/data/278130/000119312516556025/d133529d10k.htm
10-K reports (fiscal year 2014) for Pier 1 Imports, Inc.
https://www.sec.gov/Archives/edgar/data/278130/000119312515153179/d881010d10k.htm#toc881010_13
For your convenience, I also provided the balance sheet and income statement of each company for the most recent years at the end (page 5-8; Table 1-4). Please use them to prepare common-size financial statements and comparative financial statements.
Guidance
The required tasks are detailed below:
(1) Prepare common-size balance sheets and income statements for both companies. Note: Compute for the most recent THREE years.
(2) Prepare comparative analysis (i.e., change of percentage analysis) on income statement and balance sheet for both companies. You should compute for the most recent THREE years.
(3) Prepare ratio analyses (for the same THREE year time period) for both companies. At least, you should include the following ratios in your computations: (1) current ratio, (2) acid-test ratio, (3) receivables turnover, (4) inventory turnover, (5) asset turnover, (6) profit margin on sales, (7) rate of return on assets, (8) rate of return on common stock equity, (9) earnings per share, (10) payout ratio, (11) debt to total assets ratio, (12) times interest earned, (13) cash debt coverage ratio, and (14) book value per share.
(4) Comment on the analytical results of the two companies. Your comments should concentrate on the trends across the companies. In addition to contrasting the ratios between the companies, you should interpret the numbers and make suggestions as to why the ratio of one company might be higher/lower than the other.
(5) Write a conclusive summary on the firms you have studied. Based upon your conclusions, recommend the better performing firm for potential investment. Your conclusions should be based upon, and specifically reference, the analyses prepared in this report.
(6) Read sample project to get some ideas.
Report Format Requirements:
A. Report body requirements:
Cover page. List the title of the project, your names, and semester/year.
Abstract or Executive Summary. This is a separate page. It should cover the purpose of the project, the major findings, and the conclusions/recommendations, in summary form.
Table of Contents.
Main body. Use the following sequence for report content:
Introduction to the two companies and to the purpose of the report
Analytical section. This should include all your numerical analyses. This is where you will discuss the results of, comments on, and conclusions about the vertical and horizontal common-size statements, comparative analysis (i.e., change of percentage analysis), and the ratio analyses for both companies.
Comparisons of companies and all other analysis (observations and/or interpretations). (You may combine b and c if you wish, as long as both are well covered.)
Conclusions and recommendation for investment.
References. List all major reference sources.
Appendices. Include tables and graphs of your numerical analyses. For reference convenience, assign a title to each separate item, such as Table 1, Exhibit 1, etc.
B. Typesetting requirements:
Use size 12 font. Times New Roman is preferred.
Double space between lines.
Number pages in accordance with the APA style guide.
One inch on all sides.
Do not right justify text. Use left justify.
Minimum length: 8 pages. (Note: You can easily meet the minimum length requirement since you will have a lot of tables in the paper.)
The submitted work should be in ONE file with a word or pdf format. An Excel spreadsheet file is NOT acceptable.
Plagiarism
Plagiarism will not be tolerated. Evidence of plagiarism will result in a grade of âFâ to the course and be subject to appropriate disciplines.
NOTES:
A portion of your grade will be assessed based on the overall report quality, clarity, format, and cohesiveness.
A FREE RIDER in the group will not be tolerated. However, to report an alleged free rider, you should send me a formal written complaint. You should carefully manage your group over the semester to ensure that no teammate will take the chance of turning into a free rider. Try to contact/manage your teammates frequently and inform me if any member is not willing to participate the group work so we can address this issue ASAP. A free rider will receive his/her group project grades solely based on what he/she has contributed to the projects. If there is a free-rider in your group or a member drops the class, the rest of the group members are still expected to submit a COMPLETE paper.
Again, the balance sheet and income statements are provided at the end. Please use them to prepare common-size and comparative financial statements.
Table 1. Williams-Sonoma, Inc ----Balance Sheet
Williams-Sonoma, Inc. | ||||
BALANCE SHEET | ||||
Fiscal Years 2016, 2015, 2014, 2013 | ||||
(In thousands) | FY 2016 | FY 2015 | FY 2014 | FY 2013 |
ASSETS | ||||
Current assets | ||||
Cash and cash equivalents | $ 213,713 | $ 193,647 | $ 222,927 | 330121 |
Restricted cash | â | â | â | 14289 |
Accounts receivable, net | 88,803 | 79,304 | 67,465 | 60,330 |
Merchandise inventories, net | 977,505 | 978,138 | 887,701 | 813,160 |
Prepaid catalog expenses | 23,625 | 28,919 | 33,942 | 33,556 |
Prepaid expenses | 52,882 | 44,654 | 36,265 | 35,309 |
Deferred income taxes, net | â | â | 130,618 | 121,486 |
Other assets | 10,652 | 11,438 | 13,005 | 10,852 |
Total current assets | 1,367,180 | 1,336,100 | 1,391,923 | 1,419,103 |
Property and equipment, net | 923,283 | 886,813 | 883,012 | 849,293 |
Deferred income taxes, net | 135,238 | 141,784 | 4,265 | 13,824 |
Other assets, net | 51,178 | 52,730 | 51,077 | 54,514 |
Total assets | $ 2,476,879 | $ 2,417,427 | $ 2,330,277 | 2,336,734 |
LIABILITIES AND STOCKHOLDERSâ EQUITY | ||||
Current liabilities | ||||
Accounts payable | $ 453,710 | $ 447,412 | $ 397,037 | 404791 |
Accrued salaries, benefits and other liabilities | 130,187 | 127,122 | 136,012 | 138,181 |
Customer deposits | 294,276 | 296,827 | 261,679 | 228,193 |
Income taxes payable | 23,245 | 67,052 | 32,488 | 49,365 |
Current portion of long-term debt | â | â | 1,968 | 1,785 |
Other liabilities | 59,838 | 58,014 | 46,764 | 38,781 |
Total current liabilities | 961,256 | 996,427 | 875,948 | 861,096 |
Deferred rent and lease incentives | 196,188 | 173,061 | 166,925 | 157,856 |
Long-term debt | 1,968 | |||
Other long-term obligations | 71,215 | 49,713 | 62,698 | 59,812 |
Total liabilities | 1,228,659 | 1,219,201 | 1,105,571 | 1,080,732 |
Stockholdersâ equity | ||||
Preferred stock: $.01 par value; 7,500 shares authorized; none issued | â | â | â | 0 |
Common stock: $.01 par value; 253,125 shares authorized; | ||||
87,325 and 89,563 shares issued and outstanding at | 873 | 896 | 919 | 941 |
January 29, 2017 and January 31, 2016, respectively | ||||
Additional paid-in capital | 556,928 | 541,307 | 527,261 | 522,595 |
Retained earnings | 701,702 | 668,545 | 701,214 | 729,043 |
Accumulated other comprehensive loss | (9,903) | (10,616) | (2,548) | 6524 |
Treasury stock â at cost: 20 and 29 shares as of January 29, 2017 and January 31, 2016, respectively | (1,380) | (1,906) | (2,140) | (3,101) |
Total stockholdersâ equity | 1,248,220 | 1,198,226 | 1,224,706 | 1,256,002 |
Total liabilities and stockholdersâ equity | $ 2,476,879 | $ 2,417,427 | $ 2,330,277 | 2,336,734 |
Table 2. Williams-Sonoma, Inc --- Statement of Income
Williams-Sonoma, Inc. | ||||
STATEMENT OF INCOME | ||||
Fiscal Years 2016, 2015, 2014,2013 | ||||
(In thousands) | FY 2016 | FY 2015 | FY 2014 | FY 2013 |
E-commerce net revenues | $ 2,633,602 | $ 2,522,580 | $ 2,370,694 | $ 2,115,022 |
Retail net revenues | 2,450,210 | 2,453,510 | 2,328,025 | 2,272,867 |
Net revenues | 5,083,812 | 4,976,090 | 4,698,719 | 4,387,889 |
Cost of goods sold | 3,200,502 | 3,131,876 | 2,898,215 | 2,683,673 |
Gross profit | 1,883,310 | 1,844,214 | 1,800,504 | 1,704,216 |
Selling, general and administrative expenses | 1,410,711 | 1,355,580 | 1,298,239 | 1,252,118 |
Operating income | 472,599 | 488,634 | 502,265 | 452,098 |
Interest (income) expense, net | 688 | 627 | 62 | (584) |
Earnings before income taxes | 471,911 | 488,007 | 502,203 | 452,682 |
Income taxes | 166,524 | 177,939 | 193,349 | 173,780 |
Net earnings | $ 305,387 | $ 310,068 | $ 308,854 | $ 278,902 |
PLEASE HELP ME ANSWER THE POST LAB QUESTIONS. I did THE PRE LAB. I ALSO FILLED in the tables.
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 Switchcounterclockwise 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 | 88.3 | 0.055 |
425 | 73.7 | 0.132 |
450 | 43.6 | 0.362 |
475 | 23.8 | 0.623 |
500 | 15.7 | 0.804 |
525 | 16.0 | 0.797 |
550 | 38.9 | 0.410 |
575 | 73.0 | 0.37 |
600 | 85.3 | 0.069 |
MAXIMUM ABSORBANCE IS LOCATED AT __________500______nm.
TABLE 3 -Results measured at _500_____nm.
Test tube No. | % Transmittance | Absorbance | Molarity(M) |
1 | 15.8 | 0.802 | |
2 | 22.8 | 0.643 | |
3 | 27.4 | 0.562 | |
4 | 33.1 | 0.480 | |
5 | 40.2 | 0.396 | |
6 | 47.6 | 0.323 | |
7 | 69.3 | 0.159 |
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 | 51.9 | 0.284 | ||
2 | 70.7 | 0.151 | ||
3 | 79.3 | 0.101 |
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 _____B_____
TABLE 4
Diluted concentration (M) | Transmittance (%T) | Absorbance (A) |
Pure unknown B | 8.7 | 1.062 |
1 mL of unknown in 1 mL of water | 29.5 | 0.531 |
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:
If needed I did a graph slope and got y= 0.1896x
R^2=0.9951
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.
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.