University of Toronto Faculty of Applied Science and Engineering
Technical Report — Assignment 3 Prepared by: Group 12 Mariam Itani, Johnny McRae, Miko Samson, Jeslyn Lorraine Winoto
External Site Sample
G1
Internal Site Sample
I3
Course: CHE204 Instructor: Prof. Farmer Assignment: Methodology The University of Toronto and the Faculty of Applied Science and Engineering take academic integrity very seriously. The Code of Behaviour on Academic Matters provides details of what is considered an academic offence, and the possible consequences if you are found to have committed an offence. All academic work must be conducted in full accordance with the rules and regulations of the University. As a student, you are responsible for ensuring the integrity of your work and for understanding what constitutes an academic offence. Resources are available to students to support them in understanding and preventing academic offenses. University of Toronto Academic Integrity: https://www.academicintegrity.utoronto.ca/ Engineering Communication Centre Tutoring Program: https://ecp.engineering.utoronto.ca/ecp-tutoring-centre/
Academic Integrity Statement Complete the following declaration, and return it with your assignment. By signing this statement, I hereby state that I have reviewed not only my work, but the work of my colleagues, in its entirety and have not committed any of the following academic offences as laid out in The Code of Behaviour on Academic Matters: a)
Falsified or concocted any evidence, data, or sources used to complete this assignment,
b) Obtained unauthorised assistance to complete this assignment, including having someone else complete this assignment on my behalf, c)
Represented the work or ideas of others as my own, or
d)
Submitted academic work which I have previously submitted for credit at the University or elsewhere.
I recognize that academic offences are extremely serious and constitute unacceptable behaviour at the University of Toronto. They are a breach of ethical standards of the engineering profession that I aspire to enter.
Name: Miko Samson, Signature: Name: Jeslyn Lorraine Winoto, Signature:
, Date: 12/06/2023 , Date: 12/06/2023
Name: Mariam Itani Signature:
Date: 12/06/2023
Name:Johnny McRae Signature:
Date: 12/06/202
Executive Summary Upon request from Vale ltd., the Wallberg Corporation has conducted analysis of the copper concentrations of Copper Cliff South Mine (of Vale ltd.) and Champion Iron Mine in order to provide a justified recommendation as to which mine to purchase ore from. The process of analysis was done on 5g of Copper (II) Oxide samples taken from both sites that were analyzed through complexation titration and spectrophotometry. Factors outside of concentration were also factored into the recommendation provided, such as sociopolitical, economic and environmental factors.
Methodology By dissolving both 5g samples of copper (II) oxide in sulfuric acid we were able to produce solutions of aqueous copper sulfate. Through complexometric titration of each sample with EDTA triplicate results helped us to determine the concentration of both samples with confidence. The solutions were also run through a uv-vis spectrometer which allowed us to measure the absorbance of each sample and therefore determine the concentration yielded from the spectrometry.
Results and Recommendation Using complexometric titration we determined the copper purity to be 16. 21% ± 0. 43% for the Copper Cliff South Mine and 17. 55% ± 0. 43% for Champion Iron Mine. Spectroscopy results were calculated through the generation of a calibration curve with standard solutions. After subbing in the absorbances read by the spectrometer the concentration calculated were 2. 2 ± 0. 3% for Copper Cliff South Mine and 2. 0 ± 0. 3% for Champion Iron Mine. These results vary significantly although we were able to identify issues in the spectrophotometry process that was undergone and therefore rely on the titration results in our recommendation. While the Champion Iron Mine has a slightly less reputable work life experience for its employees it is positively involved with its neighboring indigenous community and commits to operating itself in a sustainable manner.
Its superior copper concentration as well as its
impressive performance in the previously mentioned fields is why we would recommend Vale ltd. externally purchases copper units from Champion Iron Mine.
1.0 Introduction This report explains the findings of a quantitative comparison of Copper concentrations between Vale Ltd’s Copper Cliff South Mine, internal and Champion Iron Mine, external. Copper (II) Oxide samples were taken from both sites. Then, Copper in each sample was extracted and both sites’ samples were analyzed through complexometric titration and spectrophotometry, due to the current problems with the ICP (Inductively Coupled Plasma) machine. Through these techniques, the concentration of Copper at each site would be determined allowing for an educated recommendation supported by chemical analysis on which site yields more Copper in its ore. This recommendation is to be used by Vale Ltd. to determine which site they would purchase copper concentrates from to use for processing at the Long Harbor Processing Plant. The extraction of metal oxides with an acid is known as leaching. Through leaching, a metal oxide reacts with an acid to form salt and water. This allows for a solution of the aqueous salt to be produced, permitting easier chemical analysis of the concentration of the metal present in the oxide. The typical chemical reaction between a metal oxide and an acid is represented in Figure 1 below. This reaction can also be looked at as a neutralization reaction. This is because metal oxides are basic.
[1] Figure 1. General chemical reaction of metal oxide reaction with acid. For this experiment, the leaching took place with Copper (II) Oxide and Sulfuric Acid. This produces a cyan-blue solution of aqueous Copper Sulfate that was used for the complexometric titration and spectrophotometric analysis. The reaction that occurs can be seen in Figure 2 belo w.
Figure 2. The chemical reaction of copper (II) sulfate with sulfuric acid.
Analysis by complexometric titration was performed on these copper sulfate solutions. This process is mainly used for determining concentrations of metal ions present in a solution through complex-forming reactions most widely using a titrant of EDTA (Ethylenediaminetetraacetic acid) to rapidly form water-soluble, stable complexes with the metal. The 1:1 stoichiometric ratio of EDTA to the complex allows for convenient titration. This reaction generates hydrogen ions which require the assistance of a pH buffer to regulate acidity levels.
[2] Figure 3. General chemical reaction of a metal ion with EDTA (H4Y). Most commonly, an organic dye is used as a color indicator for complexometric titrations. For this experiment, murexide was used. The organic dye attaches to the metal ion and as the EDTA replaces the organic dye the color change becomes noticeable. The color change will indicate the end point of the titration and with knowledge of the titrant concentration and analyte volume, the volume of EDTA titrated can be used to calculate the concentration of the metal in the solution. The other form of analysis used is spectrophotometry in which concentration levels are ascertained through observation of the absorbance of light of a solution. In this experiment, the spectrophotometry was done with a UV-Vis spectrometer. This machine emits light within the UV and visible spectrums and then measures the amount of light absorbed by or transmitted through the sample.
[3] Figure 4. Visualization of the way the spectrophotometer operates. Using the Beer-Lambert equation the absorbance along with the molar absorptivity and path length of the concentration of your sample can be calculated.
[5] Figure 5. Beer-Lambert law equation. The processes of complexometric titration and spectrophotometry both yield concentrations of solutions with unknown concentrations. Although it may seem redundant the use of both processes allows for the verification of results. When comparing the two techniques it can be speculated that a spectrophotometer would be more accurate than complexometric titration. The main reason is that complexometric titration can incorporate an amount of human error because recognition of endpoint based on color change viewed by the naked eye is not an exact science, especially when compared to the accuracy of spectrometers at reading absorbances.
2.0 Methodology The methodology is split up into 3 major parts: the extraction, the complexometric titration and the spectroscopy. The equipment required with the safety and hazard information for each part can be found in Appendix A. The following is an overview of the procedure for each of the parts, and the detailed step-by-step procedure for each section can be found in Appendix B.
2.1 Extraction First, the glassware and associated equipment were cleaned, leaving ample time to let them dry to not skew results. Then 5g of each sample were measured and put into the cleaned and dry flasks. Recorded measurements are in Appendix C.1.0. After appropriate labeling, 25 mL of H2SO4 was pipetted into each beaker. Next, each beaker was transferred to a hot plate to heat setting 3 and stir setting 3. The external sample, G1, took about 10 minutes to dissolve, whereas the internal sample, I3, took 2 hours. The external sample was not dissolving for the first hour, then with the addition of 25 mL of H2SO4, the process accelerated. This may have potentially altered results for the absorbances.
Once each sample was dissolved, they were transported to a 100 mL volumetric flask and diluted.
2.2 Complexometric Titration All equipment and glassware required were cleaned. Then, 50 mL of the stock copper sulfate standard was diluted 5-fold and labeled solution B. 10 mL of solution B was added to an Erlenmeyer flask alongside 10 drops of murexide and 3 drops of pH 10 buffer. After this was then titrated with the EDTA and repeated 3 more times. All initial and final volumes were recorded and are found in Appendix C.2.0. Lastly, 10 mL of both site solutions were pipetted into cleaned and dried 125 mL Erlenmeyer flasks, prepared with 10 drops of murexide and 3 drops of pH 10 buffer, and titrated. All respective measurements are also found in Appendix C.2.0.
2.3 Spectroscopy Initially, the team started by preparing six 100 mL solutions of varying concentrations of the copper (II) standard sulfate solution, with each containing 5 mL of 5M NH4OH. Then, the blank solution was prepared, containing 5 mL of 5M NH4OH with the remaining volume filled with distilled water in a 100 mL volumetric flask. Next, the solution in the middle of the range of the concentrations of the six solutions was selected (25 mL) and prepared, then used to fill one cuvette three-quarters full. Then, this process was repeated with the blank solution. The lambda max was then determined using the UV-Vis spectrophotometer (Appendix C.3). The Spec 20 was set to the desired wavelength, the lambda max, and calibrated. Triplicate readings for each of the six solutions were taken. If discrepancies arose, a fourth reading was taken. Lastly, three solutions of varying concentrations for the two sites were prepared by varying the quantity of the site’s stock solution added to 5 mL of 5M NH4OH in a 100 mL volumetric flask filled to the mark with distilled water. For each of these solutions, triplicate absorbance readings were taken using the same Spec 20. A 4th reading was also taken if there was a large discrepancy between readings.
3.0 Results The following section details the calculations, summary of experiment results, error deviations, and experimental observations obtained during the conducted experiments.
3.1 Extraction Qualitatively it should be noted that sample I3 took about 2 hours to dissolve compared to sample G1. 25 mL of H2SO4 was added to the I3 solution to accelerate the process.
3.2 Complexometric Titration Complexometric titration deduced that the copper compositions in each sample were 16. 21% ± 0. 43% for G1, internal, and 17. 55% ± 0. 43% for I3, external. The purity of the sample was determined by calculating the volume of the standardized EDTA needed to reach equivalence with 10 mL of the sample solution. Sequentially, the moles of copper and the molarity of the sample solution were calculated. Using the molarity and the total volume of the solution, the total moles of copper were calculated, which was then divided by the total weight of the sample. More detailed sample calculations and raw data are located in Appendix C.
3.3 Spectroscopy The weight percentage of the copper from the spectroscopy analysis was calculated with the use of a calibration curve. The calibration that was deemed best was the one only including the first three points as they are the most accurate and least susceptible to being outliers, giving a strong 2
𝑅 (Appendix C3.1). In addition, the solutions with 35 mL and 50 mL stock copper were not only very dark in color but their turbidity was very high due to the principate they were forming which would suspend in the liquid for a bit before separating shortly after, further reinforcing the unreliability of the results of these points. After setting up the calibration curve the concentrations in each sample were calculated using the linear best-fit line formula. From the concentrations of each of the 3 solutions prepared for each site, it was possible to calculate the weight percent and the average of them was the determined weight percentage for each site.
For the internal site, the weight percentage calculated was 2. 2 ± 0. 3% (Appendix C.3.2) while for the external one, the weight percentage calculated was 2. 0 ± 0. 3%.
4.0 Discussion The group’s recommendation considers various aspects of the background of the two mining sites: Copper Cliff South Mine (Internal) and Champion Iron Mine (External). These factors include sociopolitical, economic, and environmental considerations, along with the calculated weight percentage of copper extracted from laboratory testing.
4.1 Sociopolitical 4.1.1 Community Engagement and Stakeholder Relationships Both Vale’s Ontario Operations and Champion Iron Mine demonstrate a commitment to engage with Indigenous communities and foster community relationships. Vale’s Ontario Operations focuses on establishing signed agreements and Impact Benefit Agreements with multiple First Nations and Metis groups within the Sudbury Basin [6]. Conversely, Champion Iron’s efforts include a broader spectrum of initiatives, such as cultural workshops, partnerships, scholarships, and diverse community engagements, aiming for inclusivity, cultural recognition, and social welfare support [6]. Furthermore, both companies adhere to the tailing management governance model and framework set by the Mining Association of Canada (MAC). They also actively participate in industry associations like the Canadian Dam Association.
4.1.2 Employee Work Life The work-life experience of employees at Vale and Champion Iron is important to consider when ensuring the ethical practice of a company's spending. Supporting a company that mistreats its employees is both immoral and not in the best interest of the purchasing company. Organizations like Zippio and Indeed use employee experience to grade companies on their work-life experience, this information can be used to help in the recommendation. Indeed the work life at Vale is 4.3 / 5.0 noting great benefits as well as a good workplace culture. Zippia has given Champion Iron Mine a 3.8/5.0 with no genuine comments on employees' experience. While Vale seems to provide a better work-life experience from the surface view this slight discrepancy is
not significant in the recommendation to be made for purchasing copper units from either company.
4.2 Economic The price of purchase for the two mines is not available to the public, however, there is a standardized metric for the cash cost of running a mining operation in the copper mining industry. The metric is known as C1 costs and its specific purpose is for comparison across the industry. While this cost will not perfectly correlate to the price of purchase of ores from these mines it is reasonable to assume that their cost of production would be relative to their price of purchase. In 2021, S&P Global Inc. did a rating snapshot of Vale Ltd. and determined that their C1 cost was $15-17/DMT of ore (USD/dry metric tonne). In contrast, Champion Iron Mines' annual report from 2023 outlines their C1 cash cost of $73.9/DMT of ore sold. This means that the C1 cost of Champion Iron Mines is approximately 462% of the Vale Ltd. The drawback of this data is that the price of the ore cannot be determined because that information is not public and these values are not specific to individual sites but rather to the companies as a whole. This is because C1 costs are usually used as a marker for a company's cost efficiency in production. This difference in C1 cost could be a result of Champion Iron Mines ore being more concentrated with copper causing a more expensive refinery process. C1 costs alone do not determine the superiority of ore to purchase, however, they do provide valuable insight.
4.3 Environmental 4.3.1 Water Management The water management system at Copper Cliff Mine (Vale) [6] encompasses sub-watersheds, reservoirs, and treatment facilities like the Copper Cliff wastewater treatment plant, which recycles the flows for mill process water. Storage reservoirs manage water during peak flow, while mine water and surface waters undergo treatment at the west surge pond using hydroxide precipitation, settling, and filtration. The treated water is primarily utilized in mine processes. Similarly, Champion Iron Mine emphasizes water recycling to minimize its impact on water resources and maximize efficiency. The company employs diverse strategies, including groundwater dewatering, precipitation collection, and active monitoring of water inputs and
outputs to minimize hydrological losses and optimize water use in the mining process. This resulted in a remarkable 96% utilization of recycled water [7].
4.3.2 Tailing Management and Land Rehabilitation The Copper Cliff Central Tailing Area (CTA) covers a vast area of approximately 35 km2, with a portion of 50% reclaimed [8]. Due to its urban setting and the presence of a large volume of impounded tailings and process water, the CTA’s tailing containment is managed as high-consequence dams. The estimated 932 million tons of tailings anticipated to be contained within the CTA pose environmental concerns due to the highly reactive nature of the pyrrhotite tailings produced by Vale, requiring perimeter containment dams using rock tailings to prevent acid rock drainage and metal leaching. On the other hand, Champion Iron, despite reclaiming a smaller land area (74.2 hectares) [9], demonstrates advanced tailings management practices. Champion Iron adopts a strategy of segregating mine tailings into distinct categories: fine tailings(slit-clay) and coarse tailings(sand). This separation enables customized management approaches based on specific characteristics of each type. Furthermore, the company benefits from a robust and secure foundation due to its operational presence in the geologically stable Canadian Shield region. Therefore, Champion Iron’s focused tailings management strategies suggest a higher level of environmental responsibility and potential mitigation of environmental impacts compared to the CTA’s practices.
4.4 Laboratory Analysis and Copper Content The laboratory gave conflicting results. The titration analysis indicated that the external is more concentrated while the spectroscopy analysis indicated that the internal site is more concentrated. While analyzing what went on in the lab, the external site required a lot more sulfuric acid to fully dissolve all the copper. This is in favor of the external site having more copper as if more is required to fully dissolve this means the sulfuric acid was limiting indicating that there was more undissolved copper while for the internal site the same amount of sulfuric acid was enough and hence was not limiting. As apparatus are susceptible to multiple sources of error from calibration to malfunctioning, it is more reliable to consider the titration data as an accurate representation of the trend because it
follows the trend shown based on the chemical reaction that occurs when extracting which is the least susceptible to error. In addition, upon further analysis of the comparison to the actual values from the sites, the values obtained by the titration were far closer to the ones obtained by the spectroscopy analysis. Therefore, in terms of which site would give a higher percentage of copper per amount mined, the external site is favorable.
5.0 Conclusion and Recommendation Ultimately the external site, Champion Iron Mine, is the professional recommendation of the Lash Miller scientist. Despite its higher C1 costs and comparatively shorter work life score, Champion Iron excels in several crucial aspects. With ores that are 1.34% purer, commendable water and tailing management practices, active engagement with the Indigenous community, robust sustainability efforts, and transparent disclosure about their operational processes to the public, the site emerges as a superior choice. Notably, neither the site nor the company presents any significant issues that overshadow these mentioned qualities. Looking ahead, the next steps following this recommendation involve using this analysis as a foundation for deeper exploration. This includes conducting a comprehensive evaluation of alternative mining sites and engaging in discussions with industry experts and local communities. These steps aim to enhance our understanding and refine the evaluation framework. This lab experience has taught us the importance of critical thinking, first and second-hand research, as well as considering multiple factors before arriving at a conclusion. These skills are pivotal in the industry,where decisions can wield extensive influence on a diverse array of stakeholders,both internal and external. Consequently, it becomes imperative to weigh STEEPLE factors (social, technological, economic, environmental, political, legal, and ethical threats) alongside the company’s individual benefits.
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Appendix A A.1 Instrumentation The instrumentation required is split up into the 3 major parts of the experiment: Extraction, Complexometric Titration, and Spectroscopy.
A.11 Extraction
A.12 Titration
A.13 Spectroscopy
2x 125 mL Erlenmeyer Flask
1x , 250 mL Volumetric Flask
2x 100 mL Volumetric Flask
2x 100 mL Volumetric Flask
1x Volumetric Flask Stopper
2x Volumetric Flask Stopper 1x Wash Bottle 1x Watch glass 1x 400 mL Beaker (Waste) 2x 100 mL Beaker
1x 1 mL Volumetric Pipette
1x Wash Bottle
1x 5mL Volumetric Pipette 1x Watch glass
1x 10 mL Volumetric Pipette
1x 400 mL Beaker (Waste)
1x Pipette bulb
1x 25 mL Volumetric Pipette
1x 50mL Burette
2x Pipette Bulb
1x Retort Stand
1x 10 mL Graduated Cylinder
1x Butterfly clamp
2x Wash Bottle
1x 50 mL Beaker 1x 25 mL Volumetric Pipette
2x Volumetric Flask Stopper
1x
White
Titration 2x Plastic Cuvette
Background
1x Watch glass
3x 125 mL Erlenmeyer flask
4x Test tubes
1x Reading Card
1x Test tube Rack
1x Funnel
2x Dropper
2x Stir Rod 2x Hot plate
7x 125 mL Erlenmeyer flask 1x 400 mL Beaker (Waste) UV-Vis Spectrophotometer Spec 20
A.2 Instrumentation Uncertainties Table 1. Instrumentation and their associated uncertainties. Instrumentation
Uncertainty
1 mL Volumetric Pipette
± 0. 012𝑚𝐿
5mL Volumetric Pipette
± 0. 02𝑚𝐿
10 mL Volumetric Pipette
± 0. 02𝑚𝐿
25 mL Volumetric Pipette
± 0. 06𝑚𝐿
100 mL Volumetric Flask
± 0. 08𝑚𝐿
250 mL Volumetric Flask
± 0. 12𝑚𝐿
50 mL Burette
± 0. 05𝑚𝐿
Analytical Balance
± 0. 001𝑔
Spec 20 Uncertainty
± 0. 001𝐴𝑢
A.3 Equipment Safety Table 2. Equipment Hazard and Safety. Equipment Glasswear
Hazard Can cause lacerations
Safety cuts
/ Inspect for any cracks or contamination (Dispose or wash if it is)
Exposure to Don’t cause rapid temperature changes to it contaminated chemicals and vent if temperature change occurs [10] Vent if a change of pressure occurs Wear safety glasses in case of broken glass [10] UV-Vis Spectrophotometer
Eye damage if looked Do not open the lid when renewing the into the light equipment Possible electric shock Possible burn [11]
Do not perform any maintenance and make sure all the wiring is proper
Equipment
Hazard
Safety Do not touch the machine when operating as it heats [11]
Spec 20
Possible burn
Do not perform any maintenance and make sure all the wiring is proper
Possible electric shock [12] Do not touch the machine and lamp when operating as it heats up [12]
A.3 Chemical List The chemicals required are split up by the 3 major parts of the experiment: Extraction, Complexometric Titration, and Spectroscopy.
A.31 Extraction
A.32 Titration
A.33 Spectroscopy
~ 5g Copper Oxide from each ~ 100 mL of Copper Sulfate site Standard Solution 0. 1518 ± 0. 0002 𝑀 ~ 75 mL of 1 M Sulfuric Acid ~ 400 mL of 0.05 M Distilled Water Ethylenediaminetetraacetic Acid (EDTA)
~ 200 mL of Copper Sulfate Standard solution 0. 1518 ± 0. 0002 𝑀 ~ 80 mL of 5M Ammonium Hydroxide Distilled Water
~ 20 mL of Murexide ~ 10 mL of pH 10 Buffer Distilled Water
A.4 Chemical’s Properties Table 3. List of the Chemicals Properties Name Copper Sulfate
Formula 𝐶𝑢𝑆𝑂4
Molecular weight
Melting Point
Boiling Point
159.61 g/mol 200℃ with 650℃ [13] decomposition [13] [13] or 590℃ (anhydrous) [13]
Physical Appearance White solid when Anhydrous, otherwise blue [13]
Name
Formula
Molecular weight
Melting Point
Ammonium Hydroxide
𝑁𝐻4𝑂𝐻
35.046 g/mol -58℃ [14] [14]
Distilled Water
𝐻2𝑂
Murexide
C8H8N6O6
Ethylenediam inetetraacetic Acid (EDTA) Sulphuric Acid Copper Oxide
Physical Appearance
(25%) -38℃ (25%) [14]
colorless aqueous solution [14]
18.015 g/mol 0℃ [15] [15]
100℃ [15]
Clear liquid [15]
284.19 g/mol 300℃ [17] [16]
443.25 ℃[17]
Purple-red solid with a green metallic luster [16]
𝐶10𝐻14𝑁2𝑁𝑎2𝑂8 336.21 g/mol 242℃ [18] [18]
N/A
White crystalline powder/ liquid, [18]
H2SO4
100℃ [19]
Clear, colorless, Liquid [19]
2000℃ [21]
Black [20]
(II) CuO
pH 10 Buffer
Boiling Point
98.08 [19]
g/mol 0℃ [19]
79.545 g/mol 1326℃ [20] [20]
Powder
Specific pH 10 buffer has not been provided
A.5 Chemical’s Safety Table 4. List of the Chemicals Hazard and Safety Name
Concentration
Amount
Hazard
Safety
Copper Sulfate Standard
0.1518 M +/0.0002 M
Approx. 300 mL
Irritant Environmental Hazard [13]
Limit exposure Wear PPE Work in a fume hood Dispose in the proper aqueous waste disposal Immediately neutralize the spillage using sodium bicarbonate and dispose of chemical waste disposal.
Ammonium Hydroxide
5M
5 mL per Corrosive 100 mL of Environmental solution Hazard [14] prepared
Dispose in the proper aqueous waste disposal Wear PPE Decrease concentration
Name
Concentration
Amount
Hazard
Distilled water
Pure
Specific amount unknown
Murexide
Unknown
10 drops each No Hazard [22] Erlenmeyer flask
Wear PPE. Avoid contact with skin, eyes or clothing, ingestion, inhalation, dust formation
Ethylenediamine 0.05 M tetraacetic Acid (EDTA)
Approx. 400 mL
Irritant Health Hazard [18]
Wear PPE. Do not breathe dust/ fumes/ vapor. Wash face, hands and any exposed skin thoroughly after handling. Rinse immediately if in contact.
pH 10 Buffer
Unknown
3 drops each Erlenmeyer flask
Acute toxicity and eye and skin irritation [23]
Immediately flush eyes and skin when exposed, Wear PPE. Use only in well-ventilated areas. Avoid breathing mists/vapors.
Sulphuric Acid
18M
100mL
Corrosive [19]
Wear PPE. Avoid contact with skin or eyes. Can cause skin burns and irritation When a spill occurs, sprinkle bicarbonate over the acid to neutralize. After neutralization, scoop the neutralized spill material and dispose of it in a designated chemical waste container.
5 g sample Environmental from each site Hazard [20]
Dispose in the proper waste disposal.
Copper Oxide
(II) N/A
No Hazard [15]
Safety No safety required
Appendix B This experiment consists of four primary segments: copper sample extraction, complexometric titration to determine the copper concentration, spectroscopy for identification, and clean up. Detailed steps are delineated for each section.
A.1 Extraction A.1.1 Preparation for Extraction 1. We obtained and weighed both 5 g site samples and deposited each in separate 125 mL Erlenmeyer flasks. Label each flask with their respective site. 2. Using a clean, dry 100 mL beaker, we measured ~ 75 mL of 1M Sulphuric Acid and labeled it stock Sulfuric Acid. 3. In a clean, dry 50 mL beaker we then measured ~ 25 mL of sulfuric acid 4. After, we rinsed a 25 mL volumetric pipette with distilled water first into a waste beaker and then three times with some sulphuric acid from the smaller beaker. Discard all of the remaining solution from the beaker. A.1.2 Preparation of Copper (II) sulfate Stock Solutions 1. We pipette 25mL of 1M Sulphuric Acid from the larger beaker into the G1 internal sample Erlenmeyer flask, and 50 mL into the external I3. containing the Copper (II) Oxide samples. Then, we swirled until all Copper (II) Oxide was dissolved. Please note that there will be undissolved impurities, this will be filtered in the next step. 2. Using a clean funnel, we carefully transferred all the Copper (II) sulfate solution from one Erlenmeyer flask to a 100 mL clean , dry volumetric flask. Then, we filled the mark with distilled water, and inverted until combined. 3. We then repeated step 2 for the other Copper (II) sulfate solution. Label both Volumetric Flasks Solution A, with their Site names and “Copper (II) sulfate”.
A.2 Complexometric titration A.2.1 Standardisation of the 0.05 M unstandardized EDTA solution 1. Using a rinsed volumetric pipette, we pipette 50 mL of the ~0.15 M stock Copper (II) sulfate standard. into a 250 mL volumetric flask. 2. Then, we dilute the solution with distilled water to the mark of the flask, cap, and invert to combine, labeling this “Solution B, CuSO4”. 3. We then add 10 mL of solution B into a 125 Erlenmeyer flask, repeating 2 times for 3 trials in total, labeling each trial. 4. Then, we obtain 200 mL of EDTA solution in a clean dry beaker. 5. We rinsed a 50 mL burette first with distilled water, and drained it into a waste beaker. Then rinsed with 0.05 EDTA (10-15 mL) three times. 6. We filled the rinsed 50 mL burette with EDTA, making sure that the burette is clamped vertically using a butterfly clamp into the retort stand and that there are no bubbles in the burette itself and the tip of the burette. Remove the funnel and drain until the meniscus lies at or below the 0 mL marking. 7. We recorded the initial reading of the 50 mL burette to two decimal places. Hold the reading card so that the dark line is about 1 cm below the meniscus. 8. We put a white titration background underneath the retort stand and placed one of the Erlenmeyer flasks containing Copper sulfate on it and started titrating with the EDTA. 9. Using our dominant hand, we swirled the flask and used our non-dominant hand to operate the burette tap, slowing the rate of addition as the endpoint approaches.he color should turn from light yellow to dark blue. 10. Repeat the titration two more times with the remaining two Solution B Erlenmeyer Flasks and record the final volume. A.2.2 Titration of Copper with EDTA 1. Pipette 10 mL of both site’s solution A into a clean dry 125 mL Erlenmeyer flask, repeat this three times for each site’s sample.
2. Add 10 drops of murexide to each Erlenmeyer flask containing the solution A. Ensure thorough mixing. 3. We added 3 drops of pH 10 buffer to each flask, and recorded the color of the solution. 4. Then, we titrated each sample with the standardized EDTA from section 3.2.1. Recorded the color changes and the initial and final volume readings on the burette using a reading card. The initial light yellow solution turned green near the endpoint and purplish blue at the endpoint. [14]
A.3 Spectroscopy A.31 Determining Lambda Max Using UV-Vis Spectrophotometer 1. Using a 1 mL volumetric pipette and a pipette bulb, we dispensed 1 mL of the stock copper sulfate solution into a volumetric flask and labeled it 1 mL copper. 2. Using a graduated cylinder we measured 5 mL of the 5M 𝑁𝐻4𝑂𝐻 and added it to the volumetric flask. 3. We filled the rest of the flask with distilled water till the 100 mL mark was reached, then we added the stopper and shook well. 4. We repeated steps 1 to 3 using a 5, 10, 25, 35 and 50 mL volumetric pipette to dispense the respective volume of stock copper sulfate solution into different volumetric flasks, and labeled the flasks accordingly. 5. We filled a 7th flask half way with distilled water and repeated steps 2 and 3. This flask was labeled Blank. 6. We filled one plastic cuvette 3/4th of the way with the blank solution and another one 3/4th of the way with the 25 mL copper solution prepared. 7. The blank cuvette was placed into the ‘reference cell’ compartment and the 25mL Copper into the ‘sample cell’ compartment in the UV-Vis spectrophotometer. We ran the machine and printed the spectrum obtained with the maximum wavelength reading annotated (Lambda max).
A.32 Calibration Curve of Spec 20 1. Making sure that the Spec 20 is properly heated, we took note of the instruments number and calibrate it by: a. Setting the proper range of the wavelength reading (the lambda max needs to fall within). b. Setting the wavelength to the maximum length measured in part 3.31. c. Making sure there is nothing in the sample holder, we adjusted the transmission reading to zero d. We placed a cuvette filled 3/4th of the way with the blank solution in the appropriate spot and adjusted the absorbance reading to zero. 2. We rinsed a cuvette and filled it 3/4th of the way with the first copper solution prepared. We then placed the cuvette in the sample holder and took note of the absorbance reading. We emptied the cuvette into the waste beaker and filled it again to repeat the reading 2 more times (without rinsing again as it is the same solution). 3. We repeat step 2 for the remaining five solutions of copper prepared.
A.33 Spec 20 Data for the Solution 1. Using a 5 mL volumetric pipette and a pipette bulb, we dispensed 5 mL of the Solution A into a 100 mL volumetric flask. 2. Using a graduated cylinder we measured 5 mL of the 5M 𝑁𝐻4𝑂𝐻 and added it to the volumetric flask. 3. We filled the rest of the flask with distilled water till the 100 mL mark was reached, then added the stopper and shook well. 4. We repeat steps 1 to 3 using volumetric pipettes to dispense two other volumes of solution A. Based on the color of the 5 mL solution, we determined that we should prepare a 10 mL and a 15 mL solution which we did and respectively labeled the flasks. 5. We rinsed a cuvette and filled it 3/4th of the way with the first dilution of the solution A prepared. We placed it in the sample holder of the spec 20 and took note of the
absorbance reading. We emptied the solution into the waste beaker and filled it again to repeat the reading 2 more times (without rinsing again as it is the same solution). 6. We repeated step 5 for the remaining two solutions of copper prepared. 7. We repeated steps 1 to 6 for the second solution A prepared for the other site.
A.4 Clean Up 1. We washed all the used glassware thoroughly with soap and water to ensure cleanliness. Then we dried and stored them in their appropriate spot. 2. We return all equipment borrowed to the Teaching Assistants. This includes the test tube cuvettes and their rack, the 25 ml volumetric pipette, the 250 ml volumetric flasks, by placing them in their designated storage areas after cleaning them. 3. We disposed of any chemical waste or used solutions in the designated waste disposal area according to the laboratory guidelines and safety protocols. 4. We wipe down the work area and address any spillage using appropriate cleaning materials. Ensuring that the work station is left clean and tidy. 5. We locked our lockers and returned any personal glassware belongings to their appropriate place or storage area. 6. We ensure that the fume hoods used are shut down and turned off the lights before leaving the laboratory.
Appendix C C.1.0 Extraction Data The resulting quantitative data for the extraction is in the table below: Table 5. Quantitative data of the copper extraction for the samples. Sample
Mass of Sample and Weighing Paper (g)
Mass of Empty Paper, (g)
Mass delivered, (g)
Uncertainty (g)
I3
5.225
0.225
5.000
± 0. 0005
G1
5.214
0.249
4.965
The only outstanding qualitative observation is the allotted time for the extraction of sample I3, taking a total of about 2 hours compared to 10 minutes for sample G1.
C.1.1 Extraction Calculations The calculations for the mass delivered are as shown, 𝑀𝑎𝑠𝑠 𝐷𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 = 𝑀𝑎𝑠𝑠 𝑜𝑓 𝑆𝑎𝑚𝑝𝑙𝑒 𝑎𝑛𝑑 𝑊𝑒𝑖𝑔ℎ𝑖𝑛𝑔 𝑃𝑎𝑝𝑒𝑟 − 𝑀𝑎𝑠𝑠 𝑜𝑓 𝐸𝑚𝑝𝑡𝑦 𝑃𝑎𝑝𝑒𝑟 𝑀𝑎𝑠𝑠 𝐷𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 = 5. 225 − 0. 225 = 5. 000 𝑔
C.2.0 Complexometric Titration Data The following tables contain the recorded data for the standardization of EDTA and complexometric titration of the sample. Table 6. EDTA complexometric titration raw data 0.15 M Stock Copper Sulfate Solution
Trial 1
Trial 2
Trial 3
Trial 4
Initial Volume (mL)
6.00
11.91
17.82
31.29
Final Volume (mL)
11.91
17.82
23.78
37.10
Volume Delivered (mL)
5.91
5.91
5.96
5.81
Average Volume Delivered (mL)
Table 7. Complexometric Titration data for sample I3
5.898
Sample G1
Trial 1
Trial 2
Trial 3
Initial Volume, (mL)
0.05
24.51
0.00
Final Volume, (mL)
24.51
49.62
25.12
Volume Delivered, (mL)
24.46
25.11
25.12
Average Volume Delivered (mL)
24.897
Table 8. Complexometric Titration data for sample G1 Sample I3
Trial 1
Trial 2
Trial 3
Initial Volume, (mL)
0.00
1.00
0.02
Final Volume, (mL)
27.12
28.14
27.14
Volume Delivered, (mL)
27.12
27.14
27.17
Average Volume Delivered (mL)
27.143
C.2.1 Standardization of EDTA Calculations For trial 1 of the standardization of EDTA, the volume of 0.15 M stock copper sulfate solution delivered was calculated to be 11. 91 − 6. 00 = 5. 91 𝑚𝐿 And the average, calculated with the equation 𝑉𝐴𝑣𝑒𝑟𝑎𝑔𝑒 =
𝑉1+𝑉2+𝑉3+𝑉4 𝑛𝑡𝑟𝑖𝑎𝑙𝑠
With 𝑉1, 𝑉2, 𝑉3, 𝑎𝑛𝑑 𝑉4 representing the volume delivered in trials 1-4. 𝑉𝐴𝑣𝑒𝑟𝑎𝑔𝑒 =
5.91+5.91+5.96+5.81 4
𝑉𝐴𝑣𝑒𝑟𝑎𝑔𝑒 = 5. 898 𝑚𝐿
Now using the average volume of the trials, the 0.05 M EDTA solution can be standardized, the unstandardized solution must be titrated against the stock copper (II) sulfate solution. Using the following equation the concentration of the EDTA solution is solved. 𝑐1𝑣1 = 𝑐2𝑣2 𝑐2 = 0. 05087 𝑀 EDTA Figure 9. The uncertainties associated with the standardization of the EDTA solution. Uncertainty
𝑒1 = 0. 132%
Source
𝑐1, uncertainty of the 𝑣1, uncertainty of the 10 𝑣2, uncertainty of the
𝑒2 = 0. 2%
stock copper solution
mL pipette
𝑒3 = 0. 2%
propagation for the final and initial volume in the burette
C.2.3 Sample Copper Sulfate Calculations Using the data from sample G1, multiplying the average volume of EDTA delivered and the concentration of EDTA the amount of moles deposited is calculated. Since the equivalence point is when the moles of both solutions are equivalent, the resulting value is the number of moles of CuSO4 𝑛 = 0. 05087 𝑀 × 0. 024897 𝐿 𝑛 = 0. 0012665 𝑚𝑜𝑙 Therefore, the volume, 0.024897 L results in the error of 𝑒4 = 0. 2% due to the burette again. Dividing the moles of CuSO4 by the total volume of the copper sulfate sample solution titrated, 0. 01𝐿 gives molarity of solution A with pipette uncertainty, 𝑒5 = 0. 2%. 𝑐=
0.0012665 𝑚𝑜𝑙 0.01 𝐿
𝑐 = 0. 12665 𝑀 𝐶𝑢𝑆𝑂4
It is known that the total volume of solution A is 100 mL, with uncertainty 𝑒6 = 0. 08%. Multiplying molarity and liters yields the total amount of Cu moles in the sample. There was a total of about 0.012665 mol or 0.80482 g of Cu in sample G1. Using the same process outlined above, there was a total of 0.013807 mol or 0.87742 g of Cu in sample I3.
The uncertainty of the final answer is derived through the equation. 𝑒=
2
2
2
2
2
2
𝑒1 + 𝑒2 + 𝑒3 + 𝑒4 + 𝑒5 + 𝑒6 = 0. 4289%
Therefore, the final compositions of the copper in each sample is 16. 21% ± 0. 43% for G1, internal, and 17. 55% ± 0. 43% for I3, external.
C.2.4 Complexometric Titration Uncertainty To calculate the uncertainty or error associated with the result, the uncertainties of all instruments used to take measurements need to be taken into account alongside their calculations.
C.3 Spectroscopy calculations
Figure 6. The spectrum of the graph obtained from the UV-Vis spectrophotometer for the solution containing 25 mL of the stock copper solution.
C.3.1 Spec 20 Calibration curve Table 10. Spec 20 Calibration Curve Raw Data Spec 20 id : 2
λ𝑚𝑎𝑥 = 600. 6𝑛𝑚
Volume of Copper Sulfate Stock (mL)
Absorbance Reading (Au) Trial 1
Trial 2
Trial 3
Trial 4 (optional)
1
0.094
0.086
0.086
0.082
5
0.370
0.369
0.370
10
0.700
0.710
0.704
25
1.150
1.150
1.150
35
1.220
1.218
1.217
50
1.248
1.250
1.250
0.704
Calculate the average absorbance for each volume of copper sulfate stock: 𝐴𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1.1+𝐴𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1.2+𝐴𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1.3+𝐴𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1.4
𝐴𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1 =
4
=
0.094+0.086+0.086+0.082 4
= 0. 087 𝐴𝑢
It is important to note that there is a dissociation reaction involved in this experiment for Copper (II) Ammonium sulfate Hexahydrate. The reaction is as follows: Cu(NH₄)₂SO₄·6H₂O (s) ⟶ 2NH₄⁺(aq) + Cu²⁺(aq) + SO₄²⁻(aq) + 6H₂O (l) Since there is a one to one ratio between the copper (II) ammonium sulfate hexahydrate and the copper itself, the molarity of Cu2+ can be determined by finding first the molarity of Cu(NH₄)₂SO₄·6H₂O. Calculate the concentration of each solution 𝐶𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1 =
𝐶𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝑢𝑙𝑓𝑎𝑡𝑒 𝑆𝑡𝑜𝑐𝑘×𝑉𝑎𝑑𝑑𝑒𝑑 1 𝑉𝑇𝑜𝑡𝑎𝑙
−3
=
0.1518×1×10 −3
100×10
−1
= 0. 001518𝑚𝑜𝑙. 𝐿
Then calculate the uncertainty of the concentration which is based on the uncertainty of the pipette used as the stock copper solution has no uncertainty.
∆𝐶𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1 =
(
=
(
∆𝑉𝑎𝑑𝑑𝑒𝑑 1 𝑉𝑎𝑑𝑑𝑒𝑑 1
2
) (
0.012 2 + 1
+
) (
∆𝐶𝐶𝑜𝑝𝑝𝑒𝑟 𝑠𝑡𝑜𝑐𝑘 𝐶𝐶𝑜𝑝𝑝𝑒𝑟 𝑠𝑡𝑜𝑐𝑘
)
2
× 𝐶𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 1
−1 0.0002 2 × 0. 001518 = 0. 0001𝑚𝑜𝑙. 𝐿 0.1518
)
Therefore the final concentration for the 1 mL solution is 0. 0015 ± 0. 0001𝑚𝑜𝑙. 𝐿
−1
as the
concentration is rounded to the last decimal place to be equal to the last decimal place of the uncertainty. However, for the 35 and 50 mL a combination of two pipettes was used to obtain that volume (25 mL and 10 mL, 25 mL two times respectively). Hence, the ∆𝑉𝑎𝑑𝑑𝑒𝑑 1 is the square root of each of the absolute uncertainties of the pipettes squared. For example for the 35 mL solution, it would be: ∆𝑉𝑎𝑑𝑑𝑒𝑑 1 =
2
2
∆𝑉𝑃𝑖𝑝𝑒𝑡𝑡𝑒 25 + ∆𝑉𝑃𝑖𝑝𝑒𝑡𝑡𝑒 10 =
2
2
0. 06 + 0. 02 = 0. 063𝑚𝐿
Table 11. Spec 20 Calibration Curve Final Data Volume of Copper Sulfate Stock (mL)
Average Absorbance Reading (Au)
Concentration of
(
Copper 𝑚𝑜𝑙. 𝐿
−1
)
Uncertainty of the Concentration of the
(
Copper 𝑚𝑜𝑙. 𝐿
1
0.087
0.0015
0.0001
5
0.370
0.0075
0.0007
10
0.705
0.0152
0.0014
25
1.150
0.0380
0.0035
35
1.218
0.0531
0.0050
50
1.249
0.0759
0.0071
−1
)
2
When plotting the calibration curve (Figure 7) the 𝑅 value for the straight line was low, around 0.82. This is because there is a curvature associated with the points that is prevalent especially after the first three concentrations. This makes the points unreliable. Hence, for a more accurate calibration curve, it was plotted using only the first three points (Figure 8).
Figure 7. Calibration curve with all the concentration points.
Figure 8. Calibration curve including only the first three concentration points. Using the calibration curve in figure 8, it will be possible to determine the weight percentage of copper in each site.
C.3.2 Internal Site Weight Percent Calculations from Spectroscopy Data Table 12. Site 1 (G1, Internal) Spec 20 (#2) Raw Data Spec 20 id : 2
λ𝑚𝑎𝑥 = 600. 6𝑛𝑚
Volume of Site 1 Stock (mL)
Absorbance Reading (Au) Trial 1
Trial 2
Trial 3
Trial 4 (optional)
5
0.349
0.343
0.342
0.348
10
0.616
0.614
0.616
15
0.845
0.843
0.845
Calculate the average absorbance for each volume of site 1 stock:
𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5 =
𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5.1+𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5.2+𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5.3+𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5.4 4
=
0.349+0.343+0.342+0.348 4
= 0. 346 𝐴𝑢
From the formula in the calibration curve it is known that: 𝐴 = 0. 309 × 𝐶𝐶𝑜𝑝𝑝𝑒𝑟 + 0. 0783 𝐴−0.0783 0.309
Hence, 𝐶𝐶𝑜𝑝𝑝𝑒𝑟 =
The average absorbance for each solution is plugged into the equation and the concentration of −1
copper in that solution is obtained in 𝑚𝑜𝑙. 𝐿 . For example for the 5 mL solution: 𝐶𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5 =
𝐴𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5−0.0783 0.309
0.346−0.0783 0.309
=
= 0. 8647
From the concentration it is possible to now calculate the weight percentage using the following: 𝑤𝑡%𝐶𝑢 =
𝐶𝐶𝑜𝑝𝑝𝑒𝑟×𝑀𝑤 𝐶𝑢×𝑉𝑎𝑑𝑑𝑒𝑑 𝑚𝑠𝑎𝑚𝑝𝑙𝑒
× 100
For the 5 mL solution the equation would be: 𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5 =
𝐶𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5×𝑀𝑤 𝐶𝑢×𝑉𝑎𝑑𝑑𝑒𝑑 5 𝑚𝑠𝑎𝑚𝑝𝑙𝑒 𝑆𝑖𝑡𝑒𝑂𝑛𝑒
× 100 =
0.08647×63.546×5 4.965
× 100 = 2. 213%
The uncertainty of this weight percentage can be calculated taking into account the uncertainty of the balance used in order to weight the sample and the uncertainty of the pipette used while assuming that the calibration curve is correct using the following formula:
∆𝑤𝑡%𝐶𝑢 =
(
∆𝑉𝑎𝑑𝑑𝑒𝑑 𝑉𝑎𝑑𝑑𝑒𝑑
2
) ( +
∆𝑚𝑠𝑎𝑚𝑝𝑙𝑒 𝑚𝑠𝑎𝑚𝑝𝑙𝑒
2
)
× 𝑤𝑡%𝐶𝑢
For the 5 mL sample it will be:
∆𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5 =
=
(
∆𝑉𝑎𝑑𝑑𝑒𝑑 5 𝑉𝑎𝑑𝑑𝑒𝑑 5 0.02 2 5
2
) (
( ) +(
+
∆𝑚𝑠𝑎𝑚𝑝𝑙𝑒 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 𝑚𝑠𝑎𝑚𝑝𝑙𝑒 𝑆𝑖𝑡𝑒𝑂𝑛𝑒
)
2
× 𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5
0.001 2 × 2. 213 = 0. 009% 4.965
)
Thus, ending up with the following data presented in table 13 for the three solutions prepared from the internal site standard solution prepared.
Table 13. Spec 20 Site 1 Final Data Volume of Copper Sulfate Stock (mL)
Average Absorbance Reading (Au)
Concentration from calibration curve (mol/L)
Copper weight percent (wt%)
Concentration Uncertainty (wt%)
5
0.346
0.8647
2.213
0.009
10
0.615
1.7380
2.224
0.082
15
0.844
2.4791
2.115
0.111
The average weight percent is: 𝐶𝑜𝑝𝑝𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝐼𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑆𝑖𝑡𝑒 = =
𝐶𝑜𝑝𝑝𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑝𝑒𝑟𝑐𝑒𝑛𝑡5+𝐶𝑜𝑝𝑝𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑝𝑒𝑟𝑐𝑒𝑛𝑡10+𝐶𝑜𝑝𝑝𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑝𝑒𝑟𝑐𝑒𝑛𝑡15 3 2.213+2.224+2.115 3
= 2. 184%
The uncertainty of it will be based on the uncertainties of each of the individual solutions summed in the following manner: ∆𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 = =
2
2
2
2
∆𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 5 + ∆𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 10 + ∆𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 15 × 𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 2
2
0. 009 + 0. 082 + 0. 111 = 0. 302%
Therefore, the weight percent of copper for the internal site based on spectroscopy is 2. 2 ± 0. 3% Based on the given data for this site, the true weight percent is 16.62% The error can be therefore calculated: %𝑒𝑟𝑟𝑜𝑟 =
𝑤𝑡%𝐶𝑢 𝐺1 𝑇𝑟𝑢𝑒−𝑤𝑡%𝐶𝑢 𝑆𝑖𝑡𝑒𝑂𝑛𝑒 𝑤𝑡%𝐶𝑢 𝐺1 𝑇𝑟𝑢𝑒
× 100 =
16.62−2.2 16.62
= 87%
Hence the value obtained by spectroscopy is 87% wrong.
C.3.3 External Site Weight Percent Calculations from Spectroscopy Data Table 14. Site 2 (I3, External) Spec 20 (#2) Raw Data Volume of Site 2 Stock (mL)
Absorbance Reading (Au) Trial 1
Trial 2
Trial 3
5
0.310
0.311
0.309
10
0.586
0.586
0.588
15
0.798
0.792
0.796
Trial 4 (optional)
0.794
The same calculation procedure implementation for internal site, is done for external site data (Table 14) and ending up with the following. Table 15. Spec 20 Site 2 Final Data Volume of Copper Sulfate Stock (mL)
Average Absorbance Reading (Au)
Concentration of Copper
Uncertainty (wt%)
Concentration Uncertainty (wt%)
5
0.310
0.7498
1.906
0.008
10
0.587
1.6452
2.091
0.078
15
0.795
2.3194
1.965
0.104
(𝑚𝑜𝑙. 𝐿−1)
The weight percent of copper for the internal site based on spectroscopy is 2. 0 ± 0. 3% Based on the given data for this site, the true weight percent is 18.34%, and the error of the value obtained by spectrophotometry is 89% wrong.