Purpose: Prepare for the lab by answering the following questions. Use complete sentences, avoiding the use of "I" or "we". 1. What is the main topic/concept being investigated today? Phosphate levels

in water 2. How will you investigate this topic/concept? Determining the phosphate levers in al waters and including 2 of our own samples 3. Write the main definitions and equations needed for today's experiment. Phosphate, M1V1=M2V2, ppm, absorbance, cure, treated, y=mx+b/nData: 1) Give brief names to your two water samples: a. Sample 1: b. Sample 2: 2) Table 1 shows the concentration of the solutions you need to prepare. First, calculate the volume of stock solution you need to prepare each of these in units of mL. Then convert these measurements to uL. Show your work below the table. Concentration of Phosphate in Stock Solution 20. ppm 20. ppm 20. ppm 20. ppm 20. ppm Table 1: Volumes of stock solution used to make standards Volume of Stock Solution to Pipette In mL In μL 50 .05 .1 2 FL 4 .8 Y17 100 200 400 800 Concentration of Phosphate in Diluted Solution 0.02 ppm 0.04 ppm 0.08 ppm 0.16 ppm 0.32 ppm Final Volume of Diluted Solution 50.0 mL 50.0 mL 50.0 mL 50.0 mL 50.0 mL/n3) Record the absorbance measurements for your samples below: Table 2: Absorbance Values of Standards and Unknowns. Sample Phosphate Concentration (in ppm) 0 ppm 0.02 ppm 0.04 ppm 0.08 ppm 0.16 ppm 0.32 ppm .5339ppm 5460 ppm Blank Standard Solution 1 Standard Solution 2 Standard Solution 3 Standard Solution 4 Standard Solution 5 FL Y17 Absorbance at 2.-690 nm 0.001 0.325 0.292 0.413 0.315 0.039 0.054 0.049/nCalculations: 1) Construct a phosphate standard curve in Excel by plotting concentration (in ppm) on your x-axis and Absorbance (unitless) on your y-axis for your known solutions. Label the axes on the graph and provide the curve with a title. Use a linear trendline to generate a best fit line to your data. Label the graph with the equation and the R² value. Insert your labeled graph in the space below. https://ggcedu-my.sharepoint.com/x:/g/personal/malvarez6 BZ_V-pQhDkQ8pSQXmmgNWYQ?e-toARa7 ggc_edu/EXA4XwkKmThKqxSAmvcZUnl canvas | 12 BA 2) Using the equation from your graph, determine the phosphate concentration (in ppm) in each of your natural water samples. y=mx+b 054-0.4141x+0.2751 x 5339ppm 0.049 -0.4141x+0.2751 x 5460ppm 3) Record your answers from (2) in Table 2 above. Analysis and Discussion 1) Since this is a multi-week experiment, we do not need to write a conclusion yet. However, it is helpful to summarize the results from each week. Summarize your results for this week. Briefly state the experiment performed, and the results found. Use complete sentences and avoid the use of "I" or "we". added ammonium solution then the tint to all tubes, added 50 ml of distilled water to all except two of them because there needed to be added 50ml of both samples FL and y17 then let them sit for 10 min forgot to add the phosphate so then added it and waited again then checked the absorbance with the spectroscopy and wrote down data 2) Error Analysis: How accurate is your straight line? a. Examine your graph. Do most of your points fall on the best fit line, or are there outliers?/nDefinitely not accurate we made a couple mistakes, we forgot to add phosphate until the end, and had some spillage, may have probably mixed up the tubes since they had other labels on them from other groups b. The R² value is a measure of how close your experimental values match the corresponding values from the straight line. If R² > 0.95, this indicates the straight line is a good approximation of your data. If R² < 0.95, then then the line is not a good approximation of your data. Discuss how good your fit is based on the R² value. Not so good our data isnt accurate or precise so its kinda scrambled c. Outliers and a poor R² value are usually due to poor experimental technique. Based on your graph, rate your experimental technique on a scale from 1-10. Explain your reasoning. It was okay until we forgot the phosphate and spilled some of out liquids but we stayed as professional as we could and waited more time after adding it since we forgot about it 3) Answer the following questions regarding the phosphate concentrations in your water sources. a. Is the measured concentration of phosphate what you expected for the water sources you tested? Why or why not? No i expected there to be a whole lot more in the y17 late since according to xavier a lot of people go there b. What are the point and nonpoint pollution sources that could contribute to higher than expected phosphate level? What might contribute to a lower than expected level? Sewers, people dumping trash c. Is the water potable? mehhh needs some treatment but it should be fine yes d. Would the water be useful for uses other than drinking? yes/ne. Would the water need to be treated before using it? yes f. What recommendations would you make to a user of this water source? make sure you keep it clean and try not to drink from it