Chem152_AES_Report_080110

Chem152_AES_Report_080110 - Name: ID Number: Quiz Section:...

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Unformatted text preview: Name: ID Number: Quiz Section: Lab Partner: Points assigned to tables, graphs questions, and calculations. EXPERIMENT 6: ATOMIC EMISSION SPECTROSCOPY(AES) Part I. Measuring the Hydrogen Emission Spectrum Part II. An Application of AES; Determination of Sodium Note: All sections of this report must be typed Total Points = 60 (5 notebook, 55 template) By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will cost you 5 points. Signature: Part I. Measuring the Hydrogen Emission Spectrum Use these in the data analysis. Data here will autofill into the third column of Tables 2-4 DATA Table 1. Hydrogen Emission Data Spectroscope Data Color violet blue-green red Ocean Optics Spectrometer λ (nm) (descending order) Wavelength, nm A: Data Analysis Hypothesis #1: nf (assumed) = 1; therefore ni = 2, 3, 4, 5, 6. If the hypothesis is correct, a plot of 1/λ vs. 1/ni2 should be linear (good R2 ) and the Rydberg constants calculated from slope and the y-intercepts should be the same. Calculate 1/λ and 1/ni2 , then plot the data and include the equation and R2 on the plot. Compare the R values calculated from the slope and y-int. Table 2. Hypothesis #1; nf = 1; ni = 2, 3, 4, 5, 6 ni values 1/ni2 λ (nm) 0.0 0.0 0.0 0.0 0.0 1/λ nm-1 Put your plot of 1/λ vs 1/ni2 here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. Excel Help for Data in Tables 2, 3 &4 1. Column B: =1/(Click on column A entry)^2, Enter. Copy and paste into remaining cells. 2. Column D: =1/(Click on Column C entry), Enter. Copy and paste into other cells. 3. Format cells to desired number of decimal places. Highlight cells, Format, Number, select number of decimal places. A number that does not fit the column width will show an error and a number that is too small for the formatting will register as zero. You also have the option to write the number in scientific notation. 4.Plot 1/λ on the y-axis and 1/ni2 on the x-axis. Right click on any data point and add a trendline. In the trendline help box, choose linear type, and under the options tab, click on the boxes in front of "display equation on chart" and "display Rsquared on chart". Right click on the equation, choose "format data labels" or "format trendline label" and change the number properties so that 5 sig figs are displayed. (Failure to do this on each plot will cost you a point!) 5. From the Rydberg equation, you know that the slope is equal to -R and the y-intercept is equal to R/nf2. Calculate R both ways and compare. Report your results to 4 or 5 sig figs. Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will "display the equation on the chart". Slope: y-intercept: R from slope: R from y-intercept: nm-1 nm-1 Is nf=1? Hypothesis #2: nf (assumed) = 2; therefore ni = 3, 4, 5, 6, 7. If the hypothesis is correct, a plot of 1/λ vs. 1/ni2 should be linear (good R2 ) and the Rydberg constants calculated from slope and the y-intercepts should be the same. Calculate 1/λ and 1/ni2 , then plot the data and include the equation and R2 on the plot. Compare the R values calculated from the slope and y-int. Page 1 of 12 Hypothesis #2: nf (assumed) = 2; therefore ni = 3, 4, 5, 6, 7. If the hypothesis is correct, a plot of 1/λ vs. 1/ni2 should be linear (good R2 ) and the Rydberg constants calculated from slope and the y-intercepts should be the same. Calculate 1/λ and 1/ni2 , then plot the data and include the equation and R2 on the plot. Compare the R values calculated from the slope and y-int. Table 3. Hypothesis #2; nf = 2; ni = 3, 4, 5, 6, 7 ni values 1/ni2 λ (nm) 0.0 0.0 0.0 0.0 0.0 1/λ nm-1 Put your plot of 1/λ vs 1/ni2 here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will "display the equation on the chart". Slope: y-intercept: R from slope: R from y-intercept: nm-1 nm-1 Is nf=2? Hypothesis #3: nf (assumed) = 3; therefore ni = 4, 5, 6, 7, 8. If the hypothesis is correct, a plot of 1/λ vs. 1/ni2 should be linear (good R2 ) and the Rydberg constants calculated from slope and the y-intercepts should be the same. Calculate 1/λ and 1/ni2 , then plot the data and include the equation and R2 on the plot. Compare the R values calculated from the slope and y-int. Table 4. Hypothesis #3; nf = 3; ni = 4, 5, 6, 7, 8 ni values 1/ni2 λ (nm) 0.0 0.0 0.0 0.0 0.0 1/λ nm-1 Put your plot of 1/λ vs 1/ni2 here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will "display the equation on the chart". Slope: y-intercept: R from slope: R from y-intercept: nm-1 nm-1 Is nf=3? Summary of information to be used in the next section (from the data for the correct nf value above): R (in SI units) b (in SI units) m-1 m-1 B: Ionization Energy and Energy Levels Enter the values for h and c, then calculate the ionization energy per atom from nf (IE = hc·b),where b is the y-intercept in m-1. Page 2 of 12 h (Planck's const) c (speed of light) Js Type the calculation of IE per atom from nf IE(per atom) m/s J If nf is not 1, the IE calculated above is not the regular ionization energy. We need to add an energy term, for the ground state (n =1) to nf transition, to the IE just calculated. This energy term is equal to 3/4hcR for nf=2 and 8/9 hcR for nf=3. Calculate IEtotal from ground state (nf = 1), both per atom and per mole: Type the calculation of IEtotal per atom and per mole. IE(per atom) J Avogadro's # mole -1 IE (per mole) J/mole Calculate the allowed energy levels: En(per atom) = -hcR/n2 where n= 1, 2, 3, ... (with R in units of m-1) The cells under the h, c, and R headings below will autofill from cells B140, C140, and B133, respectively, so you just need to enter the formula in Column F to calculate En. En n h c R Eα ∞ 0.000E+00 0.000E+00 E4 4 0.000E+00 0.000E+00 0.000E+00 E3 3 0.000E+00 0.000E+00 0.000E+00 E2 2 0.000E+00 0.000E+00 0.000E+00 E1 1 0.000E+00 0.000E+00 En(J) 0.000E+00 0.000E+00 Part II. An Application of AES; Determination of Sodium DATA Molar mass of NaCl Calculated mass of NaCl needed to make 100 mL of 0.100 M stock solution Actual mass of NaCl weighed out Actual molarity of stock NaCl solution prepared g/mole g g M Volume of 0.100 M stock NaCl solution for preparing 100 mL of each standard Desired mL of 0. 1M NaCl Standard Final [NaCl] (M) needed Note: 1 0.0010 For Table 5, calculate the ACTUAL [Na+] (M and mg/8 fl. oz.) of the 2 0 standards based on the mass of NaCl you weighed out. Use the 3 0 conversion factor: 4 0 5 0 8 fl oz. = 0.2366 L to calculate the [Na+] in mg/8 fl.oz. Table 5: Flame Photometer Data Sample [Na+], (M) Standard 1 Standard 2 Standard 3 Standard 4 Standard 5 Table 5 (continued) Sample Gatorade Coca Cola Site #1, 8.5 m depth Site #1, 9.5 m depth Site #1, 10.5 m depth Site #1, 11.5 m depth Seawater [Na+], (mg/8 fl oz) Intensity Dilution Factor 25 2.5 1 2 10 100 400 Intensity For your convenience, the depth, dilution factors, and intensity values for the freshwater and seawater samples will autofill in the tables below. DATA ANALYSIS Put your plot of Intensity vs. [Na+] (M) here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Page 3 of 12 Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. You will plot the data and obtain the trendline equation from the graph. This will be the calibration equation in the form of y=mx+b and you will use it, with your intensities (y) from the data table above, to determine the [Na+] in the samples. For the drink samples, you will need to convert the [Na+] from M to mg/8 fl oz. in order to compare with the manufacturers' values. Put your plot of Intensity vs. [Na+] (M) here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will "display the equation on the chart". You will plot the data and obtain the trendline equation from the graph. This will be the calibration equation in the form of y=mx+b and you will use it, with your intensities (y) from the data table above, to determine the [Na+] in the samples. For the drink samples, you will need to convert the [Na+] from M to mg/8 fl oz. in order to compare with the manufacturers' values. slope y-intercept M-1 Using the calibration equation (eqn of the line), calculate the concentration of sodium in the original samples. What percent of the labeled value is the measured value? mg/8 fl. oz, sports drink mg/8 fl.oz on label % measured vs labeled values mg/8 fl. oz. for the cola drink mg/8 fl.oz on label % measured vs labeled values Helpful Hints: Calculating concentrations from measured atomic emission intensities 1. y = mx + b, where y = your measured intensity and m and b are the slope and intercept from your plot, respectively. 2. Solve for 'x', multiply by the appropriate dilution factor from Table 5, and, for the cola and gatorade samples, convert the answer from M to mg/8 fl oz. 3. Also for the cola and gatorade samples, find the ratio of the measured amount to the reported amount. In other words, the measured amount is what % of the maximum amount allowed in the sample as reported on the label? Type the calculation for determining the concentration of Na+ in the original Gatorade sample in units of mg/8 fl.oz. Freshwater samples as a function of depth: Depth (m) Intensity Dilution Factor 8.5 0 1 9.5 0 2 10.5 0 10 11.5 0 100 Concentration (M) Page 4 of 12 Put your plot of concentration (M) vs depth here. Make your plot big enough to cover this instruction box so that it is large enought for someone else to read. Use the online resources if you need help figuring out how to plot a graph in Excel. Choose an XY scatter plot with a smooth line and data markers. Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you print the report. At the deepest point, what is the ratio of Seawater to Freshwater? What about the most shallow point? Seawater Dilution Factor 400 Intensity Concentration (M) 0 Dilution Factor = [Na Seawater]/[Na Freshwater, deepest point or most shallow point] deepest most shallow Type the calculation for determining the concentration of Na+ in the original seawater sample. RESULTS AND DISCUSSION 1. Which of the three hypotheses fits the Rydberg equation? Explain your choice. 2. Based on your data, which ni and nf values are associated with the most intense peak near 650 nm? 3. How well does your ionization energy compare with the literature value of 1.312 x 106 J/mole? Calculate and discuss the % error. 4. The flame photometer uses a natural gas flame (~ 1800 oC). What would happen to the emission intensities if an acetylene - nitrous oxide flame (~3000 oC) was used instead? Page 5 of 12 5. Assuming your measured Na concentrations are correct, how accurate is the labelling on the drinks? Calculate and discuss the % error. 3. How well does your ionization energy compare with the literature value of 1.312 x 106 J/mole? Calculate and discuss the % error. 4. The flame photometer uses a natural gas flame (~ 1800 oC). What would happen to the emission intensities if an acetylene - nitrous oxide flame (~3000 oC) was used instead? 5. Assuming your measured Na concentrations are correct, how accurate is the labelling on the drinks? Calculate and discuss the % error. Laboratory Waste Evaluation (1 pt) Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer drain, thrown in the garbage, collected in a container for disposal by the UW Environmental Health & Safety department, or released into the environment. Based on the written lab procedure and your actions during the lab, list the identity and approximate amount (mass or volume) of waste that you generated while performing this experiment. Page 6 of 12 ned to tables, graphs ns, and calculations. 5 a in Tables 2, 3 lick on column A y and paste into lick on Column C and paste into esired number Highlight cells, lect number of umber that does idth will show an that is too small ill register as the option to scientific axis and 1/ni2 on ick on any data dline. In the choose linear options tab, n front of "display nd "display RRight click on the ormat data endline label" ber properties displayed. on each plot nt!) 1 g equation, you is equal to -R is equal to R/nf2. ys and our results to 4 2 3 Page 7 of 12 1 2 3 1 2 3 1 Page 8 of 12 from nf 2 r mole. 2 2 2 1 1 onvenience, the tion factors, and lues for the and seawater ill autofill in the w. ain the trendline s will be the m of y=mx+b and sities (y) from the e the [Na+] in the les, you will need mg/8 fl oz. in nufacturers' Page 9 of 12 ain the trendline s will be the m of y=mx+b and sities (y) from the e the [Na+] in the les, you will need mg/8 fl oz. in nufacturers' 2 mic emission the slope and e 5, and, for the oz. sured amount to t % of the 2 3 1 Page 10 of 12 2 2 3 2 2 2 Page 11 of 12 2 2 1 60 Page 12 of 12 ...
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