Chem AES Postlab 05.31.10

Chem AES Postlab 05.31.10 - Atomic Emission Spectroscopy...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Atomic Emission Spectroscopy (AES) Name: ID Number: Emily Tsiao 930609 Quiz Section: AD Lab Partner: Haley Smith 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 Total Points = 60 (5 notebook, 55 template) Note: All sections of this report must be typed 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: Emily Tsiao 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. Part I. Measuring the Hydrogen Emission Spectrum DATA Table 1. Hydrogen Emission Data Spectroscope Data Color violet blue-green red Wavelength, nm 420 480 660 Use these in the data analysis. Data here will autofill into the third column of Tables 2-4 Ocean Optics Spectrometer λ (nm) (descending order) 657.6 486.6 435.2 410.9 396.5 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 2 3 4 5 6 1/ni2 0.25000000 0.11111111 0.06250000 0.04000000 0.02777778 λ (nm) 657.6 486.6 435.2 410.9 396.5 1/λ nm-1 0.00152073 0.00205524 0.00229806 0.00243386 0.00252232 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. 1/λ nm-1 vs 1/ni2 1/λ nm-1 vs 1/ni2 Use the online resources if you need help figuring out how to plot a graph in Excel. 0.30000000 0.00300000 Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and 0.00250000 0.25000000 f(x) = -224.54x + 0.58 formatting once you print the= 0x + 0 f(x) report. 0.002000000.99 R² = R² = 0.99 0.20000000 Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will 0.00150000 "display the equation on the chart". Column 1/ni2 D 0.15000000 0.00100000 Linear Regression for Linear Regression for 0.10000000 0.00050000 Column D 1/ni2 0.00000000 0.05000000 0.00000000 0.05000000 0.00000000 0.00140000 0.00160000 1/λ nm-1 0.10000000 0.15000000 0.20000000 0.25000000 0.00240000 0.30000000 0.00260000 0.00180000 0.00200000 1/ni2 0.00220000 Slope: y-intercept: 0 0 R from slope: R from y-intercept: 0 nm-1 0 nm-1 Is nf=1? No 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. Atomic Emission Spectroscopy (AES) 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 3 4 5 6 7 1/ni2 0.11111111 0.06250000 0.04000000 0.02777778 0.02040816 λ (nm) 657.6 486.6 435.2 410.9 396.5 1/λ nm-1 0.00152073 0.00205524 0.00229806 0.00243386 0.00252232 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 0.00300000 someone else to read. 1/1/λnm-1 vs 1/ni2 λ nm-1 vs 0.00250000 f(x) = -0.01x + 0 Use the online resources if you need help figuring out how to plot a graph in Excel. 0.12000000 Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting 0.10000000 0.00200000 0.00300000 once you print the report. 1 R² = 0.08000000 f(x) = -0.01x + 0 0.00150000 0.00200000 Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that will "display the R² = 1 0.06000000 1/ni2 equation on the chart". 0.00100000 0.00100000 0.04000000 R²f(x)1 -90.94x + 0.25 == 1/λ nm-i1 1/n 2 Column D 0.00050000 0.00000000 0.02000000 0.00000000 0.00000000 0.00000000 0.00140000 0.02000000 0.02000000 0.00160000 0.04000000 0.04000000 0.00180000 0.06000000 0.06000000 0.00200000 0.08000000 0.08000000 0.00220000 Linear Regression for Column Linear Regression for 1/ni2 Column D D Linear Regression for Column D 0.10000000 0.12000000 0.12000000 0.00260000 1/ni2 0.10000000 0.00240000 Slope: y-intercept: -0.01 0 R from slope: R from y-intercept: 0.01 nm-1 0.01 nm-1 Is nf=2? Yes 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 4 5 6 7 8 1/ni2 0.06250000 0.04000000 0.02777778 0.02040816 0.01562500 λ (nm) 657.6 486.6 435.2 410.9 396.5 1/λ nm-1 0.00152073 0.00205524 0.00229806 0.00243386 0.00252232 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. 1/λ /λ nm-1nm-1 1 nm-1λ vs 1/ni2 1/ vs 1/ni2 vs 1/ni2 0.07000000 Use the online resources if you need help figuring out how to plot a graph in Excel. 0.06000000 f(x) = -46.63x + 0.13 Title the graph and label the X and Y axis, including the correct units. Be sure to double check your units and formatting 0.00400000 0.08000000 R² = 1 once you print the report. 0.05000000 0.06000000 f(x) = -46.63x + 0.13 0.00200000 f(x) = -0.02x + 0 0.04000000 Add a Trendline to show the linear fit 1 your data. Choose a linear line and choose the options that will "display the 1/ni2 of 0.04000000 R² = 1 R² = Column B Column D 0.03000000 equation on the chart". 0.00000000 Linear Regression for 1/ni2 0.01000000 0.02000000 0.03000000 0.04000000 0.05000000 0.06000000 0.07000000 Linear Regression for Column 0.02000000 0.02000000 B D 0.01000000 0.00000000 Column B 0.00140000 0.00160000 0.00180000 0.00200000 0.00220000 0.00240000 0.00260000 0.00000000 1/λ nm -1 /ni2 1 0.00140000 0.00160000 0.00180000 0.00200000 0.00220000 0.00240000 0.00260000 i 1/1/λ m-1 -1 λ n nm 1/n 2 1/ni2 Slope: y-intercept: -0.02 0 R from slope: R from y-intercept: 0.02 nm-1 0.03 nm-1 Is nf=3? No 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) 1.100E+07 m-1 2.700E+06 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 Atomic Emission Spectroscopy (AES) h (Planck's const) 6.62600E-34 c (speed of light) 3.000000E+08 IE(per atom) 5.3700E-19 Type the calculation of IE per atom from nf Js m/s J I E=hc* b (b fr om nf 2)=5.36e-19s 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: IE(per atom) Avogadro's # IE (per mole) 1.640E-18 J 6.02200E+23 mole -1 Type the calculation of IEtotal per atom and per mole. I E t ot al =hcb + 3/4hcR= 1.64e-18 (hcb(nf2) + 3/4hcR= (1.64e-18)* 6.022e23=j/mol 9.8728E+05 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 E4 E3 E2 E1 ∞ 4 3 2 1 6.626E-34 6.626E-34 6.626E-34 6.626E-34 6.626E-34 3.000E+08 3.000E+08 3.000E+08 3.000E+08 3.000E+08 1.100E+07 1.100E+07 1.100E+07 1.100E+07 1.100E+07 En(J) 0 0 0 0 0 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 58.44 g/mole 0.58 g 0.5040 g 0.8620 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 1.00 For Table 5, calculate the ACTUAL [Na+] (M) of the standards 2 0 0.80 based on the mass of NaCl you weighed out. Use the conversion 3 0 0.60 factor: 4 0 0.40 5 0 0.20 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 0.00100 Standard 2 0.00080 Standard 3 0.00060 Standard 4 0.00040 Standard 5 0.00020 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) 6.00 4.80 3.60 2.40 1.20 Dilution Factor 25 2.5 1 2 10 100 400 Intensity 100 90 76 64 56 Intensity 82 37 66 65 76 44 95 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. Intensity Concentration Intensity vs vs [Na+] (M) Use the120 online resources if you need help figuring out how to plot a graph in Excel. 0.00120 f(x) = label Title the graph and 0x - 0the X and Y axis, including the correct units. BePage to of 12 check your sure 3 double 100 0.00100 units and formatting57000x + 43 the report. R² = = once you print f(x) 0.99 nsity 80 R² = 0.99 0.00080 Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that 60 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. Atomic Emission Spectroscopy (AES) 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. Intensity Concentration Intensity vs vs [Na+] (M) Use the120 online resources if you need help figuring out how to plot a graph in Excel. 0.00120 80 R² = 0.99 0.00080 Add a Trendline to show the linear fit of your data. Choose a linear line and choose the options that 60 will "display the equation on the chart". Column E [Na+], (M) 0.00060 40 Linear _____ Regression 0.00040 for Column E [Na+], (M) 20 0.00020 0 0.00010 0.00020 0.00030 0.00040 0.00050 0.00060 0.00070 0.00080 0.00090 0.00100 0.00110 0.00000 50 60 70 Concentration 80 90 100 110 I ntensity [Na+] Intensity(M ) f(x) = label Title the graph and 0x - 0the X and Y axis, including the correct units. Be sure to double check your 100 0.00100 units and formatting57000x + 43 the report. R² = = once you print f(x) 0.99 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 5.70E+04 M-1 43.00 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? 93 110 85 mg/8 fl. oz, sports 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? 1.432 35 0.04 mg/8 fl. oz. for the cola drink mg/8 fl.oz on label % measured vs labeled values Type the calculation for determining the concentration of Na+ in the original Gatorade sample in units of mg/8 fl.oz. y=mx +b int ensit y= 57000x +43 , 82= 57000x + 43 x= 6.84E-4 (6.84e-4M )(0.2366L /8f loz)(23g(Na)/mol(Na))(1000mg/g)=3.72(25)=93.08 Freshwater samples as a function of depth: Depth (m) Intensity Dilution Factor Concentration (M) 8.5 66 1 0.00040 9.5 65 2 0.00077 10.5 76 10 0.00579 11.5 44 100 0.00175 Page 4 of 12 Atomic Emission Spectroscopy (AES) 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. Concentration vs Depth 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 0.00700 and data markers. 0.00600 Title the 0.00500 label the X and Y axis, including the correct units. Be sure to double check your units and formatting once you graph and print the report. 0.00400 0.00300 f(x) = 0x - 0 0.00200 R² = 0.22 0.00100 0.00000 40 45 50 55 60 Depth (m) 65 70 75 80 Column D Linear Regression for Column D Concentration (M) At the deepest point, what is the ratio of Seawater to Freshwater? What about the most shallow point? Seawater Dilution Factor 400 Intensity 95 Concentration (M) 0.36491 Dilution Factor = [Na Seawater]/[Na Freshwater, deepest point or most shallow point] deepest 0.03173 most shallow 3.1017 Type the calculation for determining the concentration of Na+ in the original seawater sample. y=mx + b int ensit y=[Na]x + yint er cept 95=57000x + 43 [(95-43)/ slope] X dilut ion fact or = 0.36491 RESULTS AND DISCUSSION 1. Which of the three hypotheses fits the Rydberg equation? Explain your choice. T he hypot hesi s t hat best fit s t he Rydberg equat i on is nf=2. Nf=2 pr oduced t he same R when solvi ng for R by using t he slope and y-i nt er cept t hat s how I knew t hat nf=2 was t he cor r ect hypot hesis 2. Which ni and nf values are associated with the most intense peak near 650 nm? T he ni and nf val ues that ar e associ ated wi th the most i ntense peak ar e ni =3 and nf=3 I can see thi s by l ooki ng at the cor r ect hypothesi s gr aph when nf=2 3. How well does your ionization energy compare with the literature value of 1.312 x 106 J/mole? Calculate and discuss the % error. T he value t hat I calculat ed for I E was 9.873e5 J/moles % er r or = (my value-act ual)/act ual X 100= 24.75% er r or The per cent er r or could have come fr om not measur ing t he wavelengt h at t he middle of i t s peak. Thi s would cause our gr aphs t o be off which would change our R causing t he I E value t o be slight ly differ ent . 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? I f t he t emperat ur e was incr eased t hat means t hat we ar e also incr easing t he amount of ener gy and when we have mor e energy t he int ensit y will be higher. So t her efor e t he emission int ensit ies woul d be higher if acet ylene-nit r ous oxide was used. 5. Assuming your measured Na concentrations are correct, how accurate is the labelling on the drinks? Calculate and discuss the % error. T he labeling on t he dr inks is more accur at e for t he gat or ade t han it is for t he coke. When I calculat ed t he amount of sodium in t he gat or ade I got 93mg vs t he 110mg t hat was on t he label. The gat or f 12 label was r elat ively accur at e wit h 15.45% er r or, while Page 5 o ade t he coca-cola had an 99.6% er r or. For t he coca cola t he label sai d 35mg and when we did t he exper iment we only found 1.43mg. % er r or = (my val ue-act ual)/act ual X 100= 15.45 % for t he gat or ade gr aphs t o be off which would change our R causing t he I E value t o be slight ly differ ent . 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? Atomic Emission Spectroscopy (AES) I f t he t emperat ur e was incr eased t hat means t hat we ar e also incr easing t he amount of ener gy and when we have mor e energy t he int ensit y will be higher. So t her efor e t he emission int ensit ies woul d be higher if acet ylene-nit r ous oxide was used. 5. Assuming your measured Na concentrations are correct, how accurate is the labelling on the drinks? Calculate and discuss the % error. T he labeling on t he dr inks is more accur at e for t he gat or ade t han it is for t he coke. When I calculat ed t he amount of sodium in t he gat or ade I got 93mg vs t he 110mg t hat was on t he label. The gat or ade label was r elat ively accur at e wit h 15.45% er r or, while t he coca-cola had an 99.6% er r or. For t he coca cola t he label sai d 35mg and when we did t he exper iment we only found 1.43mg. % er r or = (my val ue-act ual)/act ual X 100= 15.45 % for t he gat or ade % er r or = (my val ue-act ual)/act ual X 100= 99.6% er r or for t he cola A r eason for t he huge differ ence fr om what we found vs t he label for t he coke could be t hat t he sodium could be up t o 35mg but n ot mor e. And for t he gat or ade differ ence, t he 110mg could have been an average inst ead of an exact pair ed wit h human er r or in t he act ual int ensit y r eading. 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. 1mL gat orade 4mL cola 0.5844g NaCl 635mL DI wat er Page 6 of 12 Atomic Emission Spectroscopy (AES) 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!) g equation, you is equal to -R is equal to R/nf2. ys and our results to 4 2 1 3 Page 7 of 12 Atomic Emission Spectroscopy (AES) 1 2 3 1 2 3 1 Page 8 of 12 Atomic Emission Spectroscopy (AES) from nf 2 r mole. 2 j/mol 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 Atomic Emission Spectroscopy (AES) 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 Atomic Emission Spectroscopy (AES) 2 2 3 2 2 2 Page 11 of 12 Atomic Emission Spectroscopy (AES) 2 2 1 60 Page 12 of 12 ...
View Full Document

Ask a homework question - tutors are online