Chem152_Post Lab 6.xls

Sheet1 Name Qz Section 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 Part I. Measuring the Hydrogen Emission Spectrum 5 DATA Table 1. Hydrogen Emission Data Spectroscope Data Ocean Optics Spectrometer Color Wavelength, nm l (nm), descending order violet 430 658.6 blue-green 482 487.6 red 660 435.2 411.2 397.9 A: Data Analysis Table 2. Hypothesis #1; nf = 1; ni = 2, 3, 4, 5, 6 ni values 1/ni2 l (nm) 1/l nm-1 2 0.25000 658.6 0.00152 3 0.11111 487.6 0.00205 4 0.06250 435.2 0.00230 1 5 0.04000 411.2 0.00243 6 0.02778 397.9 0.00251 2 Slope: -0.0044 R from slope: 0.0044 nm-1 Is nf=1? no y-intercept: 0.0026 R from y-intercept: 0.0026 nm-1 3 Table 3. Hypothesis #2; nf = 2; ni = 3, 4, 5, 6, 7 ni values 1/ni2 l (nm) 1/l nm-1 3 0.11111 658.6 0.00152 4 0.06250 487.6 0.00205 5 0.04000 435.2 0.00230 1 6 0.02778 411.2 0.00243 7 0.02041 397.9 0.00251 2 Slope: -0.011 R from slope: 0.011 nm-1 Is nf=2? yes y-intercept: 0.0027 R from y-intercept: 0.0108 nm-1 3 Table 4. Hypothesis #3; nf = 3; ni = 4, 5, 6, 7, 8 ni values 1/ni2 l (nm) 1/l nm-1 4 0.06250 658.6 0.00152 5 0.04000 487.6 0.00205 6 0.02778 435.2 0.00230 1 7 0.02041 411.2 0.00243 8 0.01563 397.9 0.00251 2 Slope: -0.0213 R from slope: 0.0213 nm-1 Is nf=3? no y-intercept: 0.0029 R from y-intercept: 0.0261 nm-1 3 Summary of information to be used in the next section (from the data for the correct nf value above): R (in SI units) 1.100E07 m-1 b (in SI units) 2.7000E06 m-1 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. h (Planck's const) c (speed of light) IE(per atom) 6.62600E-34 3.000000E08 5.3671E-19 2 Js 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, to the IE just calculated. This energy term is equal to 3/4hcR for nf=2 and 8/9 hcR for nf=3. Calculate IE from ground state (nf = 1) here, both per atom and per mole: IE(per atom) 1.6399E-18 J 2 Avogadro's # 6.02200E23 mole -1 IE (per mole) 9.8757E05 J/mole 2 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 h, c, and R will autofill from B150, C150, and B141, respectively, so you just need to enter the formula in Column F to calculate En. En n h c R En(J) Ea ? 6.62600E-34 3.000000E08 1.100E07 #VALUE! E4 4 6.62600E-34 3.000000E08 1.100E07 -1.367E-19 2 E3 3 6.62600E-34 3.000000E08 1.100E07 -2.430E-19 E2 2 6.62600E-34 3.000000E08 1.100E07 -5.466E-19 E1 1 6.62600E-34 3.000000E08 1.100E07 -2.187E-18 Part II. An Application of AES; Determination of Sodium DATA Molar mass of NaCl 58.44 g/mole Calculated mass of NaCl needed to make 100 mL of 0.100M 0.5844 g Actual mass of NaCl weighed out 0.584 g mL of 0.100 M needed to make Standards 1 - 5 Standard 1 (0.0010 M) 1.00 Standard 2 (0.00080 M) 0.80 Standard 3 (0.00060 M) 0.60 Standard 4 (0.00040 M) 0.40 Standard 5 (0.00020 M) 0.20 1 Table 5: FLAME PHOTOMETER MEASUREMENTS DATA Sample [Na+], (M) [Na+], (mg/8 fl oz) Intensity Standard 1 0.00100 0.03 100 Standard 2 0.00080 0.02 90 Standard 3 0.00060 0.02 72 1 Standard 4 0.00040 0.01 57 Standard 5 0.00020 0.01 41 Sample Dilution Factor Intensity Gatorade 25 76 Coca Cola 2.5 31 Site #1, 8.5 m depth 1 64 Site #1, 9.5 m depth 2 65 Site #1, 10.5 m depth 10 75 Site #1, 11.5 m depth 100 44 Seawater 400 93 DATA ANALYSIS 2 slope 7.56E04 M-1 y-intercept 26.67 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? See box. 89 mg/8 fl. oz, sports drink 110 mg/8 fl.oz on label 81 % measured vs labeled values 2 1 mg/8 fl. oz. for the cola drink 35 mg/8 fl.oz on label 3 % measured vs labeled values 3 Freshwater samples as a function of depth: Depth (m) Intensity Dilution Factor Concentration (M) 8.5 64 1 0.00049 9.5 65 2 0.00101 1 10.5 75 10 0.00639 11.5 44 100 0.02293 2 At the deepest point, what is the ratio of Seawater to Freshwater? What about the most shallow point? Dilution Factor Intensity Concentration (M) Seawater 400 93 0.35100 Dilution Factor = [Na Seawater]/[Na Freshwater, deepest point or most shallow point] deepest 15.3 most shallow 716 2 3 RESULTS AND DISCUSSION 2 2 2 2 2 1 60 Page &P of &N Sheet2 Sheet3