MT1-Sp10-v3-KEY - ANSWER KEY Chemistry 4B, Spring 2010...

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ANSWER KEY Page 1 of 7 Chemistry 4B, Spring 2010 February 12, 2010 (50 min., closed book) Name: GSI: SID: Section: Write your name and that of your GSI on all 7 pages of the exam. Equations, constants, and data are provided below. In order to maximize your score on the exam: Do the questions you know how to do first. Circle your final answer. Go back and spend more time on the questions you find more challenging. Budget your time carefully don't spend too much time on one problem. Show all work for which you want credit and don't forget to include units. For the explanation sections, try keep your answers brief as well as complete. Topic Question Page Points Score ICP AES of Cigarettes Q1 4 2 20 ICP AES of Cigarettes Q5 7 3 20 HPLC of Vanillin Q8 4 5 HPLC of Vanillin Q9 12 5 25 EDTA Q13 18 7 30 Useful Equations and Constants: ݁ ൌ ට݁ ൅݁ ൌ ට%݁ ൅%݁ E = h  = c ܰ ܰ ݃ ݃ ݁ ି∆ா ௞் Analyte mobile Anlayte stationary K = C s /C m ܰൌ 16ݐ ݓ ܴ݁ݏ݋݈ݑݐ݅݋݊ ൌ ∆ݐ ݓ ௔௩ pH = log[H 3 O + ] pX = log X Constants: N 0 = 6.02214 x 10 23 mol 1 k b = 1.380 × 10 23 J K 1 h = 6.62607 × 10 34 J s m e = 9.101939 × 10 31 kg c = 2.99792 x 10 8 m s 1 1 nm = 10 9 m = 10 6
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ANSWER KEY Page 2 of 7 ICP AES of Cigarette Ash ICP AES Instrument Setup Copper (Cu) Zinc (Zn) Detected wavelength (nm) 324.754 213.856 Cigarette ash was tested for the presence of heavy metals using ICP AES. A cigarette was lit and allowed to smolder for several minutes. A mass of 0.1054 g of ash was collected and dissolved in 2 mL of concentrated nitric acid, HNO 3 . The solution was filtered and then transferred to a 25.00 mL volumetric flask and diluted to the mark with distilled water. A series of metal standards were prepared and the response to ICP AES was collected. Data for the standards is shown above. 1) The cigarette unknown had an emission intensity of 1.631 × 10 5 for copper. What is the concentration of copper in the final solution of the cigarette ash? ሾCuሿ ൌ ܫ݊ݐ݁݊ݏ݅ݐݕ െ ܫ݊ݐ݁ݎܿ݁݌ݐ ݈ܵ݋݌݁ 163100 െ 4608.7 91270 ൌ ૚. ૠ૜ૠ ppm ሺmg/Lሻ 2) What is the amount of copper ( g) per gram of ash? ݉ Cu ݉ ash ܥ∙ܸ ݉ ash ሺ1.737 mg/Lሻ ∙ ሺ0.02500 Lሻ ሺ0.1054 gሻ ൌ 0.4119 mg/g ൌ ૝૚૚. ૢ μg/g 3) The calibration curve was made from a purchased standard solution with a Cu 2+ ( aq ) concentration of 100.0 ppm ± 1%. What is the concentration of a solution 0.500 mL (±0.006 mL) of standard diluted to a final volume of 100.00mL (±0.08 mL)? Include associated uncertainty.
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This note was uploaded on 03/16/2012 for the course MATH 1B taught by Professor Reshetiken during the Spring '08 term at University of California, Berkeley.

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MT1-Sp10-v3-KEY - ANSWER KEY Chemistry 4B, Spring 2010...

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