An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd+ content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 "C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 91.79 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0 ml. of 0.1 M HCI to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.0 ml. volumetric flasks, cach containing 5.00 ml. aliquots of the sample solution. Varying amounts of a 85.0 ppb (ug/L.) Cd standard were added to cach of the flasks, which were then brought to volume with D.I M HCL The Cd content of the solutions was then analyzed using GFAAS, resulting in the absorbance data given in the table. Ca Standard Volume Sample Volume (mL) Absorbance (mL)

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd+ content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 "C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 91.79 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0 ml. of 0.1 M HCI to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.0 ml. volumetric flasks, cach containing 5.00 ml. aliquots of the sample solution. Varying amounts of a 85.0 ppb (ug/L.) Cd standard were added to cach of the flasks, which were then brought to volume with D.I M HCL The Cd content of the solutions was then analyzed using GFAAS, resulting in the absorbance data given in the table. Ca Standard Volume Sample Volume (mL) Absorbance (mL)

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter27: Molecular Fluorescence Spectroscopy

Section: Chapter Questions

Problem 27.9QAP

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(Standard addition) Tooth enamel consists mainly of the mineral calcium hydroxyapatite, Ca10(PO4)6(OH)2. Trace elements in teeth of archeological specimen provide anthropologists with clues about diet and diseases of ancient people. Student at Dankook University measured the trace element strontium (Sr) in enamel from extracted wisdom teeth by atomic absorption spectroscopy. Solutions were prepared with a constant total volume of 10 mL containing 0.750 mg dissolved tooth enamel plus variable concentrations of added standard Sr. Added Standard Sr (ng/mL=ppb) 0 2.50 5.00 7.50 10.00 Emission Signal 28.0 34.3 42.8 51.5 58.6 (a) Make a graph showing the experimental data and the calculated straight line. (b) Find the concentration of Sr in the tooth ennamel in parts per million = μg/mL.
A student prepared four standard solutions of (NH4)2Fe(SO4)2 and measured their absorbance at 505 nm. She created a calibration plot with the best-fit line of y = 9372 x + 0.0539. She measured the absorbance of her diluted unknown sample solution as (4.69x10^-1) nm. If she prepared her diluted sample solution by diluting 10.00 mL of the original solution to a total volume of 50.00 mL with deionized water, what is the concentration of Fe2+ in her original solution? Answer in units of M. Note: Your answer is assumed to be reduced to the highest power possible.
A 10.00 mL of natural water sample containing Ni2+ was pipetted into a volumetric flask and diluted to 50.00 mL with pure water. In the second 10.00 mL of natural water sample transferred into a volumetric flask, exactly 4.00 mL of a Ni2+ solution with a concentration of 5.99 mg/L was added and then diluted to 50.00 mL with pure water. The measured absorbance is A1= 0.436 and A2 = 0.663. What is the Ni2+ concentration in unit of mg/L in the natural water sample?
As part of an analytical chemistry laboratory course, a student measured the Ca2+ content in two water samples, city-supplied drinking water and well-supplied drinking water, using two different analytical methods, flame atomic absorption spectrometry (FAAS) and EDTA complexometric titration. The results of this experiment are given in the table as the mean Ca2+concentration (?¯) and standard deviation (?) in parts per million (ppm). Each sample was measured five times (n=5) by each method. Method City-Supplied Drinking Water (?¯±?x¯±s) Well-Supplied Drinking Water (?¯±?x¯±s) FAAS 57.57±0.68 ppm 64.77±0.70 ppm EDTA titration 58.32±0.96 ppm 65.62±0.97 ppm Method Comparison: For each drinking water sample (city and well), compare the Ca2+ content measured by FAAS and EDTA titration. Calculate the ? value for each sample. Do the methods produce statistically different results at the 95% confidence level when measuring the Ca2+content of the city-supplied drinking water? Do the…
Note: the graph should be absorbance as a function of the concentration of Cu standard after final dilution, not volume. explain in detail.
Commercial Vanadyl Sulfate (VOSO4) is contaminated with H2SO4 and H2O. A solution was prepared dissolving 0.2447 g of impure VOSO4 in 50.00 mL of water. A spectrophotometric analysis indicated that the The concentration of vanadyl ions, VO2+ (blue) was 0.0243 M. A 5.00 mL sample was passed through a column filled with a cation exchange resin in H+ form, to retain the vanadyl ion and the eluent necessary for its titration 13.03 mL of NaOH 0.02274 M. Calculate the percentage by weight of each component (VOSO4, H2SO4, and H2O) in commercial vanadyl sulfate. (Pm VOSO4, 162.96; H2SO4, 97.94)
A spectrophotometric method for the quantitative determination of the concentration ofPb2+ in blood yields an Ssamp of 0.133 for a 1 mL sample of blood that has been diluted to 6 mL. A second sample is spiked with 1 µL of a 1467 ppb Pb2+ standard and diluted to 6 mL, yielding an Sspike of 0.491. Determine the concentration of Pb2+ in the original sample of blood.
The protein concentration of a protein isolate was determined using the Bradford assay. Five dilution of bovine serum albumin (BSA) were prepared from a 5.00 mg/mL BSA stock solution. To these dilutions, 100 µl of Bradford reagent were added. After 5 minutes, the absorbance was taken at 595 nm. Standard # BSA, in mg/mL Volume of Bradford reagent, A595 in mL 1 5.0 0.000 1.00 5.0 0.134 3 2.00 5.0 0.265 4 3.00 5.0 0.388 4.00 5.0 0.497 The supernatant dilution was prepared by mixing 49 µL of the protein isolate with 16 µL water. The absorbance was taken 5 minutes after addition of 100 mL Bradford reagent. Calculate the protein concentration (in mg/mL) of the original isolate if the absorbance at 595 nm was 0.413. Note: Final answer format must be x.xxx (three decimal places). Round off only in the final answer. Do not round off in the middle of calculation.
4- A sample containing H2C204 had a purity equal to 90.50% (w/w). An unknown mass of this sample was dissolved in water and transferred to a 50.00 mL flask. An aliquot of 25.00 mL was transferred to an erlenmeyer flask and 50.00 mL of a 0.2000 mol L^-1 NaOH solution were added. %3 Excess NaOH was titrated with 0.09000 mol L^-1 HCI solution using 2.000 mL. Calculate the mass (g) of the sample used. Data: H = 1.008 C= 12.01 O = 16.00
The content of manganese (Mn) in steel was determined spectrophotometrically and with the use of the standard addition method. An unknown sample of Mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. When 5.00 mL of solution containing 95.5 ppm Mn was added to 50.0 mL of the unknown steel solution (digested sample), the absorbance was 0.248. Calculate the concentration, in parts-per-million (ppm), of Mn in the digested steel sample solution. NOTE: When a problem does not state diluted to a given volume, then you consider the sum of the volumes for Vf. A. 9.55 B. 20.2 C. 5.68 D. 140 E. 22.1 F. 96.7 G. 6.95
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The standard curve was made by spectrophotographic analysis of equilibrated iron(III) thiocyanate solutions of known concentration. You are asked to analyze a Fe(SCN)2+ solution with an unknown concentration and an absorbance value of 0.392. The slope-intercept form of the equation of the line is y = 4538.1x +0.0077. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe³+ concentration of the unknown solution? [Fe³+] = mol/L Absorbance Iron(III) thiocynate standard curve 1.0 V 0.5 0.0001 Fe³+ concentration (M) 0 0.0002