Copper was determined in a river water sample by atomic absorption spectrometry and the method of standard additions. For the addition, 100.0 mL of a 1000.0-mg/mL Cu standard was added to 100.0 mL of solution. The following data were obtained: Absorbance of reagent blank 5 0.020 Absorbance of sample 5 0.520 Absorbance of sample plus addition 2 blank 5 1.020 (a) Calculate the copper concentration in the sample. (b) Later studies showed that the reagent blank used to obtain the above data was inadequate and that the actual blank absorbance was 0.100. Find the copper concentration with the appropriate blank, and determine the error caused by using an improper blank.

Copper was determined in a river water sample by atomic absorption spectrometry and the method of standard additions. For the addition, 100.0 mL of a 1000.0-mg/mL Cu standard was added to 100.0 mL of solution. The following data were obtained: Absorbance of reagent blank 5 0.020 Absorbance of sample 5 0.520 Absorbance of sample plus addition 2 blank 5 1.020 (a) Calculate the copper concentration in the sample. (b) Later studies showed that the reagent blank used to obtain the above data was inadequate and that the actual blank absorbance was 0.100. Find the copper concentration with the appropriate blank, and determine the error caused by using an improper blank.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter10: Atomic Emission Spectrometry

Section: Chapter Questions

Problem 10.11QAP

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Copper was determined in a river water sample by atomic absorption spectrometry and the method of standard additions. For the addition, 100.0 µL of a 1000.0 µg/mL Cu standard was added to 100.0 mL of solution. The following data were obtained: Absorbance of reagent blank = 0.020 Absorbance of sample = 0.520 Absorbance of sample plus addition – blank = 1.020 Calculate the copper concentration in the sample.
A water sample was analyzed for Fe content using the iron- phenanthroline method. The following data were obtained from the analysis: Reagent Blank Absorbance Absorbance (au) Reagent Blank Absorbance 0.003 Concentration of Stock Solution: 10 ppm Volume of Stock Solution (mL) Total Volume of Standard Solution Concentration of Standard Solution (ppm) Absorbance (au) (mL) 0.50 10.00 0.012 1.00 10.00 0.132 2.00 10.00 0.267 3.00 10.00 0.349 4.00 10.00 0.428 5.00 10.00 0.560 Volume of Unknown Solution Total Volume of Unknown Solution Trial Absorbance (au) (mL) (mL) 1 5.00 10.00 0.289 2 5.00 10.00 0.296 3 5.00 10.00 0.281 Determine the value of the slope (m), y-intercept (b), and the coefficient of determination (r²) A m = 0.1128; b = -4.0 x 10-5; r2 = 0.9880 B m = 0.1128; b = -4.0 x 10-5; r² = 0.9762 C) m = 0.1128; b = -3.0 x 10-³; r² = 0.9880 D m = 0.1128; b = -3.0 x 10-³; r² = 0.9762
To quantify the Cadmium content in a water sample, 5 aliquots of 10 mL were taken, adding to each one of them a volume of a standard solution of Cd (2 mg / mL); after the addition the final volume for all solutions was 50 mL. The absorbance reading was taken in an Atomic Absorption spectrophotometer, the data recorded were: Aliquot 1 2 3 4 5 Cd solution (mL) 0 1 2 3 4 Absorbance 0.163 0.240 0.319 0.402 0.478 Calculate the ppm of Cd.
7. A Cu2* solution obtained by dissolving a 3.1871-g penny in 500 mL of nitric acid has an absorbance of 0.342 at 620 nm in a 1.00 cm cell. The calibration curve prepared from Cu2+ solutions of varying concentrations has a slope of 281.8 L/mol and a y-intercept of 0.0106. (a) Calculate the concentration of the solution in moles per liter. (b) Calculate the percent Cu by mass in the penny
With reference to the following calibration curve, what is the concentration (M) of a solution with absorbance of 0.3? Abs 0.5 0.4 0.3 0.2 0.1 0.2 0.4 0.6 Concentration (M) A 0.2 M В 0.3 М (c) 0.4 М D 0.5 M
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
A 10.0-mL aliquot of a standard manganese solution containing 62.5 mg/L of Mn is oxidized to MnO4- and diluted to 50.0 mL in a volumetric flask. The absorbance is measured in a 1.00-cm cell at 525 nm is 0.343. Next, a 850-mg steel sample containing manganese in dissolved in acid and diluted to 250 mL. A 50.0-mL aliquot is treated with KIO4 to oxidize Mn to MnO4- and diluted to 100.0 mL. If the absorbance at 525 nm is 0.468 in a 1.00-cm cell, calculate the weight percent of Mn in the steel.
(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.
Fe+3 (aq) + SCN – (aq) FeSCN +2 (aq) She mixes 4.00 mL of 2.00 mM SCN– and 5.00 mL of 2.00 mM Fe+3 ions, then diluting with 1.00mL of water to give a total volume of 10.00mL. She measures the absorbance of the solution asbeing 0.210. If she has previously calculated the molar absorbtivity constant (ε) of the product tobe 2583 cm–1 M–1, what is her best estimate for the K value for this reaction?
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 solution of Ba(OH)2 was standardized against0.1215 g of primary-standard-grade benzoic acid, C6H5COOH (122.12 g/mol). An end point was observedafter addition of 43.25 mL of base. (a) Calculate the molar concentration of the base. (b) Calculate the standard deviation of the molarconcentration if the standard deviation for themass measurement was ±0.3 mg and that for thevolume measurement was ±0.02 mL. (c) Assuming an error of ±0.3 mg in the mass measurement,calculate the absolute and relative systematicerror in the molar concentration.
Ine density Calculate the molarity of solution prepared by weighing 6.34 g of NaOH using a balance with a standard deviation of ± 0.05 g and dissolving it in a 500 mL of water in a volumetric flask with a standard deviation of ± 0.2 mL.