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 150.0 mL of solution. The following data were obtained: Absorbance of reagent blank = 0.009 Absorbance of sample = 0.454 Absorbance of sample plus addition – blank = 1.011 Calculate the copper concentration in the sample. Concentration = ____ μg/mL Later studies showed that the reagent blank used to obtain the above data was inadequate and that the actual blank absorbance was 0.060. Find the copper concentration with the appropriate blank, and determine the error caused by using an improper blank. Concentration = _____ μg/mL Error = _____ %

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 150.0 mL of solution. The following data were obtained: Absorbance of reagent blank = 0.009 Absorbance of sample = 0.454 Absorbance of sample plus addition – blank = 1.011 Calculate the copper concentration in the sample. Concentration = __ μg/mL Later studies showed that the reagent blank used to obtain the above data was inadequate and that the actual blank absorbance was 0.060. Find the copper concentration with the appropriate blank, and determine the error caused by using an improper blank. Concentration = _ μg/mL Error = ___ %

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter28: Atomic Spectroscopy

Section: Chapter Questions

Problem 28.15QAP

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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 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.
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.
3. The lead in a swab sample, lead standards, together with a blank were made up in 5.00 mL volumetric flasks using 0.2 % HNO3. 20 μL aliquots of these solutions were injected into the spectrophotometer and the absorbance measured at 217 nm. The following results were obtained. lead / ppb Absorbance 0 0.0591 10.00 0.0858 50.00 0.1926 100.0 0.3260 150.0 0.4594 200.0 0.5929 Swab sample 0.3700 (a) Determine the amount of lead in the swab sample in μg.
In the process of performing a spectrophotometric determination of Fe, an analyst prepares a calibration curve using a single-beam spectrometer, such as a Spec-20. After preparing the calibration curve, the analyst drops the cuvette used for the method blank and the standards. The analyst acquires a new cuvette, measures the absorbance of the sample, and determines the %w/w Fe in the sample. Will the change in cuvette lead to a determinate error in the analysis? Explain.
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.
The determination of iron in wines was carried out by atomic absorption spectrophotometry, using the standard addition method. To do this, 10 mL of wine were placed in five 50 mL volumetric flasks; then 0, 5, 10, 15 and 20 mL of a 10 ppm iron standard solution were added to each of them. Next, they were gauged with distilled water and the absorbance was measured, obtaining the values of 0.040, 0.062, 0.081, 0.102 and 0.125 respectively. Calculate the regression parameters and obtain the iron concentration in the wine, in µg / mL.
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.
0.1040 g of a solid sample containing copper was dissolved by acid and transferred to a 250.00 mL volumetric flask and volume was made up with distilled water. The solution was then diluted by a factor of 20. The final solution was analyzed by atomic absorption spectrophotometry and the concentration was found be 3.109 ppm, What is the weight percentage of copper in the original solid sample? Keep four significant figures in your final answer. Do not try to include the "%" in your answer. e.g. if your final answer is 10.01%, only write 10.01 in the box.
1. An unknown sample of Cu2+ gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 mL of solution containing 100.0 ppm Cu2+ was mixed with 95.0 mL of unknown, and the mixture was diluted to 100.0 mL in a volumetric flask. The absorbance of the new solution was 0.500. a) Denoting the initial unknown concentration as [Cu2+]i, write an expression for the final concentration [Cu2+]f, after dilution. Units of concentration are ppm. b) In a similar manner, write the final concentration of added standard Cu2+ designated as [S]f. c.) Find the [Cu2+]I in the unknown
Quantitative Analysis by External Standard Method Calcium in a juice sample is determined by atomic absorption spectrophotometry. A stock solution of calcium is prepared by dissolving 1.834 g of CaCl, 2H20 in water and diluting to 1000.0 mL. A substock calcium solution was prepared by transferring 10.00 mL of the stock to a 100.00 mL volumetric flask and diluting to the mark. Three standard solutions of calcium were prepared by transferring 2.500 mL. 5.00 mL and 10.00 mL of substock to 50.00 mL volumetric flasks and diluting to the mark. The sample is prepared by transferring 1.000 mL of fruit juice from the original bottle to a 25.00 mL flask and diluting to the mark. Strontium chloride is added to all solutions before dilution to avoid phosphate interference. Instrumental response of the standards is measured against the blank, and the following readings are recorded: 9.10, 18.6 and 37.0. The sampie reading is 28.1. Using the multipoint method, find the concentration of calcium in…
0.1120 g of a solid sample containing copper was dissolved by acid and transferred to a 250.00 mL volumetric flask and volume was made up with distilled water. The solution was then diluted by a factor of 25. The final solution was analyzed by atomic absorption spectrophotometry and the concentration was found be 2.982 ppm, What is the weight percentage of copper in the original solid sample? Keep four significant figures in your final answer.