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.

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter12: Spectrochemical Methods

Section: Chapter Questions

Problem 12P

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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.
An unknown sample of Cu2+ gave an absorbance of 0.475 in an atomic absorption analysis. Then 5.00 mL of solution containing 75.0 ppm (= µg/mL) Cu2+ was mixed with 45.0 mL of unknown, and the mixture was diluted to 500.0 mL in a volumetric flask. a) Write an expression for the final concentration after dilution. b) Calculate the final concentration of the added standard. c) The absorbance of the new solution was 0.987. Find the initial concentration of Cu2+ in the unknown sample
Six 10.00 mL samples of raw milk were treated with 0, 5.00, 10.00, 15.00, 20.00, and 25.00 µg of zinc ion and diluted to 50.00 mall The absorbances of these solutions were 0.235, 0.292, 0.346, 0.397, 0.458 and 0.510. a) Identify the calibration method used. (Standard Addition, Internal Standard, or External Standard?) b) Calculate the ppm Zn in the sample of milk.
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.
Ben ran through the experiment and found the best-fit line listed below for his standard calibration curve of absorbance vs concentration in M. y = 3214.0x + 0.0076 Ben then prepared a solution that had 5.00 mL 0.002 M iron(III) nitrate in 1 M nitric acid, 3.00 mL 0.002 M potassium thiocyanate, and 2.00 mL DI water. If the absorbance for the solution was 0.436, calculate the equilibrium concentration of iron(III) thiocyanate in the solution. Report your answer in mM with three places after the decimal.
Preparing a standard curve. 1. determine the absorbance max of [FeSCN]2+ it is 448.1 2. determine the concentration of FeSCN2+ in the stock solution. M1V1=M2V2 stock solution: ~0.200 M iron (iii) nitrate in 1M nitric acid intial volume: 0.3mL final volume: 10.3mL volume: 10mL ~0.002M potassium thiocyanate initial volume: 0.3mL final volume: 10.3mL volume: 10mL not sure if this is needed stock solutions: ~0.200M iron (iii) nitrate in 1M nitric acid: 0.207M ~0.002M iron (iii) nitrate in 1M nitric acid: 0.00209M ~0.002M potassium thiocyanate: 0.00193M
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.
A graphite furnace atomic absorption spectrophotometer (AAS) was used to determine the arsenic (As) concentrations in drinking water. A large set of blank samples yielded an average blank signal of 0.013 and a blank standard deviation of 0.0030. The following data were obtained for a calibration curve. [As] (ppm) 2.0 4.0 6.0 8.0 10.0 Absorbance 0.17 0.28 0.48 0.53 0.72 Using a spreadsheet on an Excell, create a graph of the data using symbols only for the data points. Plot the line on the same graph and include the graph to this question. (a). What is the sensitivity of the method? (b). Calculate the LOD and LOQ for As. (c). A sample of water yielded an absorbance of 0.43. What is the concentration of As in the water?
Quinine in a 1.553-g antimalarial tablet was dissolved in sufficient 0.10 M HCl to give 250 mL of solution.A 10.00-mL aliquot was then diluted to 50.00 mL with the acid. The fluorescence intensity for the dilutedsample at 347.5 nm provided a reading of 196 on an arbitrary scale. A standard 100-ppm quinine solutionregistered 125 when measured under conditions identical to those for the diluted sample. Calculate the massin milligrams of quinine in the tablet.
An unknown concentration of [FeSal]+ gave an absorbance reading of 0.301. Calculate the concentration of the solution, given that the slope of the standard curve was 1280 and the y intercept was -0.00821.
The nitrate in water was analyzed using a spectrophotometric method. The absorbances of the standards and the unknown sample were obtained at 550 nm.Solution Absorbance 2.00 µM 0.0656.00 µM 0.20510.00 µM 0.33814.00 µM 0.47418.00 µM 0.598Unknown 0.402 Write the equation of the lineWhat is the standard deviation of the calibration curve?
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+Fe(SCN)2+ solution with an unknown concentration and an absorbance value of 0.4150.415 . The slope-intercept form of the equation of the line is ?=4558.4?+0.0147y=4558.4⁢x+0.0147 . The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe3+Fe3+ concentration of the unknown solution?