in a standard addition calibration method, 50.0 ml volumetric flasks were used. A 5.0 ml aliquot of a solution containing penobarbital was put in each. The solutions were made basic with KOH and mixed with different increments of 2.0 ppm standard penobarbital. The volumes were adjusted to 50,0 ml and absorbances were measured as follows Volume added (ml) 0.00 0.50 1.00 1.50 2.00 Absorbance 0.33 0.48 0.64 0.80 0.96 Calculate the concentration of phenobarbital in the unknown (Use graphical or numerical solutions)

in a standard addition calibration method, 50.0 ml volumetric flasks were used. A 5.0 ml aliquot of a solution containing penobarbital was put in each. The solutions were made basic with KOH and mixed with different increments of 2.0 ppm standard penobarbital. The volumes were adjusted to 50,0 ml and absorbances were measured as follows Volume added (ml) 0.00 0.50 1.00 1.50 2.00 Absorbance 0.33 0.48 0.64 0.80 0.96 Calculate the concentration of phenobarbital in the unknown (Use graphical or numerical solutions)

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

Chapter9: Atomic Absorption And Atomic Fluorescence Spectrometry

Section: Chapter Questions

Problem 9.22QAP: The chromium in an aqueous sample was determined by pipetting 10.0 ml. of the unknown into each of...

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The chromium in an aqueous sample was determined by pipetting 10.0 ml. of the unknown into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cr were added to the flasks, following which the solutions were diluted to volume. Unknown,mLStandard, mLAbsorbancc 10.00.00.201 10.010.0 0.292 10.020.0 0.378 10.030.0 0.467 10.040.0 0.554 (a) Plot the data using a spreadsheet. (b) Determine an equation for the relationship between absorbance and volume of standard. (c) Calculate the statistics for the least-squares relationship in (b). (d) I)ctcrmine the conccnt ration oÍCr in ppm in the sample. (e) Find the standard deviation of the result in (d).
The acid-base indicator HIn undergoes the following reaction in dilute aqueous solution: HIncolor1H++Incolor2 The following absorbance data were obtained for a 5.00 I0-4 M solution of HIn in 0.1 M NaOH and 0.1 M HC1. Measurements were made at wavelengths of 485 nm and 625 nm with 1.00-cm cells. 0.1 M NaOH A485 = 0.075 A625 = 0.904 0.1 M HC1 A485 = 0.487 A625 = 0.181 In the NaOH solution, essentially all of the indicator is present as In-; in the acidic solution, it is essentially all in the form of HIn. (a) Calculate molar absorptivities for In- and HIn at 485 and 625 nm. (b) Calculate the acid dissociation constant for the indicator ¡fa pH 5.00 buffer containing a small amount of the indicator exhibits an absorbance of 0.567 at 485 nm and 0.395 at 625 nm (1.00-cm cells). (c) What is the pH of a solution containing a small amount of the indicator that exhibits an absorbance of0.492 at 485 nm and 0.245 at 635 nm (1.00-cm cells)? (d) A 25.00-mL aliquot of a solution of purified weak organic acid HX required exactly 24.20 mL of a standard solution of a strong base to reach a phenolphthalein end point. When exactly 12.10 mL of the base was added to a second 25.00-mL aliquot of the acid, which contained a small amount of the Indicator under consideration, the absorbance was found to be 0.333 at 485 nm and 0.655 at 625 nm (1.00-cmcells). Calculate the pH of the solution and Ka for the weak acid. (e) What would be the absorbance of a solution at 485 and 625 nm (1.50-cm cells) that was 2.00 10-4 M in the indicator and was buffered to a pH of 6.000?
A liquid sample was analyzed for Fe³+. A plot of absorbance (y-axis) vs. concentration (ppm; x-axis) of the external standards produced a calibration line with an equation y = 0.2256x -0.0903 (R² = 0.9973). The absorbance of the sample was 1.25. Determine the amount of Fe³+ in the sample (in ppm).
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.
1 mL was taken from the sample filtrate and mixed with 13 mL pure water and 4 mL sulfomolybdic acid and 2 mL dilute SnCI2 solution by adding it, and after waiting for 15 minutes, the absorbance of the resulting solutions against pure water was read at 520 nm. if the function of the calibration graph obtained with standard phosphorus solutions of 0.5-2.5 mg/mL is y= 0.245x + 0.107 and the absorbance of the serum sample is 0.342, how many grams of phosphorus is the amount in the sample?
In spectrophotometric analysis, the relationship between the absorbance A and the analyte's concentration C is: A = ebC + Ablank What is the molar extinction coefficient I and its absolute uncertainty if A is 0.68 ± 0.06; Ablank is 0.06 ± 0.01; b is 1.00 cm; and C is (0.45 ± 0.03)x10-5 mol/L?
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.
In the determination of lead content in a solid food sample, 1 g of the solid food sample was extracted with 10 mL of solvent and then diluted to a final volume of 50 mL. A calibration plot of lead standards was obtained from the standard solutions of 1 to 50 ug/mL and it gave a linear regression line of y = 0.025x + 0.004. The wavelength for lead analysis is 283.3 nm. The absorbance value for the extract was 0.302 arbitrary units. Calculate the percentage of Pb in 1 g of the solid food sample.
Quinine in a 1.664 g antimalarial tablet was dissolved in sufficient 0.10 M HCl to give 500 mL of solution. A 15.00 mL aliquot was then diluted to 100.0 mL with the acid. The fluorescense intensity for the diluted sample at 347.5 nm provided a reading of 288 on an arbitrary scale. A standard 100 ppm quinine solution registered 180 when measured under conditions identical to those for the diluted sample. Calculate the mass in milligrams of quinine in the tablet.
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.
. 100 ml boiled cooled and filtered water sample takes 9.6 ml of M/50 EDTA in titration. The Permanent hardness of the water sample in terms of ppm of CaCO3 equivalent is
A 10.00 g sample containing an analyte was transferred to a 250 mL volumetric flask and diluted to volume. When a 10.00 mL aliquot of the resulting solution was diluted to 25.00 mL it was found to give a signal of 0.235 (arbitrary units). A second 10.00 mL aliquot was spiked with 10.00 mL of a 1.00 ppm standard solution of the analyte and diluted to 25.00 mL. The signal for the spiked sample was found to be 0.502. Calculate the weight percent of analyte in the original sample.