2. A spectrophotometric method for the quantitative determination of the concentration of Pb in blood uses Cu* as an internal standard. A solution was prepared by combining 2.50mL of 7.000ppb Pb* with 1.000ml of 22.50ppb Cu the mixture was then diluted to 10.00mL. Which give an absorbance signal of 3.20 for lead and 1.35 for the copper. A 5.00mL sample of blood with unknown concentration of Pb?* is spiked with 1.000ml of 22.5ppb Cu and diluted to 10.00mL the resulting solution gave a signal of 4.95 for lead and 2.75 for copper. What is the concentration of lead in the blood sample?

2. A spectrophotometric method for the quantitative determination of the concentration of Pb in blood uses Cu* as an internal standard. A solution was prepared by combining 2.50mL of 7.000ppb Pb* with 1.000ml of 22.50ppb Cu the mixture was then diluted to 10.00mL. Which give an absorbance signal of 3.20 for lead and 1.35 for the copper. A 5.00mL sample of blood with unknown concentration of Pb?* is spiked with 1.000ml of 22.5ppb Cu and diluted to 10.00mL the resulting solution gave a signal of 4.95 for lead and 2.75 for copper. What is the concentration of lead in the blood sample?

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter12: Spectrochemical Methods

Section: Chapter Questions

Problem 7P

See similar textbooks

Similar questions

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?
For Indirect Iodometric Analysis of Copper... ~0.0896g KIO3 necessary to consume 350mL of 0.1 M Na2S2O3, Na2S2O3 is stored in an amber glass bottle until ready for use. Primary Standard KIO3 has 2g of KI, 50mL of DI water, and 10 mL of 1.0M HCl is added then immediately titrated with Na2S2O3 until medium yellow or straw... then 5mL of starch indicator is added and titrated again until blue black color turns clear. Unknown CuO use 1.2G of Unknown, 20mL of HNO3 heated until sample dissolved, 25 mL of DI water added and boiled until clear light blue color, after cooling 1:1 NH3 added (~34.47 mL of NH4OH reagent) until permanent deep blue color amine complex, 2g of NH4HF2 added and swirled until dissolved, 3 g of KI is added then titrated immediately with Na2S2O3 until brown color of iodide is nearly gone (brown milk color), 2 g of KSCN and 3 mL of starch indicator is then added with titration continuing until disappearance of new blue black color. 1. Na2CO3 is often added to thiosulfate…
For Indirect Iodometric Analysis of Copper... ~0.0896g KIO3 necessary to consume 350mL of 0.1 M Na2S2O3, Na2S2O3 is stored in an amber glass bottle until ready for use. Primary Standard KIO3 has 2g of KI, 50mL of DI water, and 10 mL of 1.0M HCl is added then immediately titrated with Na2S2O3 until medium yellow or straw... then 5mL of starch indicator is added and titrated again until blue black color turns clear. Unknown CuO use 1.2G of Unknown, 20mL of HNO3 heated until sample dissolved, 25 mL of DI water added and boiled until clear light blue color, after cooling 1:1 NH3 added (~34.47 mL of NH4OH reagent) until permanent deep blue color amine complex, 2g of NH4HF2 added and swirled until dissolved, 3 g of KI is added then titrated immediately with Na2S2O3 until brown color of iodide is nearly gone (brown milk color), 2 g of KSCN and 3 mL of starch indicator is then added with titration continuing until disappearance of new blue black color. 4. Why is the starch indicator solution…
A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness and quantitatively transferred to a 250 mL volumetric flask, and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was performed and was determined to be 0.4 mL. What is the concentration of EDTA obtained (MW CaCO3 = 100.0869 g/mol)?
A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness, and quantitatively transferred to a 250 mL volumetric flask and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. [Analysis] A 30 mL unknown water sample was treated with 37.6 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. What is the concentration of Ca2+ (40.0780 g/mol) in ppm?
A 0.4020 g sample was dissolved, and Ca2+ and Ba2+ ions present were precipitated as Ba.C2O4.H2O and CaC2O4H2O. The Oxalates were then heated in a thermogravimetric apparatus leaving a residue that weighed 0.3175 g in the range of 320°C to 440°C and 0.2165 g in the range of 580°C to 620°C. Calculate percentage Ca and percentage Ba in the sample.
A foot powder sample containing Zn was dissolved on 50.00 mL water and was titrated to the end point color with 22.57 mL of 0.01639 M EDTA at pH=4. (α= 3.61x109, KKzny2 = 3.2 x 1016). The pZn in the sample is:
A 0.6025 g sample was dissolved and the Ca2+ and Ba2+ ions present were precipitated as BaC2O4.H2O and CaC2O4.H2O. The oxalates were then heated in a thermogravimetric apparatus leaving a residue that weighed 0.5713 g in the range 320oC to 400oC and 0.4674 g in the range 580oC to 620oC. Calculate the percentage Ba in the sample.
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.
Lead in dry river sediment was extracted with 25 wt% HNO3 at incubation temperatures for 1 hr. Then 1 mL of filtered extract was combined with other reagents to a total of 4.60 mL. Pb+2 was measured by an electrochemical method by spiking with 2.50 ppm Pb2+. added vol. of 2.50ppm Pb2 signal 0 mL 1.10 0.025 mL 1.66 .050 mL 2.20 .075 mL 2.81 what is Sx based on Sy
A 30.00-L air sample was passed through an absorption tower containing a solution of Cd+2, where H2S was retained as CdS. The mixture was acidified and treated with 10.00 mL of 0.01070 M I2. After the reaction: S-2 + I2 S(s) + 2 I- was complete, the excess iodine was titrated with 12.85 mL of 0.01344 M thiosulfate. Calculate the concentration of H2S in ppm (w/w); use 1.20 g/L for the density of the gas stream. Molar Mass: H2S = 34.082
A third spectrophotometric method for the quantitative analysis of Pb2+ in blood uses Cu2+ as an internal standard. A standard containing 1.75 ppb Pb2+ and 2.25 ppb Cu2+ yields a ratio of (SA/SIS)std of 2.37. A sample of blood is spiked with the same concentration of Cu2+, giving a signal ratio, (SA/SIS)samp, of 1.80. Determine the concentration of Pb2+ in the sample of blood.