2. Consider the following experiment. Twenty mL of a 1.00 M HCl solution is added to 100 mLof a 0.100 M aqueous solution of sodium thiosulfate. After 40 seconds, the reaction hasproduced enough sulfur to cause a decrease in the percent transmittance to 90%T. If thisreaction is repeated using 0.05 M sodium thiosulfate, how long should it take for the reactionmixture to give a 90%T reading if the reaction is first order with respect to Na2S2O3? Secondorder? Third order? Explain.

2. Consider the following experiment. Twenty mL of a 1.00 M HCl solution is added to 100 mL of a 0.100 M aqueous solution of sodium thiosulfate. After 40 seconds, the reaction has produced enough sulfur to cause a decrease in the percent transmittance to 90%T. reaction is repeated using 0.05 M sodium thiosulfate, how long should it take for the reaction mixture to give a 90%T reading if the reaction is first order with respect to NazS2O3? Second order? Third order? Explain. If this

2. Consider the following experiment. Twenty mL of a 1.00 M HCl solution is added to 100 mL of a 0.100 M aqueous solution of sodium thiosulfate. After 40 seconds, the reaction has produced enough sulfur to cause a decrease in the percent transmittance to 90%T. reaction is repeated using 0.05 M sodium thiosulfate, how long should it take for the reaction mixture to give a 90%T reading if the reaction is first order with respect to NazS2O3? Second order? Third order? Explain. If this

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

Chapter13: An Introduction To Ultraviolet-visible Molecular Absorption Spectrometry

Section: Chapter Questions

Problem 13.14QAP

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Fluorescence intensity was taken of 2.0 mL of the 10 μg/mL quinine standard solution into five 25 mL volumetric flasks. Into one, place 1.0 mL of 0.05 M sodium bromide solution and dilute to the mark with 0.05 M sulfuric acid solution. Similarly, add 2.0, 4.0, 8.0, and 16.0 mL of the sodium bromide solution to the remaining flasks before diluting to volume with the sulfuric acid solution. Why did the fluorescence intensity decrease as the concentration of sodium bromide increased? Only typed and correct answer with explanation please
The measurement of Li in brine (salt water) is used by geochemists to help determine the origin of this fluid in oil fields. Flame atomic absorption of Li is subject to interference by other elements. Atomic absorption of analysis of replicate sample of Li in a brine sample gave results in the table. a. Suggest a reason for the increasing apparent concentration of Li from sample 1 to 2. b. Suggest a reason for the increasing apparent concentration of Li from sample 1 to 3 c. Why do samples 4-6 give a nearly constant result? (What type of interference you think is being eliminated?
UV-Visible spectroscopy is used to determine the content of an analyte in a capsule. Weigh 100.0 mg of the capsule contents (total weight of contents 500 mg), add 2.0 mL of 0.05 M NaOH, filter the flask, and make up to 25.00 mL with NaOH. The measured transmittance of this solution is 33.0%. The analyte standard is prepared by dissolving 10.0 mg of standard in 25.00 mL of 0.05 M NaOH, then taking 10.00 mL of that solution and diluting to a final volume of 50.00 mL where the transmittance is obtained from 44.0%. Calculate the content of the analyte in the capsule.
A set of three replicate AAS measurements were made from the same calcium standard. Use the information below to determine the LOD for calcium analysis. ⚫ The standard was prepared by dissolving 0.020 g of CaCO, in acid and diluting to 1.000 L. ⚫ After blanking the instrument, the three absorbance readings from the standard were 0.101, 0.096, and 0.104. Hint: Determine the slope of a 'two-point' calibration plot using the blank and average reading of the standard; use the standard deviation of the 3 absorbance readings as s ( )4 ppm ( )3 ppm ( ) 1 ppm ( ) 0.2 ppm
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.
An unknown sample of Mn2+ gave an absorbance of 0.392 in an atomic absorption analysis. Then 2.00 mL of solution containing 100.0 ppm of Mn2+ (=μg/mL) was mixed with 90.0 mL of unknown, and the mixture was diluted to 100.0 mL in a volumetric flask. The absorbance of the new solution was 0.600. The blank reading for this experiment is 0.010. Denoting the initial, unknown concentration as [Mn2+]i, write an expression for the final concentration, [Mn2+]f, after dilution. Units of the concentration are ppm. In a similar manner, write the final concentration of added standard Mn2+, designated as [S]f. Find [Mn2+]i in the unknown.
Following the experimental procedure, a student combined 5.00 mL of 0.0020 M Fe3+ and 1.00 mL of 0.0020 M SCN- with 4.00 mL of water to create their Trial 1 solution. The student used their spectrophotometer to measure the absorbance of the reaction mixture and recorded an absorbance of 0.095. a. The initial concentration of Fe3+: M (give to nearest 0.0001 M) b. The initial concentration of SCN-: M (give to nearest 0.0001 M) c. The equilibrium concentration of FeSCN2+: (give as decimal to nearest 0.000 001)Hint: The extinction coefficient of FeSCN2+ is 4,630 M-1*cm-1 and the cuvettes we use have a path length of 1.0 cm. d. The equilibrium concentration of Fe3+: M (give as decimal to nearest 0.000 001 M) e. The equilibrium concentration of SCN-: M (give as decimal to nearest 0.000 001 M) f. The equilibrium constant K: (give to nearest tens place)
6. A sample of an alum was analysed by atomic spectroscopy and gravimetrically to determine its structure. A 0.1000 g of the sample when treated with BaCl₂ produced 0.0984 g of a white solid after drying to constant weight. Another 0.1000 g sample of the alum when heated at 105°C for several hours produced a weight loss of 0.04558 g while the % of K in the sample was determined by atomic spectroscopy to be 8.240%. Use these results to work out a formula for the alum. [M,/ g mole¹: K 39.10; Al 26.98; BaSO, 233.39; SO² 96.06; H₂O 18.0148]
A 4.48 mg sample of a compound has a molar mass of 158.03 g/mol was dissolved in a 1000 mL volumetric flask. A 1.00 mL aliquot was withdrawn, placed in a 10.00 mL volumetric flask, and diluted to the mark. A 10.00 mL aliquot was placed in a 1.00 cm cell and percent transmittance of 30.9% at 520 nm. Calculate the molar absorptivity of KMnO4, at 520 nm
An absorbing solution transmits just 38 of every 140 photons to the detector. If the cell width was 2.0 cm and the analyte concentration was 26 mg/L, what was the analyte absorptivity (ppm-1 cm-1)?
What is the purpose of reference beam in the double-beam spectrophotometer shown in Figure 20-1? Select all the correct answers. a)To correct for changes in source light intensity as a function of time b)to correct for changes in intensity of the light source as a function of wavelength c)to correct of scattering of light off the surface of the sample cuvette d)to correct for absorbance of the solvent e)to correct for changes in detector signal as a function of wavelength
A green solution containing Ni+2 ions absorbs 580 nm light. Undiluted, a sample of this solution sampled in a 1.00 cm diameter cuvette has an absorbance of 0.9765 a.u.. If the molar absorptivity coefficient for Ni+2 is 6.3 x 104 M -1 cm -1 at 580 nm, how much of the original stock Ni+2 solution (in mL) needs to be added to water to create a total dilute solution volume of 10.00 mL that measures an absorbance of 0.146 a.u. at 580 nm? Report your answer to 3 significant figures. Do not include the "mL' unit label in your response