Scott test is one of the methods used for screening for Cocaine in Forensic Chemistry. The multi step method consists of a) reacting the sample drug with cobaltous thiocyanate b) dissolving of the formed precipitate by adding HCl and c) extraction of coordination compound with Chloroform d) measurement of absorbance of extracted coordination compound at 627 nm What reaction occurs when HCl is added to dissolve the precipitate ? a.Lewis acid- Lewis base reaction b.Lewis acid- Bronsted Lowry base reaction c.Bronsted Lowry acid – Bronsted Lowry base reaction d.Arrhenius acid – Arrhenius base reaction

Scott test is one of the methods used for screening for Cocaine in Forensic Chemistry. The multi step method consists of a) reacting the sample drug with cobaltous thiocyanate b) dissolving of the formed precipitate by adding HCl and c) extraction of coordination compound with Chloroform d) measurement of absorbance of extracted coordination compound at 627 nm What reaction occurs when HCl is added to dissolve the precipitate ? a.Lewis acid- Lewis base reaction b.Lewis acid- Bronsted Lowry base reaction c.Bronsted Lowry acid – Bronsted Lowry base reaction d.Arrhenius acid – Arrhenius base reaction

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter12: Spectrochemical Methods

Section: Chapter Questions

Problem 16P

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Scott test is one of the methods used for screening for Cocaine in Forensic Chemistry. The multi step method consists of a) reacting the sample drug with cobaltous thiocyanate b) dissolving of the formed precipitate by adding HCl and c) extraction of coordination compound with Chloroform d) measurement of absorbance of extracted coordination compound at 627 nm All the reactions in this multistep method are not fully understood. However, it was determined that there are 2 moles of cocaine in coordination compound measured in last step. If coordination compound is represented as “Scott” coordination compound, which of the following is correct “stoichiometric” factor to get mass of cocaine from mass of measured complex ? a.g (Scott coordination cpd) * MM (Scott coordination cpd) MM (cocaine) b.g (Scott coordination cpd) * 2 *MM (Scott coordination cpd) MM…
Scott test is one of the methods used for screening for Cocaine in Forensic Chemistry. The multi step method consists of a) reacting the sample drug with cobaltous thiocyanate b) dissolving of the formed precipitate by adding HCl and c) extraction of coordination compound with Chloroform d) measurement of absorbance of extracted coordination compound at 627 nm. Which molar absorptivity will you use to calculate concentration of cocaine ? a.cocaine molar absorptivity b.cocaine -cobaltous thiocyanate complex molar absorptivity. c.HCl - cobaltous thiocyanate molar absorptivity d.cobaltous thiocyanate molar absorptivity
The red color of soil is often due to the presence of iron. Metal ions are extracted from soil by stirring the soil in acid and then filtering the solution. One method for the analysis of Fe2+ is to form the highly colored Fe2+–thioglycolic acid complex. The complex absorbs strongly at 535 nm. Calibration standards of 1.00, 2.00, 3.00, 4.00, and 5.00 ppm are prepared by transferring appropriate amounts of a 10.0 ppm working solution of Fe2+ into separate 50-mL volumetric flasks, each of which contains 5 mL of thioglycolic acid, 2 mL of 20% w/v ammonium citrate, and 5 mL of 0.22 M NH3. After diluting to volume and mixing, the absorbances of the standards are measured. a)What is the effect on the reported concentration of iron in the sample if there is a trace impurity of Fe2+in the ammonium citrate?
The red color of soil is often due to the presence of iron. Metal ions are extracted from soil by stirring the soil in acid and then filtering the solution. One method for the analysis of Fe2+ is to form the highly colored Fe2+–thioglycolic acid complex. The complex absorbs strongly at 535 nm. Calibration standards of 1.00, 2.00, 3.00, 4.00, and 5.00 ppm are prepared by transferring appropriate amounts of a 10.0 ppm working solution of Fe2+ into separate 50-mL volumetric flasks, each of which contains 5 mL of thioglycolic acid, 2 mL of 20% w/v ammonium citrate, and 5 mL of 0.22 M NH3. After diluting to volume and mixing, the absorbances of the standards are measured. a)Use the data table below to prepare a calibration curve (absorbance versus concentration in ppm). Fit the data to straight line and find the equation for the straight line and the R2 value. (Hint: Think about what to do with the absorbance of the blank.)
Spectroscopy and a Calibration Curve Prepare a series of standard solutions of the colored compound with known concentrations by diluting the stock solution with distilled water. Use volumetric flasks to ensure accurate dilutions. Let's assume we have a stock solution of potassium permanganate (KMnO4) with a concentration of 0.100 M (molar). We will prepare five standard solutions with the following concentrations by diluting the stock solution with distilled water: 0.020 M 0.040 M 0.060 M 0.080 M 0.100 M Measure the absorbance of each standard solution at the wavelength of maximum absorbance (λmax) using the UV-Vis spectrophotometer. Record the absorbance values. For 0.020 M: Absorbance = 0.150 For 0.040 M: Absorbance = 0.290 For 0.060 M: Absorbance = 0.440 For 0.080 M: Absorbance = 0.580 For 0.100 M: Absorbance = 0.730 Plot a calibration curve by graphing the absorbance values (y-axis) against the corresponding concentrations (x-axis) of the standard solutions. Use a linear…
The absorbance values observed during the determination of the complex stoichiometry with the Job method using the spectroscopic method were plotted and the following correct equations were obtained. What is the n value of the compound formed by Fe + 3 and SCN- ions? 1. Line equation: y = 2.6188x + 0.1608 2. Line equation: y = -2.5963x + 2.7203 a) 1 b) 3 c) 0.5 d) 2 e) 5
The absorbance values observed during the determination of the complex stoichiometry with the Job method using the spectroscopic method were plotted and the following correct equations were obtained. According to this, what is the n value of the compound formed by Fe + 3 and SCN- ions?1. Line equation: y = 2.6188x + 0.1608 2. Line equation: y = -2.5963x + 2.7203
The absorptivity data for the complexes formed when metal ions A and B react with 2,3-quinoxaline-dithiol at the wavelength of 512 and 656 nm are given in the table below: A 0.350 g of soil sample containing A and B metal ions was dissolved in dilute acid and subsequently diluted to 50 mL with distilled water. A 25 mL aliquot was treated to eliminate interferences, after the addition of 2,3-quinoxaline-dithiol, the volume was adjusted to 50 mL. This solution has an absorbance of 0.514 at 510 nm and 0.357 at 656 nm in a 1-cm cell. Calculate the respective percentage of the metal ions A and B.
The absorbance values observed during the determination of the complex stoichiometry with the Job method using the spectroscopic method were plotted and the following correct equations were obtained. What is the n value of the compound formed by Fe + 3 and SCN- ions? 1. Line equation: y = 2.6188x + 0.16082. Line equation: y = -2.5963x + 2.7203
Flame Atomic Absorption Spectroscopy (FAAS) method is selected due to its wide applicability for metal ion analysis in drinking water samples. Title: Determine the concentration of selected heavy metals (Cu and Cr) in the unknown tap water sample. Question: Discuss.
The absorbance of a 0.1 M solution of a complex was 0.15 at max. What is the value of molar absorptivity for this complex? What is the geometry of this complex?
What is meant by transmittance and absorbance and which term is more preferable when doing expermines such as determining the formula of a complex ion using colorimetric method. please don't reject the question :'( I really need to know :'( :'(