Answered: QUSTIONS AND PROBLEMS t 1. A student… | bartleby

Fundamentals Of Analytical Chemistry

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter7: Statistical Data Treatment And Evaluation

Section: Chapter Questions

Problem 7.21QAP

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QUSTIONS AND PROBLEMS t
1.
A student was trying to prepare acetaminophen in the laboratory. She found a
melting point range of 169 – 173°. The m.p. of acetaminophen is reported to be
168 – 172°C. How could the student have verified that the produce is
acetaminophen?
Suppose in part C you mixed your unknown with one of the three reference
and the mixture immediately melted. What would you conclude

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A 18 g of unknown organic sample was dissolve in 756 mL of benzene. The boiling point of benzene was increased by 3.36oC. As the first step of analysis, determine the moecular weight of the unknow sample? Kb of benzene= 2.64oC/m Bb of benzene = 80.09 oC density of benzene = 0.874 g/mL at 25 °C Answer in whole number, no units required.
I would need help with these questions. The method referenced above was followed by a student and she got the following results: Caffeine Std. Conc. (ppm) Absorbance 100 1.806 50 0.899 40 0.724 30 0.545 20 0.365 10 0.183 Further, she analyzed an unknown sample and she got the following results: Sample # Absorbance 1 0.398 1. Graphically find the concentration in ppm and then calculate in mol/L of Caffeine in Sample #1? 2. Which solvent was used to extract Caffeine and why? Why is it necessary to do extraction three times? 3. Cuvettes used in this experiment were made from which material and why? 4. At what wavelength the Absorbance was measured?
What is ΔSsys for a condensation phase transition at 26.5 °C for a compound that condenses at 26.5 °C and the ΔHsys = -40.1 kJ mol-1 for this process? Express your answer in J mol-1 K-1 to at least two significant figures.
The melting point (mp) range of reference compound A is 320-340°C. The mp range of a 1:1 mixture of a sample of A with a sample of unknown compound B is found to be 140-300°C. Do the samples consist of identical compounds? A)Yes, because the mp of the mixture is lower than the mp of pure A. B) Not enough information is given to answer the question C) Yes, because they melt over a broad range. D) No, because the mp of the mixture is lower than the melting point of pure A.
Please answer all 5 questions (it could be short answers). 5-1. What is the main barrier to separating liquid mixtures of less than 500 mL by distillation? 5-2. A sample mixture of ethyl benzoate (bp 212 Celsius) and dodecane (bp 216.2 Celsius) is injected on two GC columns. Column A has DC710 silicone oil as the stationary phase, and column B uses polyethylene glycol as the stationary phase. Which substance would be certain to elute first from column A and would the same material be expected to elute first from column B? Which column, A or B, would be expected to give the better separation of these two substances? 5-3. Question 5-2 refers to separating a mixture of two high boiling liquids by gas chromatography. These materials have similar boiling points. List several GC variables and conditions that would make it easier to separate thesesubstances by gas chromatography 5-4. Capillary GC columns have better resolution than packed columns even though the enormous surface area…
A student in New York City carried ou1t a boiling point determination for cyclohexane {b.p. 81• C) according to the procedure in this laboratory manual. Will this student's observed boiling point be the same as the value obtained by another student in Denver, Co'lorado.{Nicknamed the "Mile-High City" due to its high elevation)? Will it be lower or higher? Ex plain your conclusion.
10g coffee 4g sodium carbonate 40m dichloromethane 160ml distilled water coffee filter What are the principles behind caffeine being extracted from coffee using the above items? 1st sodium carbonate mixed with coffee then brought to a boil for 20min then solution/grinds are filtered. Then solution is added to a separatory funnel with 15ml of dichloromethane and two layers are observed so the bottom layer with DCM contains the caffeine, then this layer is collected in a beaker and dried out using molecular seeds. Then the solvent is brought to a boil with crude caffeine remaining and recystallized using 95% ethanol and brought to a boil again. Then the contents are vaccum filtered and allowed to dry resulting in 30mg caffeine.
I need help on figuring out which are the four data points that can be considered outliers, below is my graph following the intructions but, not I dont know which points are outliners.
5. In this experiment the height of liquid measured using the capillaryrise method (h in equation 14 below) is usually between 1 and 5cm. The capillary radius (r in equation 14 below) is usuallybetween 0.3 and 0.7 mm. Use this information and anapproximation to rewrite equation 14 in a much simpler form. Inthis version of equation 14, ρ has been replaced by d = density,do not use Greek letters or numbers. Equation 14: γ = 0.5(h+r/3)rdg ≈ 0.5[a]
19 g of unknown organic sample was dissolve in 640 mL of Dicloromethane (DCM). The boiling point of benzene was increased by 3.78oC. Determine the molecular weight of the unknown sample? Kb of DCM = 2.42oC/m Bb of benzene = 39.6 oC density of benzene = 1.33 g/mL at 25 °C Round your answer to the nearest whole number, no units required.
Enumerate and describe the signs of emulsion instability. At least 5-7
Which of the curves seems to have the shortest vertical line around its equivalence point? Explain why. (If you suspect that your data are inaccurate, explain which curve you think should have been most vertical and why.)

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