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Experimental Design and Methods in Chemistry

Analytical Chemistry with Vitamin B

22. A company produces vitamin B tablets tha claim to provide 100mg of riboflavin. A bottle is drawn from the stock, and one pill is determined to contain 100.9 mg(= +/-1.1mg) of riboflavin. A)How many samples are needed to confirm with 95% confidence that the pills contain at least 100 mg of riboflavin. B) How should

Analytical Chemistry - aqueous solutions

17. A certain material "X" has an ether/water partition coefficient, KD = 3.3. If 55 mL of 12 ppt aqueous solution is extracted with 6.0 mL of ether, how much X is drawn into the ether layer? 18. The amount of mercury in a freshwater stream is determined by flowing 500 m3 of water through a charcoal filter canister. The ch

Identifying Carbohydrates

An unknown carbohydrate could be reduced by a series of steps to a compound with five carbons. It does give a positive Benedicts test and it has two chiral carbons. What is the structure consistent with these facts?

Absorption Spectrum

The 12C16O absorbs in the infrared region of the spectrum at 2145 cm^-1. Calculate the position of the absorption of 13C16O.

NMR: Resonance Frequencies

See the attached file for the problem. 1. a) Calculate the resonance frequencies of the following nuclei, given the values for the nuclear magnetic moment and spin, at a field strength of 10 kG. B_N = 5.05 * 10^-24 ergG^-1. nucleus I u (in multiples of B_N) 11B 3/2 2.688 17O 5/2

Use of spectrophotometry to determine Ka

This involves the use of the equation; pH = pKa + log (activity coefficent of anion) + log (D -Dha)/(Da- - D), from the equation it is neccesary to plot pH against log(D - Dha)/(Da- -D). This appears to be the straight line eqn which can be solved (y = mx + c) for the function pKa + log (activity coefficient of anion

The Oxidation of Alcohol by Dichromate Ion

1) I'm given a spectrophotometer. How can I determine the rate law? I can only use the spectrophotometer to determine %T. How can I get from %T to concentration? What strategy do I have to use? Can you provide me a step by step strategy about how to get "from %T to concentration" and how to get "from concentration to rate law"?

Restaurant - Boiling Stones

I have a question that I found in a text book, can anyone help me answer it? It seems to be safe. Some of you are concerned with the fact that the operator of a Vietnamese restaurant used some stones as "boiling chips" in the pots where they cook food. Please provide a paragraph with rationale to support your argument/conc

Lab Experiment: How do I dissolve dirt?

Purpose: To introduce the student to a real world application of concepts learned so for in Analytical Chemistry. Apparatus: To be determined. Introduction: In this experiment you will be given a beaker containing dirt. Dissolve .25 grams using any method/chemicals/devices possible. You are NOT allowed to use hydrofluoric

95% Confidence Level and Systematic Error

We are using the book Analytical Chemistry 7th edition by Skoog, West, Holler, and Crouch This question requires all equations to be written out. Thanks so much! To test the quality of work of a commercial laboratory, 15 replicate analyses of a purified benzoic acid (68.8% C, 4.953%H) sample were requested. The absolute

Gas Chromatogram

Please refer to the attachments provided. When I did the gas chromatogram, I made a careless mistake, by not labeling the printout(A-D); A-C the 3 distillation fractions and D the undistilled residue. On the 1st printout w/ 4 peaks, I know that the highest peak is A and on the printout w/ two peaks I think the peak on the rt

Yellow Flame

When glass is heated, a yellow flame is observed around the point of heating. What does the yellow flame indicate? Why is it observed when glass is heated?

HPLC Column

An HPLC column of length 15cm and ID of 4.6mm is tightly packed with monodisperse ODS particles of diameter 3:m surface area 300m/g^2 and density 1.2g/mL. Dead volume is 1.2mL. Assuming that the particles are tightly packed and that the void volume is essentially due to the pore volumes of the particles, calculate: 1. the #

GC Problem

Calculate: 1. Corrected retention times for air and 3 alcohols 2. Specific retention volumes for 3 alcohols 3. Distribution constant for 3 alcohols 4. Capacity factor for 3 alcohols 5. The average number of theoretical plates and the average height of a theoretical plate for the column Given: 1. Column length: 1.1m ID

Chemical Separations Problem

The H (height equivalent of a theoretical plate) value for an HPLC column at mobile phase flow rates of 1ml/min, 3ml/min and 4ml/min are 4.1mm, 4.7mm and 5.675mm. Calculate: 1. The van Deemter parameters A, B and C 2. The flow rate at which H is a minimum and the value of H at this flow rate 3. The efficiency N if the length

Preparation of solutions

Hi-1st of all, would you please send back an email address so I may contact someone on the 3rd shift about something that was done on 3rd? Secondly, is there a way to request work to be done by a certain person if they are available? A couple of you last night were just wonderful!!!Olivia Problem: Describe how you would prepar

Chemical separation on a GC instrument

Given: 1. GC instrument 2. polysiloxane column 3. 1mM solution of each of the following compunds in methanol. Compounds divided into 3 separate groups: 1. Carboxylic Acid: a. benzoic acid b. Phthalic acid c. Toluic acid 2. Amino: a. aniline b. 4-aminotoluene c. ortho- pheylenediamine 3. Amino

Method Set-Up for a Chemical Separation

Suggest a buffer and mobile phase composition to get the best separation given: 1. HPLC instrument 2. C18 reverse phase column 3. 1mM solution of each of the following compounds in Methanol 4. Mobile phase is methanol-buffer mixture Compounds are 3 seperate groups: 1. Carboxylic Acids: a. Benzoic acid b

Capacity Factor Problem

Question: Two analytes A and B, have retention times of 13.5 min and 19.5 min, with peak widths of 2 min and 2.8 min for a mobile phase composition of 20% methanol and 80% H2O, on a 15 cm C18 column which has a dead time of 1.5 min. Determine the composition of methanol and H2O at which the capacity factor for A becomes 2. What

Analyte separation problem

The fraction of an analyte in the rth stage of a N stage separation if given by f(N,r)=(N!/r!(N-r)!p^r q^(N-r). Given: distribution ratios of 0.5 and 1.5 Stages 50 and 200 Phase volume ratio 0.3 What is the fraction of analyte in each stage and the stage number for analytes with the given dis

Capillary condensation in nanotubes

Is anyone familiar with a recent report where liquid water has been condensed inside a carbon nanotube and then imaged with an electron microscope at very low pressure (10^-5 torr)? Supposedly the water does not evaporate at this low a pressure. Is this truly possible and why? Does anyone have the reference for this experimen

Solvent-Solvent Extraction

Green Slime, an uncharged organic dye, is present in 600.0mL of water at an unknown concentration. The sample is extracted with 75.00mL of cyclohexane. After the extraction, the absorbance of the cyclohexane phase, measured at 635nm in a 1.00cm cell, is 0.870. The absorbance of a blank (pure cyclohexane) is 0.007. Using Beer's L

Absorption and fluorescence

An aromatic compound, RX, fluoresces at 470 nm (quantum yield = 0.1) after excitation at 340 nm. The molar absorptivity of RX at 340 nm is 1100. How much energy has been lost by non-radiative means or remains with the compound after it fluoresces at 470 nm? How many joules of energy per mole of 340 nm photons is retained by a 10

Absorption and Fluorescence

Question: An aromatic compound, RX, fluoresces at 470 nm (quantum yield = 0.1) after excitation at 340 nm. The molar absorptivity of RX at 340 nm is 1100. How much energy has been lost by non-radiative means or remains with the compound after it fluoresces at 470 nm? How many joules of energy per mole of 340 nm photons is retain

Determine Molar Absorptivity

A red-colored complex PbX4 prepared from Pb with ligand X() shows promise as a means to determine trace levels of lead in the environment. The analyst prepares five standard solutions (A, B, C, D, and E) of PB: 30, 60, 90, 120, and 150 ppm, respectively. 5 ml of each solution is mixed with 5 ml of 0.10 M X. The transmittance of


Methyl Orange is an acid-base indicator. In dilute solution, at a pH greater than 4.4, it is yellow. At pH=3.2, the solution appears red. Draw a structure of the species that is formed at the lower pH of the acid proton that adds to the azo nitrogen atom adjacent to the aromatic ring containing the -SO3 group. Why does the proto