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Experimental Design and Methods in Chemistry

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

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

Laboratory Questions

A laboratory has four hoods each of which is 39 inches wide. When the hood door is open to a height of 8 inches and the hoods are operating, the average air velocity through the hood is 170ft/min. a. Evaluate the total ventilation rate for this room assuming that there are no other exhausts. b. The laboratory is designed for

Calculating Absorptivity

I have tried to play with all the numbers in this question, but nothing seems to be working. Nitrite ion, NO-2 is used as a preservative for bacon and other foods. It has been the center of controversy since it is potentially carcinogenic. Here is an abbreviated procedure for the determination: Step 1: 50.0 mL of unk

Identifying different solutions.

If I had 5 solutions that are not labeled (the solutions are ethanoic acid, calcium hydroxide, potassium bromide, sodium chloride and nitric acid) is there a way of identifying which one is which without using an indicator?