Project 2 Worksheet - The TA\'s name was Wenmo Sun. This was for the lab portion of the class. PDF

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The TA's name was Wenmo Sun. This was for the lab portion of the class....

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Your TA’s name: __________Wenmo__________

Your name: _____Dana

Woods______ Lab section: ________________001I_________

Group members: Daniel, John,

Joan

PROJECT 2 REPORT _______________________________________ _____________________ __________________ _______________________________________

All sections must have a line spacing of 1.5 to give room for LTA feedback (the document is set to this spacing) Central Goals: State the overall project goal and the central goal of each project session explaining the relevance and importance of achieving the stated goals. Write in complete, well composed sentences. There is a four sentence limit. The overall goal of the experiment is to determine and learn how to complete different methods for separating substances the to use that data to identify and quantify those substances. For session one, the central goal is to separate several food dyes then use the Rf values to determine the identities of two unknown dies, and by achieving this, it will confirm which solvent is the most effective at separating different dyes. For session two, the central goal is to isolate the food dyes in different types of candies using forms of filtration, centrifugation, and evaporation, and by achieving this, it will determine the identities of the dyes present in candies. For session three, the central goal is to identify the absorbance versus concentration graph for a specific dye using absorbance spectroscopy, and by achieving this, the amount of dye in a candy containing the same dye can be quantified.

Claims: In paragraph form state your core findings (major claims) in a clear and concise manner using carefully composed, complete sentences. You are limited to no more than five sentences. In session one, the best paper chromatography mobile phase was found to be a 75% 5M NaCl and 25% water mixture. In session two, the best preparation to isolate food dyes from candy was found to be 1) centrifugation, 2) gravity filtration (with both a filter

pipette and a paper filter), 3) syringe filtration, and 4) solvent evaporation. Using the above order of steps, it was determined that the dye present in my candy was blue 1. In session three, the relationship between the absorbance and concentration for my dye was determined. That relationship was A = 1.214x10^5c + 0.02563 (where A is absorbance and c is concentration), and this formula was used to determine the concentration and amount of my dye in a candy with the same dye present.

Evidence and Analysis: Clearly describe how the data that you collected and the calculations that you completed support your major claims. You are expected to build convincing arguments to justify your claims using relevant data. This section should be written in narrative form, using data and calculations as needed to justify your main claims. Use tables and graphs to organize and present data that clearly supports your argument. You have a three page limit. For session one, many different combinations of solvents were tested before we found one that worked best for us. We tried 100% water, 100% ethanol, 100% sodium chloride, 50% water 50% ethanol, 75% sodium chloride 25% water, 50% water 50% sodium chloride, 75% water 25% sodium chloride, and 60% water 40% sodium chloride. It was determined that the 75% sodium chloride 25% water mixture was the best mobile phase composition for our dyes. The Rf values for each dye were determined. We then ran two unknown dyes through chromatography with the same mobile phase to determine their identities. It was found, using the Rf values, that unknown A contained Red 3 and Green 3 and unknown B contained Yellow 6 and Blue 1. This was determined because the Rf values of the dyes in the unknowns were the same as the Rf values calculated in the known dyes.

For session two, we were given a list of ways to separate and filter the dye out of a candy. Our task was to determine the best order in which these techniques would be used to get the dye out of the candy. Our group used the following steps to get the dyes out of our candies: dissolving in water, centrifugation, paper filtration, filter pipetting, syringe filtration, evaporation, chromatography. The candy I chose was a blue gum ball, so I followed the above procedure with that. After centrifugation, I compared the Rf value of my dye with the Rf values from the lab in session one. In this way, it was determined that my dye contained Blue 1. The Rf value of the dye in my blue gum ball was 0.81 (4.4/5.4) and the Rf value of Blue 1 is 0.82 (it is difficult to see in the picture).

In session three, our goal was to find the relationship between absorbance and concentration for a specific dye then use that to determine the amount of grams of dye per gram of a certain candy with that dye in it. The first thing we had to do was dilute a stock of a dye in order to get the relationship. I chose Green 3. We did a linear dilution, so the graph would be linear. The optimum absorbance for my dye was found to be at 626 nm, so this was the absorbance used to calculate the concentrations of my dilutions. The equation I got for absorbance versus concentration was A = 1.214x10^5c + 0.02563, where A is absorbance and c is concentration. The 0.02563 can be dropped off since it is negligible. We are now left with the Beer’s law equation. The next step in this session was to quantify the amount of Green 3 dye in a candy that contained Green 3 dye. I had to guess which candy it was, and I ended up choosing a blue candy, since blue is made up of yellow and green. To verify that my blue candy contained Green 3 dye, the same procedures that were used in session two were utilized again. I got the dye by itself then ran it through the spectrometer. The wavelength peak was at 630 nm, which is close to the 626 nm of the Green 3 stock, so it was determined that my candy did contain Green 3 dye. The absorbance at that wavelength was 0.522. That absorbance can be put into the equation (0.522 = 1.214x10^5c) and concentration can be solved for. The concentration was found to be 4.30x10^-6. This is divided by 25L, which was the amount of dye used, to get 1.72x10^-7 mol/L. Moles is then converted to grams using the molar mass of the Green 3 dye (808.85 g/mol). This gives us 1.39x10^-4 grams. This means that there are 1.39x10^-4 grams of Green 3 dye per one gram of the blue candy.

Final Reflections: Using a narrative style, summarize the following: a) to what extent you meet the central goals of the project; b) the main things you accomplished; c) what else would need to be done to fully meet the goals. You have a four sentence limit. I believe our group met the central goals of the project to the best of our abilities, following the procedures and project guides as well as we could. The main tasks my group accomplished were finding the best mobile phase composition for our given dyes, identifying unknown dyes (using chromatography), coming up with the steps that need to be taken in order to get a dye out of a candy then identifying it (using chromatography), and quantifying the dyes in certain candies using mass spectroscopy and the absorbance versus concentration graph for that substance. Of course there were errors, just like during any lab project. Some things that could be fixed to better meet the goals would be to make sure we have as much of the sample as possible after purifying the dye, making sure the dye is all that is left after all the filtrations, and ensuring the calculations are made correctly using the absorbance versus concentration equation....