EXPERIMENT #7: Spectroscopic Analysis of a Dye General Chemistry Laboratory,

| September 12, 2019

EXPERIMENT #7: Spectroscopic Analysis of a Dye General Chemistry Laboratory, Spencer Hall 207 Morgan State University, Baltimore, MD April 31, 2019. 8:00 a.m. – 10:50 a.m Title: Spectroscopic Analysis of a Dye Abstract:MAIN GOAL/PURPOSE, HYPOTHESIS, KEY QUESTION, RESULTS, CONCLUSION. This lab dealt with the absorbance a of a new cyanine dye developed and used in things such as labeling proteins and nucleic acids in biomedical imaging that has a lot of applications in drug development.The purpose of this experiment is to understand how light interacts with a dye solution and to use this knowledge to determine the amount of dye in an unknown. This experiment is based on assumptions that there is a correlation between absorbance and the concentration of dye in the solution. The hypothesis is that as the concentration the dye increases the absorbance the dye also increases. For the experiment, a stock solution using a given mass of the cyanine was made, along with 5 different standard solutions using the made stock solution the controls involved in the experiment are spectrophotometer used, the stock solution used, and the concentration of the dye used. The experiment could not be completed due to errors occurring when trying to measure the absorbance of the standard solutions. Introduction:DISCUSS THE MAIN GOAL AND PURPOSE , KEY CONCEPTS OR THEORIES The objective of this laboratory exercise is to become familiar with a typical spectrophotometric analysis and to examine the effect of an interfering substance. This lab was the calculation of the concentration of the dye solution; and using the prepared series of standard solutions, made from a stock solution, to measure absorbance with a spectrophotometer. The spectrophotometer is a vital machine for researchers, scientists, and biological and chemical engineers in studying various substances. Understanding the function and output results of spectrophotometry can be essential for future studies involving light absorbance of a wavelength and the concentration of a sample. This lab discusses the important relationship between material concentration and the intensity of light over a function of wavelength. A spectrophotometer is defined as an instrument used to measure the intensity of wavelengths in a spectrum of light, and commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gasesThe key concepts in this experiment are Absorbance, beer’s law, absorptivity, path length and Calibration curves. Absorbance is a measure of the capacity of a substance to absorb light of a specified wavelength. It is equal to the logarithm of the reciprocal of the transmittance. Absorptivity is a measurement of how strongly a chemical species absorbs light at a given wavelength. Path length is considered to be the overall length of the path followed by a light ray or sound wave. Calibration Curve is a method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. Beer Law is a physical law that states the quantity of light absorbed by a substance dissolved in a non absorbent solvent is directly proportional to the concentration of the substance and the path length of the light through the solution and Absorptivity which is a measurement of how strongly a chemical species absorbs light at a given wavelength.. The key question/purpose of this experiment is determined whether the absorbance of the dye in influenced by the concentration of the dye in the solution. It is important to know that transmittance because it is presented as a percentage and absorbance is unitless. And it is important to use the Beer-Lambert law because it is represented as an equation that shows the relationship between the absorbance and transmittance. The equation represents the molar absorptivity, the concentration of the compound inside the solution, and the length of the light that is passed through the sample. These equations are used to calculate the data in this experiment to get the final results. Experimental Details Objective -To establish how to relate the abstract of a solution containing the dye concentration in the solution. -To determine the concentration of the dye in an unknown solution using the concentration. Materials -250mL beaker -25mL cleaning solution -50mL beaker (For cleaning solution) -Spectrophotometer -Distilled water -Sample stock solution -Test tube -solvent-ethanol Procedures: -Fill a 50mL beaker with 25mL cleaning solution -Clean all Apparatus/materials using solution, distilled water and cleaning brush. -Dry all materials with paper towels. Experiment : During this experiment David and I understood the three main procedures that were needed to calculate all data. First, David and I expected to perform all calculations which helped determine the absorbance of the solvent ethanol solution. David and I then used the spectronic spectrophotometer to help determine the concentration of the unknown substance by using all recorded information. Before David and I begin the lab experiment we begin calculating the given data to find the number of moles and molarity of for concentration. After, David and I allowed the instrument to warm up for 10 minutes while setting the percent transmittance (%T) to zero. Next, we gathered 100 mL of the ethanol. After gathering the solution we then filled the dye (5.4g of dye with the ethanol solution transfering into a volumetric flask repeating until all the dye had dissolved. David and I then filled each clean with no air bubbles or fingerprints test tube with ethanol solution and inputted into spectroscopic till the data reach 100. Following the steps David and I then calculated the VI value for number 1-5. After David and I tested each test tube in three trials. David and I then added the NOT NULL to a clean test tube and tested in three trials recording (0.696, 0.694 AND 0.692). Results and Calculations: For David and I record, we put all the absorbance reading in a chart below. Our information we calculated into excel. This chart David and I considered to be important as it displays the final results of our experiment. Other data David and I recorded was the final results were we calculated the dilution of each solution for the number of moles and molarity. H COUNT 40 (1.008 X 40) = 40.32 C COUNT 34 (12.011 X 34) =408.34 I COUNT 1 (126.904 X 1)= 126.904 CI COUNT 1 (33.5 X 1) =35.5 N COUNT 2 (14.01 X 2) =28 = 639.06 g/mol Concentration Absorbance 2.96 0.915 0.885 0.855 5.92 1.270 1.270 1.270 8.87 1.470 1.460 1.440 11.85 1.400 1.400 1.420 14.79 1.600 1.560 1.580 NOT NULL TRIAL #1 0.696 X= Concentration Y= Absorbance TRIAL #2 1.694 TRIAL #2 0.692 1.[11.85 +1.407] 2. [1.580 +14.29] Formula: Y=MX + B Y2-Y1 X2-X1 1.580 – 1.407 14.79 – 11.85 = 0.173 2.94 M=0.054 (Slope) 1.580 = 1.159 (14.79) + B 0.059 X 14.79 =0.87 =1.580 / 0.8 =1.816 = B UNKNOWN: c =a/eb c=? a= 0.694 (Absorbance) eb= 0.059 (Slope) ?=0.694 0.059 = 11.76 = Unknown concentration 1 graph line graph Discussion: DISCUSS RESULTS OBTAINED Conclusion: DISCUSS THE MAIN GOAL/PURPOSE , MAJOR RESULTS OBTAINED . References: General Chemistry Laboratory Manual, An integrated Critical Thinking Approach, By Angela J Winstead, Morgan State University, McGraw Hill 2013. …
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