Identifying Unknown Red Solutions using Absorption Spectrums and Smell
CHEM 112-Section: 002
Due Date: October 17th, 2018
Keanu Young
Proposal Abstract:
A set of experiments will be outlined in this proposal that one may perform on the three unknown red solutions presented in lab. This proposal seeks to analyze absorption spectrums of the three unknown red solutions to see if they contain the same molecule(s). The second proposed experiment seeks to identify the smell classification of the three unknown red solutions to compare them to known solutions. At the end of these experiments, the data collected will be absorbance spectrums and a smell classification that will lead us to some answers and further experiments. The end goal is to determine the identity of the three unknown red solutions using a set of different experiments. Below is a set of scientific questions aimed at finding the identity of the unknown solutions.
Scientific Questions:
How can one use an absorbance experiment to measure the amount of red molecules in the different vials? How can one identify the three unknown red solutions using smell? How will the lambda max differ across the three unknown red solutions? How does the molecule count in each of the three unknown red solutions contribute to their absorption spectrum? How can one use analytical methods to determine if the three unknown red solutions contain the same molecules?
Experimental Methods:
Experiment #1:
To determine the analytes in the three unknown red solutions, we can perform an experiment using analytical methods. In this experiment, LoggerPro software connected to a spectrophotometer, cuvettes, kimwipes, three 50 mL beakers, five and 10 mL volumetric pipets, 10 mL of each unknown red solution, and distilled water will be used.
Experiment #1
Procedure: Fill a clean cuvette approximately two-thirds full with deionized water to create a control sample. Before placing the cuvette into the spectrophotometer, use a kimwipe to eliminate fingerprints. Make sure to use a kimwipe before placing a cuvette into the spectrophotometer throughout the procedure. Insert the blank sample into the spectrophotometer and use the menu on LoggerPro to select ‘Experiment > Calibrate > Spectrometer I.’ Click the ‘Finish Calibration’ button and wait for it to complete. In the upper left corner, the absorbance value should read at or near zero. If not, repeat the steps above until it does. Start out by measuring out 10 mL of each red unknown solution into separate 50 mL beakers and label them. Using the 5 mL volumetric pipette, fill two separate cuvettes of each red solution until they are two-thirds full. The total amount of cuvettes should be six. On the LoggerPro menu, select ‘Data > Data Browser.’ Insert one of the six solutions into the spectrophotometer and then click the ‘Collect’ button. Give it a few seconds to stabilize and then click ‘Stop. ‘On the LoggerPro menu select ‘Experiment > Store Latest Run.’ Rename the run to remember the sample. Swap out of the cuvette with the other dye samples and repeat the steps above. Do this until data for all six cuvettes are collected. For the data sets for each sample, compare the lambda max and average them to make sure the data is accurate. Please note if they are not accurate, start over and collect data again if needed. Print out the absorption spectrum and label the data correctly. Record the data found in the absorbance spectrums and compare the lambda max, the peak width, and the absorbance. If these observations are similar across the three red solutions, then the chemical makeup is most likely similar as well.
Experiment #2:
Smelling known substances and comparing them to the three unknown red solutions can help us determine their identification. In this experiment, you will start off by smelling red known substances from the stock room, and then the three unknown red solutions. At the end, one will determine which known substance smells the most similar to each of the three unknown red solutions. Classify the smell of each substance from one of the five categories: minty, fishy, sweet, putrid, and camphor.
Experiment #2 Procedure: Obtain vials A-E, which will all be different red solutions from the chemistry stockroom. As a lab group, determine the smell classification of each solution using the classifications mentioned above. The smell classification cannot be identified as two different categories, only one. Also, the lab group must come to an agreement on the smell classification of each substance. Record the smell classification in your lab notebook using a table. The table should have the following headings:
Vial
Chemical Name
Smell Classification
Molecular Formula
Structural Formula
The TA will provide the class with the chemical names and formulas for vials A-E. Record this data in your master table in your lab notebook. Compare the chemical name and formulas to the smell classification and come up with patterns within the data. Record any patterns you notice as a group in your lab notebook. Identifying these patterns in molecular formulas and structural formulas to a smell classification can help us determine the identity of the three unknown red solutions because knowing the smell can help predict the molecular and structural formula.
The next part of the experiment you will be smelling vials F-H, which are the three unknown red solutions. Identify the smell classification as a group once again, and make sure everyone comes to an agreement. Record these observations in the large table. Please note that you will not have the chemical name, structural formula, or molecular formula for vials F-H because the solutions are unknown. Go back and smell vials A-E again and pick a vial that smells the most similar to each of the three red unknown solutions. Record this data in the smell classification of the table, and state that it is the most similar vial. If none of the known solutions smell really similar to the three unknown red solutions, further experiments will need to be done in smelling other known red solutions.
Discussion:
If the amount of red molecules in the different vials is known, it is one step closer to identifying the solution because it can be compared to other solutions that have a known amount of molecules. The lambda max found on the absorbance spectrum will provide the absorbance of the solution, which can be compared to known solutions to help determine the identity of the unknown solutions. An absorbance spectrum that is identified as Beer’s Law will determine if the three unknown red solutions contain the same molecules.
Experiment #1:
The purpose for the first procedure is to collect the absorbance of each unknown red solution. To read an absorption spectrum, three pieces of data must be considered, which are the absorbance value, peak width, and lambda max. A similar lambda max can help determine if solutions are similar, because substances with similar lambda maxes have a similar chemical makeup. If the absorption spectrums of the three unknown red solutions all have the same lambda max, we will know that each of the solutions contain the same molecule(s). The absorption spectrums of the three unknown red solutions can also determine if the solutions contain different molecules, which would mean the lambda max would be different across the unknown solutions. We can also determine if the three unknown red solutions contain more than one molecule based off the absorption spectrum because there would be two or more peaks.
Experiment 2:
The purpose of this second experiment is to determine the smell classification of each unknown red solution. This is an easy method that is used to determine unknown substances. The smell classification may not clearly identify the solution but it can help predict a part of the identity of each unknown red solution. This experiment can lead to more experiments because if there is not a known solution that smells really similar or the exact same, then more known red solutions will need to be smelled.
The patterns that may be found across the different substances can provide us an insight in predicting the molecular formula, structural formula, and the chemical name of the three unknown red solutions. When looking at The Chemistry of Smell lab, in Activity II, I was asked to identify patterns in the data. The patterns that the class came up with are the following: Nitrogen contributes to a putrid smell; A carbon to hydrogen ratio of 1:2 contributes to a sweet smell; A carbon to hydrogen ratio of less than 1:2 ratio contributes to a minty smell; Two oxygens contribute to a sweet smell and one oxygen contributes to a minty smell; The prefix“amyl” contributes to a sweet smell. This being said, if a smell classification of sweet is assigned to one of the three unknown red solutions, there is a possibility that there is a 1:2 ratio of carbon to hydrogen in their molecular formula, two oxygens in their molecular formula, the prefix of“amyl” in its chemical name, or the suffix of “ate” in their chemical name. This information can narrow down the known substances that we decide to smell in further experiments to help find the actual identities of the three unknown red solutions.
These patterns are accurate because in the table made in Experiment 2: The Chemistry of Smell, substances in vials C and D are classified as both sweet. Their chemical names are Amyl Propionate and Isoamyl Acetate which both have the suffix of “ate” and the prefix of “amyl” that follow the patterns identified above in smell classification. Their molecular formulas are C8H16O2 and C7H14O2. The patterns are clearly evident in the molecular formulas because both have a 1:2 ratio for carbon and hydrogen molecules, and they both contain two oxygen molecules. The takeaway is that the patterns are accurate and can be applied to most substances, which is why we can use this experimental method to help identify the unknown red solutions. It may not workout perfect on the first try which is why further experiments with different known substances may have to be done.
Acknowledgements:
My lab partners, Edwardo Gomez, Amanda, and Janessa, and my TA, Yusef Farah, were all consulted to discuss the possible experimental procedures and for insight on how these experiments may lead us to answers and further experiments.
References:
Reynolds, B. Chemistry 112 Lab Manual; Colorado State University, 2016; p. 16-23, 33-44, 45- 54. Print.
[1]: Morel, Y.; Ibanez, A.; Nguefack, C. Fig. 6. Theoretical two-photon absorption spectra of ABN and POM molecules; 2000. https://www.researchgate.net/figure/229406972_fig1_Fig-6- Theoretical-two-photon-absorption-spectra-of-ABN-and-POM-molecules (accessed Oct. 19, 2016).
[2]: N.p.a. Generating and Using a Calibration Graph; N.p.d. http://www.umich.edu/~chem125/softchalk/Exp2_Final_2/Exp2_Final_2_print.html (accessed Oct. 19, 2016).