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CHEM 237 Final Exam TAMU Everything (This QL includes every assignment from this class: sapling, discussion questions, the book, and important results from experiments) with Expert Verified Solutions $13.49   Add to cart

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CHEM 237 Final Exam TAMU Everything (This QL includes every assignment from this class: sapling, discussion questions, the book, and important results from experiments) with Expert Verified Solutions

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CHEM 237 Final Exam TAMU Everything (This QL includes every assignment from this class: sapling, discussion questions, the book, and important results from experiments) with Expert Verified Solutions

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  • October 22, 2024
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CHEM 237 Final Exam TAMU Everything (This
QL includes every assignment from this class:
sapling, discussion questions, the book, and
important results from experiments) with Expert
Verified Solutions




What region if the IR spectrum is best used for distinguishing between isomers that have the
same functional groups? - ✔✔1400-400 cm-1



The IR spectrum displays the wavelengths at which specific functional groups absorb
energy. Which wavelength do each of these bonds absorb energy?



1. C--C [alkene]

2. C--O [ester]

3. O-H [carboxylic acid] - ✔✔1. C--C: 1600 cm-1

2. C--O: 1800-1460 cm-1

3. O-H: 4000-3000 cm-1



The IR spectrum displays the wavelengths at which specific functional groups absorb
energy. Which wavelength do each of these bonds absorb energy?



1. C--C [Alkene]

2. N-H [amine]

3. C--O [ketone] - ✔✔1. C--C: 1600 cm-1

,2. N-H: 4000-3000 cm-1

3. C--O: 1800-1640 cm-1



The IR spectrum displays the wavelengths at which specific functional groups absorb
energy. Which wavelength do each of these bonds absorb energy?



1. O-H [alcohol]

2. C--O [aldehyde] - ✔✔1. 4000-3000 cm-1

2. 1800-1640 cm-1



Label each of the statements as true or false:



1. infrared spectra can detect impurities in a sample

2. infrared spectroscopy is nondestructive

3. IR is good for detecting and identifying functional groups in a sample

4. IR can be used to detect most any kind of sample - ✔✔1. T

2. T

3. T

4. F



IR is not good at detecting all mixtures



What type of samples is IR not the best at detecting? - ✔✔IR is not the best for detecting samples
with complex MIXTURES.



The spectrum would be overly complicated with the bond frequencies of all the different. complex
molecules in the MIXture.



Exp: who has my cmpd - ✔✔

,a preliminary investigation reveals that an unknown material has a melting point range around 150
Celsius.

[http://dam.saplinglearning.com/authkey/onB_C4P/preview/F6xfN72X4WcAPT3dq4zCOH/previews/ma
xWidth_1600_maxHeight_1600.jpg////ochem_graphB_1726114_preview.jpg?_=2]



what voltage mus the melting point apparatues be run at to produce a 2 C/min change near 150 C? -
✔✔45



How does a eutectic mixture affect the melting point? - ✔✔the composition of a mixture of
two compounds that generates the LOWEST possible melting point



are eutectic mixtures always in a 1:1 ratio?

can eutectic mixtures dissolve in one another? - ✔✔1. NO



2. usually



Why is it good to perform a mixed melting point determination at two different ratios of unknown to
know material in the melting point capillary? - ✔✔it is possible that one of the particular
combinations of these two compounds can generate a eutectic mixture



list 3 main ways to access the purity and identity of a substance - ✔✔melting point
determination, solubility tests, and thin-layer chromatography



which waste bin would each of these go to:



1. used mp capillaries

2. contaminated paper towels

3. Sodium bicarbonate solution

4. TLC solvent - ✔✔1. glass

2. solid waste

, 3. 10% aqueous waste

4. hexanes, ethyl acetate, etc.



Rules for TLC: [fill in the blank:]



1. in the beginning, the solvent level should be below (______)

2. do not allow (______) to touch the filter paper

3. allow the solvent to get with in (______)mm of the top of the plate - ✔✔1. the marked spots/origin

2. bottom of the filter paper

3. 5-10 mm



Rules for TLC: fill in the blank



1. when the solvent has reached the correct height, (______)

2. TLC date is interpreted in terms of (______)

2. do NOT allow the solvent to get within (______)mm of the top of the plate - ✔✔1. remove the
plate from the chamber and immediately draw a line at the solvent Front

2. Rf values

3. 1-2 mm



During a melting point determination, is it normal to first take a rapid rough measurement followed by
a slower more accurate measurement.



Why is it important to allow the Mel-temp to cool 15 C below the mp before placing the 2nd capillary
tube in, and to set the voltage to generate 1-2 C/min through the mp range? - ✔✔a rapid
temperature increase would give a melting point range that is much higher than the true value



how would the mp of an organic compound be affected if there were a shard of glass inside the
mp capillary? explain. - ✔✔the mp range would NOT be affected.

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