2023_04_09_notebook_17066

pdf

School

University of California, Irvine *

*We aren’t endorsed by this school

Course

51LC

Subject

Chemistry

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by BaronSealMaster212

Chem 51LC S23 - Alex Lei Exp 0: Technique Review/PreLab/InLab PDF Version generated by Alex Lei on Apr 08, 2023 @09:44 PM PDT Table of Contents PreLab/InLab .......................................................................................................................................................................................................................................................... 2

PreLab/InLab Renee Link - Sep 21, 2022, 11:35 AM PDT Assignment #1 - Lab Period 1 ELN Before you can submit, access this assignment from Canvas. Pre-Lab Instructions 1. Complete the following items. Some may have been completed for you already. Detailed objective written in your own words. GHS Table for compounds used in lab. Equipment table with images. Use the Lab Equipment Images provided (see navigation bar on left side). Waste table including specific locations of where each waste item will be disposed of. Include images from the Lab Equipment Images provided. Procedure written in your own words. Make a flowchart for the extraction . In-Lab Instructions 1. Complete the Jamboard activity with your lab partner. 2. Continue filling in your notebook page. 3. Complete the red questions section. 4. Complete the experiment summary. 5. Click Submit in the yellow assignment box at the top of the page. This will automatically submit your assignment in Canvas and lock this page. James Harrison Griffin - Sep 23, 2022, 10:39 AM PDT Objective Renee Link - Mar 26, 2022, 12:17 PM PDT This experiment aims to review the lab techniques used in the previous experiments, which were essential to Chemistry 51LB. The skills for the first Technique Review lab will include Extraction, TLC, Recrystallization, Melting Range, and Mixed Melting Point. Liquid-liquid extraction, Recrystallization, TLC, and Melting Range (optional) will be tested individually and with people from selective groups to determine a concrete understanding of the basic concepts necessary to be successful in Chemistry 51LC. Toward the end of this lab section, we hope to be informed about our weaknesses and strengths in the lab techniques tested so that each individual may be caught up and well-informed on what must be done to succeed with later experiments. Alex Lei - Apr 04, 2023, 10:36 AM PDT Exp 0: Technique Review/PreLab/InLab 2 of 16

GHS Table Renee Link - Mar 26, 2022, 12:17 PM PDT Most of the GHS table has been completed for you. Fill in the missing rows as part of your pre-lab work. To edit the table: Hover your cursor over the table entry and choose the edit option (pencil icon). Click on the row you want to edit. Click on the edit button the row of options above the table. Add the necessary information in the pop-up window. Save your edits to the row by clicking the Save button in the pop-up window. Edit any additional rows. Save the edits to the table by clicking the save to page button. Renee Link - Mar 26, 2022, 12:17 PM PDT Show 10 entries Search: Showing 1 to 10 of 10 entries Acetone Danger Flammable Highly flammable liq… Keep away from spa… Keep container tightl… Irritant biphenyl Warning Irritant Causes skin/eye irrit… Wear PPE and thoro… Avoid breathing in an… Environm dichloromethane Warning Corrosisve Can cause drowsine… Avoid breathing in an… Use only in well venti… Irritant ethanol Danger Flammable Highly flammable liq… Use in well ventilated… Avoid sources of hea… Irritant Ethyl Acetate Danger Flammable Highly flammable liq… Keep away from spa… Use only non-sparkin… Irritant Hexanes Danger Flammable Highly flammable liq… Use in well ventilated… Keep away from hea… Corrosive methyl orange Danger Toxic Toxic if swallowed Do not consume duri… Wear proper PPE ge… naphthalene Warning Flammable Flammable solid. Keep in well ventilate… Avoid areas of heat s… Corrosive Sodium Sulfate Not hazardous Water Not hazardous View Copy to Clipboard Export to CSV Show / hide columns Chemical Name Signal Word GHS Symbol 1 Hazard 1 Hazard # 1 Minimize Risk 1a Minimize Risk 1b GHS Sy First Previous 1 Next Last Alex Lei - Apr 05, 2023, 10:56 PM PDT Exp 0: Technique Review/PreLab/InLab 3 of 16

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Equipment Table Renee Link - Mar 26, 2022, 12:17 PM PDT Erlenmeyer flask Graduated cylinder Plastic Pipette Scintillation Vial Hot Plate Renee Link - Mar 26, 2022, 12:25 PM PDT Exp 0: Technique Review/PreLab/InLab 4 of 16

Spatula Separatory funnel Clamp Weighing Paper TLC Chamber Exp 0: Technique Review/PreLab/InLab 5 of 16

TLC Plates TLC spotters UV lamp and visualization set-up Exp 0: Technique Review/PreLab/InLab 6 of 16

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Filter paper Exp 0: Technique Review/PreLab/InLab 7 of 16

Waste Table Renee Link - Mar 26, 2022, 12:17 PM PDT Waste Container Type of Waste Solid Waste: Naphthalene Leftover chemical solids. Liquid Waste: Leftover chemical fluids. TLC Waste: -Used TLC Plates Glass Waste: -TLC spotters -Any broken glass Alex Lei - Apr 04, 2023, 11:08 AM PDT Exp 0: Technique Review/PreLab/InLab 8 of 16

Exp 0: Technique Review/PreLab/InLab 9 of 16

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Alex Lei - Apr 06, 2023, 8:32 AM PDT Exp 0: Technique Review/PreLab/InLab 10 of 16

Exp 0: Technique Review/PreLab/InLab 11 of 16

Procedure Renee Link - Mar 26, 2022, 12:17 PM PDT The procedure, running account, and observations table have been started for you. Complete the procedure column before lab as part of your pre- lab work. Fill in the rest of the table while completing the experiment. Procedure Running Account Observations Procedure you plan to follow goes in this column. Changes to procedure, actual quantities, etc. go in this column Observations go in this column. Extraction Dissolve 0.25 g of the crude sample received with 30 mL of hexane. Transfer into a separatory funnel (125 mL) and keep the remaining crude for the other tests. Mix the solution well and then add 10 mL of saturated NaCl solution. Let those layers separate. Drain the aqueous layer into a beaker, and make sure to remove the stopper when draining the funnel. Unknown: 17 0.245 g Orange crystalline substance that has no inherent smell. Hexane is strong smelling and conforms to its space like water. With the organic layer (top), combine and wash with 10 mL of water. Combine the organic layer with the aqueous layer again. Wash the organic layer with 10 mL of NaCl, then drain the new aqueous layer back into the beaker with the combined aqueous layer. Dry the Organic Layer using MgSO4 and a vacuum filter. 0.051 g of organic crude product. The separation of layers resembles that of oil. However, with every new addition of NaCl, the mixture creates greater separation; appearance- wise, a darker orange hue is contributed. Percent Recovery: Percent recovery= (pure product mass/ crude product mass)*100 Percent recovery= 0.051 g /0.245 g (10/11) = 0.2290 x 100 = 22.9% Percent Recovery Recrystallization Alex Lei - Apr 08, 2023, 11:35 AM PDT Exp 0: Technique Review/PreLab/InLab 12 of 16

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Heat 20 ml of water and ethanol, and make sure neither begin to boil on the hot plate (separate flasks). Consider placing a watch glass on both beakers to avoid fast evaporation (slow the process). Recrystallize 0.25 g of the crude mixture by slowly combining small portions of the hot ethanol into an Erlenmeyer containing the crude mixture. Add ethanol until all the solid is completely dissolved. Add water dropwise into the solution until slight cloudiness persists. Swirl the flask while doing so. Add ethanol again until the slight cloudiness disappears. 0.301 g of crude measured crystals Crystals formed on the walls of the flask, but no immediate changes to the solution occurred besides this. The solution started to recrystallize after 5 minutes into the solution. Let the solution cool to room temperature and place it in an ice bath to complete recrystallization. Vacuum filter the solids and rinse with ice-cold water. Allow the solids to dry in the filter funnel for roughly 15 minutes while pulling air. 0.085 g of recrystallized Percent Recovery: Percent recovery= (pure product mass/ crude product mass)*100 10:1 (10/11) Percent recovery= 0.085g /0.301g (10/11) = 0.311 x 100 = 31.1 % recovery TLC Combine the solids into dry test tubes with the extracted solid and the recrystallized solids. Dissolve 1 mL of dichloromethane with each and run a TLC test using a sample solution of 10 mL. The ratio may vary, so try 4:1 hexane: ethyl acetate. RF value Calculations: Crude 5.56/6.00 = 0.9267 cm Extraction 5.56/6.00 = 0.9267 cm Recrystallization 5.56/6.00 = 0.9267 cm For TLC, a 4:1 ratio was used. It turns out that all 3 compound forms shared the same/equivalent spots as each other. The crude spots contain a second spot, which could signify a possible impurity. Exp 0: Technique Review/PreLab/InLab 13 of 16

Visualize the TLC spots using UV light. Melting Range (optional) Determine the melting point of the original crude and recrystallized substances. Take a mixed melting point of the compounds isolated from extraction with 2 standards (naphthalene standard and a second mixed melting point with biphenyl standard). You must have the melting point for 4 different things: Crude + Standards (x2) Recrystallized + Standards (x2) Extraction Flowchart Renee Link - Mar 26, 2022, 12:29 PM PDT Alex Lei - Apr 05, 2023, 1:44 PM PDT Exp 0: Technique Review/PreLab/InLab 14 of 16

Answers to Red Questions from Handout Renee Link - Mar 26, 2022, 12:30 PM PDT Extraction What is the appropriate way to vent a separatory funnel? By opening the tap while the separatory funnel is inverted. Point it away from the individual. What is an emulsion? How does using brine help with an emulsion? Emulsion is a combination of two compounds that do not fully mix together, making them immiscible. Brine will actively disperse the water droplet sand to produce better/more homogeneous emulsion mixtures. If you are not sure which layer is the aqueous layer, what can you do to determine that? To determine which layer is the aqueous layer, you can perform a water drop test; in theory, the aqueous layer will mix with the water droplets. Focus on which layer increases with the addition of water. What does wash mean in this context? Washing removes unwanted compounds from the mixture due to the concept of immiscibility. How can you tell when you have added enough drying agent? You will know that enough drying agent has been added because active clumping will cease, and moisture will disperse. How is liquid-liquid extraction different from acid-base extraction? Solutes are transferred from one liquid to another in liquid-liquid extraction. Meanwhile, the solute transforms in composition and moves from the organic to the aqueous layer with acid-base extraction. Recrystallization Why is it important to keep the solution warm? Keeping the solute warm will prevent the premature formation of crystals and avoid the inclusion of impurities from occurring more rapidly. What will happen if you add too much solvent? Adding too much solvent may create too much unnecessary dilution, resulting in fewer overall crystals produced. What can you do if you add too much solvent? If too much solvent is added, cool the flask to room temperature and put it in an ice bath. This can cause progressive evaporation. What does the cloudiness being present mean? Cloudiness signifies the saturation of the solution with the solute. (products separating from the solute). Why does the cloudiness disappear? Cloudiness disappearing signifies the return of the solution back to maximum levels of solubility. Why don’t we just put the solution directly into the ice bath without cooling to room temperature first? Rapid placement of the solution into the ice bath too fast will cause rapid cooling of the crystals, resulting in impurities. Why is it important to rinse the crystals? Rinsing crystals helps maintain the solid form of the crystals produced. Why is it important that the water is ice-cold? Rinsing crystals with ice-cold water will help purify the solids. TLC In what order do you expect the compounds to appear on the plate? Why do you predict this order? The order of appearance on the TLC plate will depend on polarity. More polar molecules will travel shorter distances (absorbed into the plate). Alex Lei - Apr 05, 2023, 2:18 PM PDT Exp 0: Technique Review/PreLab/InLab 15 of 16

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Why can UV light be used to visualize the compounds? UV light can be used to visualize TLC compounds because fluorescent interactions can be visualized from the different compounds. Melting range - Do these questions even if you don't do this part in lab. What would an appropriate starting temperature, ending temperature, and ramp rate be for naphthalene and biphenyl? A good starting temperature would be 80' C for naphthalene and 70'C for biphenyl. End temperatures would be at 83' for naphthalene and 72' for biphenyl. The effective ramp rate would be What is a “mixed melting point?” How does it give us information about the identity of a compound? Mixed melting point helps identify the compounds in question. Based on how vast or narrow the mixed melting point appears, it is known (can be determined) if the compounds in question are pure or impure. Experiment Summary Renee Link - Mar 26, 2022, 12:38 PM PDT Write a brief summary (~5 sentences) of your data, explaining whether your separations were successful. Remember to back up your claims with evidence from the data you collected. Separations for this experiment were inconclusive (at first) in whether success was obtained or not. On one hand, the data from our recrystallization showed a percent recovery value of 31.1% signifying the presence of possible errors that occurred with the formation of the recrystallized product; this could be a consequence of too much ethanol added or too rapid of a reaction occurring in higher temperatures. Amidst the incredibly low value for the percent recovery, however, the data that our group received from the TLC plate was nonetheless successful in determining a few factors of our separation; the crude sample (17) was impure but conclusively nonpolar and along with this, it was shown that the separation of whatever impurities had been present in the assigned sample was separated effectively. The extraction portion of our experiment yielded a low 22.9 % recovery value, but it is now known that the orange aqueous impurity of the substance was extracted, hence the lack of secondary spots noticed on the TLC slide. Further tests would need to be processed to conclusively verify if the unknown substance is what was predicted, due to the low presence of the recovery seen with recrystallized/extracted products, but otherwise, the separation showed promising recourse for what was intended to be accomplished in the separation done for this lab. Alex Lei - Apr 08, 2023, 11:35 AM PDT Exp 0: Technique Review/PreLab/InLab 16 of 16