CHEM 121 Lecture Notes - Petri Dish, Purified Water, Litmus

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CHEM 121 Full Course Notes

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The initial mass of aluminum is required to calculate the theoretical yield: add koh solution into a beaker over a hotplate containing the aluminum pieces under the fume hood. The hotplate will speed up the dissolution process. Stirring the beaker will also help the dissolution process. Do this under the fume hood because hydrogen gas is produced in the reaction: 2al(s) + 2koh(aq) + 6h2o(l) . 2al(oh)4- (aq) + 2k+aq) + 3h2(g): make sure that the solution is not over 30ml. If the solution is over 30ml, you can evaporate some of the water out using the hotplate (at a later step): remove any impurities from the solution by vacuum filtration. The filter flask should be extremely clean so that impurities do not alter the concentration or volume of your solution. Make sure you do this step while the solution is still hot so that the impurities don"t cool down and dissolve.

Related Questions

Part 1: Separation of Iron filings

Mass a watchglass and record
Obtain a Kimwipe tissue from the top of the benches and a rodmagnet
Wrap the Kimwipe tissue around the magnetic end, holding thetissue tight to the rod magnet.
Swirl the Kimwipe in your mixture. Knock off excess sand beforemoving on to step 5
Carefully over the watch glass remove the Kimwipe tissue fromthe magnet so the iron falls on the the watch glass
Repeat steps 4 and 5 two more times, make sure you record howsuccessful this separation was ï¿½ does the evaporating dish containonly iron?
Mass the watchglass and the collected iron.
Dispose of the iron in the hood.

Part 2: Separation of N

Mass a clean, dry, evaporating dish.
Pour the leftover mixture from step 1 into the evaporating dishand mass.
Place the evaporating dish on a hot plate in the hood.
Gently and slowly heat the mixture until the white fumes cease.Be patient. Depending on the amount of ammonium chloride in yoursample, this could take quite a while. A half our would not beunheard of.
Stir the mixture frequently to facilitate the sublimation ofthe ammonium chloride. This is crucial in order to obtain goodresults. (Use crucible tongs to hold onto the dish so it doesnï¿½tmove as much)
After the white fumes disappear, turn off the hot plate andremove the evaporating dish with crucible tongs and let it cool inthe hood.
When the evaporating dish is cooled, mass the left overmaterial and the evaporating dish.

Part 3: Determining the amount of NaCl.

Measure 10 mL of distilled water in a graduated cylinder.Slowly add the water to the mixture in the evaporating dish whilecontinuously stirring with a clean, glass stirring rod. Afteradding all of the water, stir for 2 min more.
Assemble the gravity filtration apparatus shown in Figure1.
Fold a piece of filter paper as shown in Figure 2. Open up thepaper cone, and place it in the filtering funnel.

Position a beaker under the funnel, making sure that the funnelstem is touching the inside wall of the beaker. Pour as much of thesupernatant liquid as possible from the evaporating dish intofunnel. Collect the filtrate in the beaker.
Transfer the solid remaining in the evaporating dish into thefunnel, using a stream of distilled water from a wash bottle, asshown in Figure 3.
Re mass the watchglass from Part 1 and record this mass.
Pour the filtrate in the beaker into the evaporating dish
Place the evaporating dish containing the filtrate on a hotplate. Begin heating the solution.
While the solution is heating to boiling, move onto Part 4

Carefully remove the filter paper and residue from the funnel.Place the paper and residue onto the watchglass.
Place the watchglass with the filter paper and sand on top ofthe boiling salt solution to dry the sand
Keep the salt water boiling, until there is just a little bitof water left, or popping sounds are heard, then turn off the hotplate, and allow the heat from the hot plate to finish evaporatingand drying your salt.
Allow the evaporating dish and its contents to cool to roomtemperature.
Obtain another watch glass and mass.
Transfer the dried sand and filter paper from original watchglass (caution, salt has spattered onto this watch glass, so donï¿½tknock any off, that is product you will need) onto the new cleanmassed watch glass. Replace the original watch glass onto thecooling evaporation dish
Mass the new watch glass, sand and filter paper all together.Discard filter paper and sand into garbage. Observe how pure yoursand looks.
After evaporating dish has cooled, determine the mass of theevaporating dish, watch glass plus NaCl. Record this mass. Then,discard the NaCl as directed. Wash evaporating dish and watch glassto dissolve the salt.
Observe how pure your salt looks.

Result and Discussion: Separation Lab

Substance	Grams recovered	% mass
Fe
NH4Cl
NaCl
SIO2

Overall percentRecovery:

A) Explain what steps(s) youcould have improved (and how) to help your percentrecovery.

b) Write a paragraph about thelab include briefly what was done, your result, were you correctand possible experimental errors- do not state human measurementerrors as errors. Be Specific, what specific human errors occurred,what measurement errors occurred, what process in the experimentcould errors have occurred.

ACYLATION OF AN AROMATIC AMINE

Prepare a solution of 2.5 g of p-toluidine, 65 mL of water, and2.5 mL of concentrated

hydrochloric acid in a 125 mL Erlenmeyer flask. Be sure to placethe reagents in the flask in that

order! Using a warm hot plate to assist you, swirl the contentsof the flask until all of the solid

dissolves. The purpose of the acid is to protonate thep-toluidine and increases its solubility in

water.

In a small beaker, dissolve 3.75 g of sodium acetate trihydratein 7 mL of water. Again,

use a warm hot plate to speed up the process, if necessary. Thepurpose of the sodium acetate is

to buffer the solution. We want the pH such that the carbonylgroup is electrophilic but some of

the amine group is not protonated. A protonated carbonyl groupis more susceptible to

nucleophilic attack, while the amino group can only act as anucleophile when it is not

protonated.

Heat the p-toluidine hydrochloride solution to 50 ?C using a hotplate. While stirring or

swirling rapidly, add 2.5 mL of acetic anhydride from a burettein the hood. Then add the

sodium acetate solution prepared above. Once the solution isthoroughly mixed, cool the flask in

an ice-water bath. A white precipitate should form. Collect thissolid via vacuum filtration.

While the solid is on the filter paper, wash it three times withcold water. After washing the

solid, remove as much of the water from the product by suctionfiltration as possible. Once the

product is fully dry, determine the mass, measure the meltingpoint and calculate the percent

yield. Let your Teaching Assistant evaluate your product anddispose of it properly

please please please please help me do allthese:

calculate the limiting reagent and

the theoretical yield

and the chemical balanced equation

Organic chemistry

Part1

Question1:

Page 1 of 3 In this session you will carry out two experiments to demonstrate chemistry of the carbonyl group. The two step synthesis of an amide from a ketone in Part 1 involves a nucleophilic addition reaction. In Part 2 you will convert an unknown amine to an amide using Part 1 Two Step Synthesis of an Amide from a Ketone This laboratory activity involves the synthesis of an amide from a ketone in two steps. In the first step, benzophenone is converted to diphenylmethanone oxime (Scheme. This reaction is a straightforward nucleophilic addition of an amine to a carbonyl that occurs with elimination of a water molecule. In the presence of phosphorus pentachloride, the oxime e (Scheme 2). The mechanism for the second step is less straightforward and your demonstrator will discuss it with you during the laboratory class. The intermediate oxime and the amide final product have the same molar mass and molecular formula, you will see how they may be differentiated using spectral data. 0 N-OH 1. HONH2H, NaOH + H20 Scheme 1 Scheme 2 Conversion of the ketone to an oxime (nucleophilic addition) Place the following in a 50 mL round bottom flask: Benzophenone (2.5 g), hydroxylamine hydrochloride (1.5 g), ethanol (5 mL) and water (1 mL). Add sodium hydroxide pellets (2.8 g) in portions with swirling and if vigorous reaction occurs, cool the flask under running tap water, When all the sodium hydroxide has been added, attach a reflux condenser and boil the mixture for 5 minutes. Allow the mixture to cool while you prepare an acidic solution by adding concentrated hydrochloric acid (7.5 mL) to water (50 mL) in a 100 mL beaker. Pour the cooled reaction mixture into the acidic solution and isolate the precipitate using vacuum filtration. Wash the solid with cold water and dry in an oven at 40Â°C or in a vacuum desiccator. Record the melting point and the yield of the oxime. Using the balance in the fume hood, rapidly weigh out phosphorus pentachloride (2.5 g) into a plastic vial. In a 100 mL conical flask dissolve the oxime prepared earlier (2.0 g) in dry diethyl ether (30 mL). Cool the flask in an ice bath and add about half of the phosphorus pentachloride. When the heat generated in the reaction subsides, add another small portion of phosphorus pentachloride and continue this process until all the material has

CHEM 121 Lecture Notes - Petri Dish, Purified Water, Litmus

CHEM 121 Full Course Notes

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