Distillation & BP

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61 5. Distillation and Boiling Points Read the introduction and the appropriate experiments below. You will be doing either Procedure 1A or 1B or 2A or 2B (see desk assignment below.) In your lab notebook using carbon copies, you are ONLY required to write the PRELAB section for the experiments that you will actually be running in the laboratory. Your experiment assignment can be determined according to the following diagram: Hood Hood Hood Hood Windows Hall 1A 1A 2B 2B 2A 2A 1B 1B End desks closest to the window will do Exp't 1A Inside desks closest to the window will do Exp't 2B Inside desks closest to the hall will do 2A End desks closest to the hall will do 1B All students will do Procedure 3, microscale fractional distillation of mixture of two unknown liquids. You will share your data from Procedures 1 or 2 with the three other students on your side of the lab bench. You will then be able to compare the efficiency of simple versus fractional distillation for two different systems: toluene/cyclohexane and ethanol/water. In your lab notebook, using carbonless copies, write an introductory PRELAB section for the distillation experiment including: 1. A brief Summary of what will be done and why it will be done for the experiments below. 2. Three Learning Objectives or Goals for the experiment. 3. Diagrams of Apparatus. There are no chemical reactions in this experiment. 4. Chemical Data Tables Complete the rest of your Common Shelf Chemical Data Table and turn in a photocopy of it with your PreLab. You should look up the chemicals not on the Chemical Shelf Chemical Data Table (acetone, 1-butanol, 2-methyl-2-propanol (t-butyl alcohol) and enter them into a blank Chemical Data Table from the back of your notebook. Sharing data PreLab Exercise Mole % Isoamyl Acetate 100 75 50 25 0 Mole % Methyl Benzoate 100 75 50 25 0 200 190 180 140 170 160 150 Temp o C Vapor Liquid 200 190 180 140 170 160 150 1. What is the initial boiling point of this liquid mixture? 2. What is the composition of the vapor in equilibrium with the liquid? What is the composition of the initial condensate from simple distillation? 3. If the same mixture were fractionally distilled, how would the composition of the first liquid collected be different from the initial condensate disucssed in question 2 above? 5. PreLab Exercise A mixture of 10 mL of isoamyl acetate (MW=130.2 g/mol and density=0.88 g/mL) and 15 mL of methyl benzoate (MW=136.2 g/mol and density=1.09 g/mL) is distilled. Calculate the mole percent for each component. Use these mole %’s and the figure below to answer the following questions. The point breakdowns can be found on the grading sheet in Appendix A.4.

description

about the distillation experiment

Transcript of Distillation & BP

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5. Distillation and Boiling PointsRead the introduction and the appropriate experiments below. You will be doing either

Procedure 1A or 1B or 2A or 2B (see desk assignment below.) In your lab notebook using carboncopies, you are ONLY required to write the PRELAB section for the experiments that you willactually be running in the laboratory.

Your experiment assignment can be determined according to the following diagram:

Hood

Hood

Hood

Hood

Win

dow

s

Ha

ll1 A

1A

2B

2B

2 A

2A

1B

1B

End desks closest to the window will do Exp't 1A

Inside desks closest to the window will do Exp't 2B

Inside desks closest to the hall will do 2A

End desks closest to the hall will do 1B

All students will do Procedure 3, microscale fractional distillation of mixture of two unknownliquids. You will share your data from Procedures 1 or 2 with the three other students onyour side of the lab bench. You will then be able to compare the efficiency of simple versusfractional distillation for two different systems: toluene/cyclohexane and ethanol/water.

In your lab notebook, using carbonless copies, write an introductory PRELAB section for thedistillation experiment including:

1. A brief Summary of what will be done and why it will be done for the experiments below.2. Three Learning Objectives or Goals for the experiment.3. Diagrams of Apparatus. There are no chemical reactions in this experiment.4. Chemical Data Tables Complete the rest of your Common Shelf Chemical Data Table and

turn in a photocopy of it with your PreLab. You should look up the chemicals not on theChemical Shelf Chemical Data Table (acetone, 1-butanol, 2-methyl-2-propanol (t-butylalcohol) and enter them into a blank Chemical Data Table from the back of your notebook.

Sharing data

PreLab Exercise

Mole % Isoamyl Acetate 100 75 50 25 0

Mole % Methyl Benzoate 1007550250

200

190

180

140

170

160

150

Temp oC

Vapor

Liquid

200

190

180

140

170

160

150

1. What is the initial boiling point of this liquid mixture?

2. What is the composition of the vapor in equilibrium with the liquid? What isthe composition of the initial condensate from simple distillation?

3. If the same mixture were fractionally distilled, how would the composition ofthe first liquid collected be different from the initial condensate disucssed inquestion 2 above?

5. PreLab ExerciseA mixture of 10 mL of isoamyl acetate (MW=130.2 g/mol and density=0.88 g/mL) and15 mL of methyl benzoate (MW=136.2 g/mol and density=1.09 g/mL) is distilled.Calculate the mole percent for each component. Use these mole %’s and the figure belowto answer the following questions.

The pointbreakdowns canbe found on thegrading sheet inAppendix A.4.

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IntroductionDistillation is an excellent method for purifying a liquid. A liquid contains closely packed but

mobile atoms or molecules of varying energy. When a molecule of the liquid approaches thevapor-liquid phase boundary, it may, if it possesses sufficient energy, pass from the liquid phaseinto the gas phase. Only molecules energetic enough to overcome the forces which hold them inthe liquid phase can escape into the vapor phase.

Some of the molecules present in the vapor phase above the liquid may, as they approach thesurface of the liquid, enter the liquid phase and thus become part of the condensed phase. In sodoing, the molecules relinquish some of their kinetic energy (i.e. their motion is slowed). Heatingthe liquid causes more molecules to enter the vapor phase; cooling the vapor reverses this process.

When the system is in equilibrium, as many molecules are escaping into the vapor from theliquid phase as are returning from the vapor to the liquid. The extent of this equilibrium ismeasured as the vapor pressure. If the system maintains equilibrium even when the energy isincreased, more molecules in the liquid phase have energy sufficient to escape into the vaporphase. Although more molecules are also returning from the vapor phase, the number ofmolecules in the vapor phase increases and so does the vapor pressure. The exact number ofmolecules in the vapor phase depends mainly on the temperature, the pressure, and the strengthof the intermolecular forces exerted in the liquid phase and the volume of the system.

If two different components (designated A and B) are present in the liquid phase, the vaporabove the liquid will contain some molecules of each component. The number of A moleculesin the vapor phase will be determined by the vapor pressure of A and by the mole fraction of Ain the mixture. In other words, the relative amounts of the components A and B in the vapor phasewill be related to the vapor pressure of each pure liquid. This relationship is expressedmathematically as Raoult’s law:

Ptotal

= PA + P

B where P

A = P°

AN

A and PB = P°

BN

B

PA = partial pressure of A

PB = partial pressure of B

P°A = vapor pressure of pure A

P°B = vapor pressure of pure B

NA = mole fraction of A in the liquid

NB = mole fraction of B in the liquid

The total vapor pressure above the liquid mixture is the sum of the two partial pressures ofcomponents A and B. As the temperature is raised, the vapor pressure of each componentincreases, thereby proportionately increasing the total vapor pressure above the liquid. At sometemperature the sum of the partial pressures equals 760 torr (1 atm) and the solution begins to boil.More generally, the boiling point is defined as that temperature where the sum of partial pressuresabove the liquid equals the externally applied pressure on the system. Lowering the externalpressure causes the solution to boil at a lower temperature - raising the external pressure causesthe solution to boil at a higher temperature. Raoult’s law also provides information as to thecomposition of the vapor above a liquid:

XA = mole fraction of A in the vapor = P

A/P

total

XB = mole fraction of B in the vapor = P

B/P

total

Raoult's Law ofPartial Pressures

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Simple Distillation: Distillation occurs when a liquid is heated in a vessel and the vapors arepassed through a condenser, allowing the vapors to convert back to a liquid (see Figure 5.1.) whichflow into a different vessel from that used for the heating. A simple distillation is considered tobe any distillation which does not involve a fractionating column or one in which an one liquidcomponent is separated either from non-volatile substances or another liquid that differs in boilingpoint by at least 75°. The condensate will have essentially the same mole ratio of liquids as thevapor boiling from the liquid. Simple distillation is not effective in separating closely boilingcomponents of a mixture.

Fractional Distillation: If a fractionating column is used in the distillation (see Figure 5.3)it is possible to separate compounds with closer boiling points. The fractionating column ispacked with some porous material (chore boy) which provides a large surface area for the multiplecondensations and vaporizations to occur as the liquid ascends the column. Condensing of thehigher-boiling vapor releases heat causing the vaporization of lower-boiling liquid on the packingso that the lower boiling component moves up while the higher boiling componenet moves down,some of it running back into the distilling flask. Each successive condensation/vaporization cycleaffords a vapor that is richer in the more volatile fraction. As the temperature is raised the lowerboiling fractions get enriched in the vapor. Consider a 60:40 mixture of cyclohexane (BP 81 °C)and toluene (BP 110 °C). This will boil at 88°C. The vapor above this boiling mixture wouldconsist of a 83:17 mixture of cyclohexane and toluene. The material then recondenses on the choreboy. The re-vaporization of this material at 83°C produces a vapor with a 95:5 cyclohexane:tolueneratio. This process is depicted graphically in Figure 5.1 below. The lower curve represents thecomposition of the liquid and the upper curve the composition of the vapor corresponding to thatliquid composition determined by drawing a horizontal line. A couple more cycles of condensationand vaporization will render the cyclohexane essentially pure. Each cycle is called a theoreticalplate. The fractionating columns used in the organic labs have about 3 to 5 theoretical plates.

Figure 5.1: Liquid/Vapor Distillation Temperature-Composition Curvesfor Cyclohexane:Toluene mixtures

liquid composition curve

vapor composition curve

90

100

110

20 40 60 80 100

% Toluene

0

80

liquid-vaportemperature

°C

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Azeotropes: Not all mixtures of liquids conform to Raoult’s law. For example, ethanol andwater, because of molecular interactions, form an azeotrope. A mixture of 95.5% ethanol and 4.5% water boils below the boiling point of pure ethanol, and thus 100% ethanol cannot be preparedby distillation. A mixture of liquids of a certain definite composition that distills at a constanttemperature without change in composition is called an azeotrope.

bp of pure B

simpledistillation

fractionaldistillation

bp of pure A

Tem

pera

ture

( C

)o

Distillation Curves: If one plots the course of a simple and a fractional distillation (usingcorrected thermometer readings), curves approximating those shown below in Figure 5.1 willresult. These curves provide information as to the efficiency of the separation of components ofa mixture. Another advantage of fractional distillation is that the flat portions (plateaus) of thegraph of boiling point (Y axis) vs distillate volume (X axis) can be more easily distinguished thanin a simple distillation. Therefore, the boiling points are more accurate and can be used to helpidentify the boiling fractions.

Distillate Volume in mL or drops

The following experiments are designed to give you exposure to a number of different techniquesusing a variety of equipment including macroscale simple and fractional distillation, andmicroscale fractional distillation of an unknown two-component mixture to determine boilingpoints and thus identify the two liquids.

Figure 5.1: Simple vs. Fractional Distillation Data.

Simple andFractionalDistillation Curves

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Experimental ProceduresCaution!In any distillation the flask should not be more than two-thirds full at the start. Great

care should be taken not to distill to dryness! There always exists the possibility thatcertain liquids, especially ethers, contain some explosive peroxides formed byexposure to air. These are higher boiling and can concentrate in the distilling flaskas you distill. If you distill all the liquid from the flask, the temperature will rise veryhigh, and this could cause the peroxides to explode violently.

DO NOT TRY TO TEAR "CHORE BOY" WITH YOUR HANDS! DEEP CUTS WILLRESULT! Use scissors from the Side-shelf.

Checking theThermometer.

Correcting forPressureEffects.

connectingtube

rubber bandto holdadapter on

glassadapter forrubberthermometeradapter

westcondenser

100 mL flask with1" stir bar in it

heating mantle

ring stands

3-wayconnectingtube

rubberthermometeradapter

magneticstirrer

Varistat

water in

DistillationReceiver:10 mLgraduatedcylinder

water out

Occasionally the temperature scale on your thermometer may be inaccurate. It should bechecked by measuring the known boiling and freezing points of a liquid such as water. All thepeople on one side of the bench can share one hot plate with boiling water bath to check the 100°Cpoint (corrected for atmospheric pressure, see next paragraph) and can also share one ice-waterbath to measure the freezing point of water, 0°C. If either is off by more than 1°C, you shouldobtain another thermometer from the stockroom.

Liquids boil lower if the atmospheric pressure is less than 760 Torr and higher if it is greater.To obtain a boiling point corrected to atmospheric pressure, add (or subtract) 0.5°C to theobserved boiling point for every 10 Torr the observed atmospheric pressure is below (or above)760 Torr. For example, if your thermometer is accurate (see above) and reads 108°C for theboiling point of toluene when the barometer reading is 720 Torr, the corrected boiling point oftoluene would be about 110°C (at 760 Torr). A barometer (with instructions for use) is availableat the south end of Lab 215.

Figure 5.2: Set-up for macroscale simple distillation.

Simple Distillation

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Procedures 1A and 1BAssembling theDistillation Set-upfor SimpleDistillation.

Procedure 1A

Assemble the apparatus for simple distillation as shown in Figure 5.2. Start by placing yourmagnetic stirrer on the base of a ring stand and then attaching the electric heating mantle (withoutsand in it) to the ring stand so it rests on top of the stirrer. Plug the heating mantle into the Varistat,a variable voltage controller, on the side of the hood and plug the Varistat into the socket aboveyour bench. Place a 1" stirring bar in a dry 100 mL round-bottomed flask from your blue kit andclamp this to the ring stand so that it fits snugly in the heating mantle. Stirring promotes evenboiling and avoids “bumping”. As you assemble the apparatus, each ground joint is lightlygreased by putting a very small dab of grease on the inner joint and spreading it over the surfaceof the joint. (Do not use excess grease as it will contaminate the product.) When pressed into theouter joint and twisted, the connection should appear almost transparent.

Water enters the condenser at the connection nearest the distillation receiver. Because of thelarge heat capacity of water only a very slow flow is needed; too much water pressure will causethe tubing to pop off, causing a flood (and you will probably also get a shower). The condensershould be clamped to a separate ring stand. Rubber bands (Common Shelf) can be used to holdthe angled connecting tube to the condenser. Collect the distilled liquid in a 10 mL graduatedcylinder. This will have to be emptied into an Erlenmeyer flask a few times during the distillation.Be sure that the bulb of the dry thermometer is just below the opening into the side arm of thedistillation head.

Caution: Cyclohexane and toluene are flammable; make sure distilling apparatus isvapor-tight.

Remove the glass thermometer adapter and place a long-stem glass funnel in the 3-wayconnecting tube. Into this funnel, pour in a mixture of 25 mL of cyclohexane and 25 mL of toluene.Reassemble and after making sure all connections are tight, turn the magnetic stirrer on (lowestsetting) and heat the flask strongly (Varistat setting = 70) until boiling starts. Then adjust the heatuntil the distillate drops at a regular rate of about one drop per second. Record temperature versustotal volume of distillate at regular intervals, about every 2 mL. After 40 mL of distillate arecollected, discontinue the distillation. Record the barometric pressure.

Exchange data with the three other students on your side of a lab bench and record thedistillation data so you have it for all four experiments: 1A, 1B, 2A, and 2B.

Cleaning Up Dispose of cyclohexane and toluene in the recycling containers provided. Donot pour them down the drain.

Simple Distillationof a Cyclohexane-Toluene Mixture.

Cleaning Up

Procedure 1BSimple Distillationof an Ethanol-WaterMixture.

Cleaning Up

Remove the glass thermometer adapter and place a long-stem glass funnel in the 3-wayconnecting tube. Into this funnel, pour 50 mL of 20% ethanol/80% water. Reassemble and aftermaking sure all connections are tight, turn the magnetic stirrer on (lowest setting) and heat theflask strongly until boiling starts. Then adjust the heat until the distillate drops at a regular rateof about one drop per second. Record temperature versus total volume of distillate at regularintervals, every one or two mL.

After about 25 mL of distillate are collected, discontinue the distillation. Record thebarometric pressure, make any boiling point correction necessary, and plot boiling point versusvolume of distillate.

Exchange data with the three other students on your side of a lab bench and record thedistillation data so you have it for all four experiments: 1A, 1B, 2A, and 2B.

Cleaning Up Dispose of distillate in the ethanol/water recycling containers provided. Thedistillation flask residue can be flushed down the drain.

Caution!

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Procedure 2A and 2BAssemble the apparatus for fractional distillation as shown in Figure 5.3. Start by placing your

magnetic stirrer on a ring stand and then attaching the electric heating mantle (without sand init) to the ring stand so it rests on top of the stirrer. Plug the heating mantle into the variable voltagecontroller (Varistat), on the side of the hood and plug the varisatat into the socket above yourbench. Place your 1" stirring bar in a dry 100 mL round-bottomed flask from your blue kit andclamp this to the ring stand so that it fits snugly in the heating mantle. Stirring promotes evenboiling and avoids “bumping”. As you assemble the apparatus, each ground joint should belightly greased by putting a very small dab of grease on the inner joint and spreading it over thesurface of the joint. (Do not use excess grease as it will contaminate the product.) When pressedinto the outer joint and twisted, the connection should appear transparent.

Assembling theDistillation Set-upfor FractionalDistillation.

Figure 5.3: Set-up for macroscale fractional distillation

rubberthermometeradapter

magneticstirrer

heating mantle

100 mL flask with1" stir bar in it

distillingcolumnhalffull withmetalhelices

steelwool

westcondenser

Varistat

fractionatingcolumnwrappedwithglasswoolto preventheatloss

3-wayconnectingtube

water out

glassadapter forrubberthermometeradapter

rubber bandto holdadapter on

pipetbulb ring stands

water in

DistillationReceiver:10 mLgraduatedcylinder

connectingtube

MacroscaleFractional

DistillzationApparatus.

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The distilling column is packed by first pushing a wad of stainless steel sponge ("ChoreBoy")through from the larger end of the column until it rests against the three indents near the smallerend. Then stainless steel chips are added until the fractionating column is about one-third to one-half full. The column should be perfectly vertical and one of the two water connections shouldbe sealed with parafilm, a wad of tissue or a pipet bulb. To get higher boiling liquids through thefractionating column, you must insulate it and the boiling flask by wrapping it with glass wool.

Water enters the condenser at the connection nearest the distillation receiver. Because of thelarge heat capacity of water only a very slow flow is needed; too much water pressure will causethe tubing to pop off, causing a flood. The condenser should be clamped to a separate ring stand.Rubber bands (Common Shelf) can be used to hold the bent connecting tube to the condenser.Collect the distilled liquid in a 10 mL graduated cylinder. This will have to be emptied into anErlenmeyer flask a few times during the distillation. Be sure that the bulb of the thermometer isjust below the opening into the side arm of the distillation head.

Caution! Do not tryto tear Chore Boywith your hands!Deep cuts mayresult. If necessary,scissors areavailable at thestockroom.

Caution: Cyclohexane and toluene are flammable; make sure distilling apparatus isvapor-tight.

Remove the glass thermometer adapter and place a long-stem glass funnel in the 3-wayconnecting tube. Into this funnel, slowly pour 25 mL of cyclohexane and 25 mL of toluene.Reassemble the apparatus and make sure all connections are tight. Turn on the magnetic stirrerto its lowest setting.

Start heating the flask at a Varistat setting of 60 until the mixture of cyclohexane and toluenejust begins to boil. As soon as boiling starts, turn down the power slightly. Heat slowly at first.A ring of condensate will rise slowly through the column. The rise should be very gradual so thatthe column can acquire a uniform temperature gradient. Do not apply more heat until you are surethat the ring of condensate has stopped rising; then increase the heat gradually. In a properlyconducted operation, the vapor-condensate mixture reaches the top of the column only afterseveral minutes.

Once distillation has commenced, it should continue steadily, without any drop in temperature,at a rate not greater than 1 drop every 2 or 3 sec (2 mL in 1.5-2 min). Observe the flow and keepit steady by slight increases in heating as required. Record the temperature as each milliliter ofdistillate collects, and make more frequent readings when the temperature starts to rise abruptly.

Record temperature versus total volume of distillate at regular intervals. Stop the distillationwhen a second constant temperature is reached. Record the barometric pressure and what youobserved inside the column in the course of the fractionation.

Exchange data with the three other students on your side of a lab bench and record thedistillation data so you have it for all four procedures: 1A, 1B, 2A, and 2B.

Cleaning Up Dispose of distilled and undistilled cyclohexane and toluene in the recyclingcontainers provided. Do not pour them down the drain.

Cleaning Up

Procedure 2A

FractionalDistillation of aCyclohexane-Toluene Mixture.

Caution!

Procedure 2BRemove the glass thermometer adapter and place a long-stem glass funnel in the 3-way

connecting tube. Into this funnel, slowly pour approximately 50 mL of 20% ethanol/80% water.Reassemble and make sure all connections are tight. Turn the magnetic stirrer on to its lowestsetting. Follow the procedure (Ex 2A above) for the fractional distillation of a cyclohexane-toluene mixture.

After 25 mL of distillate are collected, discontinue the distillation. Record the barometricpressure and what you observed inside the column in the course of the fractionation.

Exchange data with the three other students on your side of a lab bench and record thedistillation data so you have it for all four procedures: 1A, 1B, 2A, and 2B.

Cleaning Up Dispose of distillate in the ethanol/water recycling containers provided. Thedistillation flask residue can be flushed down the drain.

Cleaning Up

Fractional Distilla-tion of an Ethanol-Water Mixture.

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Procedure 3

You will be supplied with an unknown that is a 50:50 mixture of two organic liquids selectedfrom those listed in Table 5.1 below. (Record the unknown number immediately in your labnotebook.) Using microscale fractional distillation, you will determine their boiling points andthis will allow the identification of the two liquid components of your unknown. The liquids inthe mixture will be mutually soluble and differ in boiling point by more than 20°C.

MicroscaleDistillation of anUnknown.

Solvent Boi l ingPoint °C

Acetone 56.5

Methanol 64.7

Hexane 68.8

1-Butanol 117.2

2-Methyl-2-propanol

82.2

Water 100.0

Toluene* 110.6

Table 5.1: Boiling Points of Possible Distillation Unknowns

* Methanol and toluene form an azeotrope, bp 63.8°C (69% methanol).

Set your magnetic stirrer on a ring stand and attach a heating mantle as you did in Ex 1 or 2except fill your heating mantle half full with sand. Start heating it at a varistat setting of 50. Toa 5-mL short-necked round-bottomed flask is added 4 mL of your distillation unknown and a half-inch (1/2 inch) magnetic stirring bar. Insert enough stainless steel Chore Boy into the distillationcolumn to fill it LOOSELY (see Figure 5.4.)

The thermometer bulb should be completely below the side arm of the distillation head so thatthe mercury reaches the same temperature as the vapor that distills. The thermometer willprobably need to be clamped with the 3-prong micro-clamp so that it doesn’t lean against theinside wall of the distillation head, which leads to erroneous temperature readings. The end of thedistillation head dips well down into a 20 mL vial, which rests on the bottom of a 50 mL beakerfilled with cold ice-water. The beaker is supported with a large clamp.

Turn on the magnetic stirrer (lowest speed) and start the fractional distillation by piling hot sandup around the flask with a spatula to heat it. As soon as boiling starts, the vapors can be seen torise up the neck of the flask. Adjust the rate of heating by piling up or scraping away sand fromthe flask bottom so that it takes several minutes for the vapor to rise to the thermometer: The rateof distillation should be no faster than three drops per minute. If your distillate vapors don’tseem to be condensing into drops, wrap a 2" x 2" strip of wet paper towel around the distilling headside arm to cool it by evaporation.

Caution! Do not tryto tear "Chore Boy"apart with yourhands! Deep cutsoften result! Use apair of scissors ifnecessary.

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Varistat magneticstirrer

20 mLvial

Distillationhead

Distillationcolumnice

water in50 mLbeaker

controlheating bymoving hotsandtoward oraway fromflask

5 mL flaskcontaining1 cm stir bar

Heatingmantlehalf fullwith sand

distillationcolumnwrappedwithglasswoolto preventheatloss

20 mLvial

stainlesssteelwool

Figure 5.4: Set-up for microscale fractional distillation of your unknown.

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Keep account of the total number of drops and record the temperature every few drops duringthe entire distillation. If the rate of distillation is as slow as it should be, there will be sufficienttime between drops to read and record the temperature. Only collect fractions in separate vialsif the boiling point data doesn’t match one of the possible liquids in Table 5.1. In this case, youmay need to do some other test. Stop the distillation as soon as you have enough data to determinethe boiling point of the higher boiling component.

Prepare a distillation curve of temperature versus number of drops (see Introduction above.)Identify the components from their boiling points. If the boiling points derived from yourfractional distillation do not allow unambiguous identification of both unknown components, trya simple solubility test: hexane and toluene are the only completely water-insoluble liquids givenas possibilities. Do not hesitate to ask your instructor for help.

Cleaning Up Dispose of water-insoluble unknown distillates in the Nonhalogenated OrganicsWaste containers. Water-soluble unknown distillates (water, acetone, methanol) can be flusheddown the drain. If necessary, test water solubility by squirting a few drops of water into thedistillate. Carry your sandbath to the side shelf and dump the HOT! sand back into the sand supplybowl. Do NOT dump it in the waste bins. Glass wool may be reused over and over; return glasswool to the supply container.

Final Report

Record data and observations in your notebook as you work (see the section The LaboratoryNotebook: OBSERVATIONS AND DATA section). For the RESULTS AND DISCUSSIONsection of your final lab report, follow the point distribution on the grading sheet for thisexperiment and be sure to include:

(1) Four distillation curves of macroscale simple and fractional distillation data taken byyou and the other students on your side of the bench. Make any atmospheric pressureboiling point corrections necessary, then plot boiling point versus volume of distillate(drops or mL) of the type shown in the curves in the Introduction .

(2) The distillation curve for your unknown.

(3) Give the identities of your two unknown liquids.

(4) Discussion of simple versus fractional distillation. Do the results support predictions?

PostLab Question:

The liquid boiling in a simple distillation flask consists of 80 mole percent of hexane and 20mole percent of n-propylbenzene. At 79°C a small amount of distillate is collected. The standardvapor pressures of pure hexane is 812 mm and pure n-propylbenzene is 560 mm Hg, respectively,at 79°C. Calculate the percentage of each of the two components in this fraction of distillate.Show your calculations.

A copy of the In-Lab and Post-Lab Sections of the Final Report Grading Sheet is on the nextpage.

Cleaning Up

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InLab and PostLab Sections - Final Report:

Accuracy and completeness of OBSERVATION/DATA section 8

RESULTS/DISCUSSION - Overall organization, readability, completeness8

Boiling points corrected for barometric pressure 8

Five plots of corrected distillation temperature versus distillation volume2 5

Identification of your two unknown liquids in your distillation mixture2 5

Discussion of simple versus fractional distillation; Do the results support pr1 6

PostLab Question 1 0

Total for Final Report 100