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IN THfi LAB*RATORY
Fundamen
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INSTRUCTOR'S
MANUAL
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FourthEdition
RalphA. Burns
St. LouisCommunityCollege,
MeramecCampus
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INTHELABORATOffryffi
Upper SaddleRiver,NJ 07458
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TABLE OF CONTENTS
PHYSICAL AND CHEMICAL CHANGES
I
MEASUREMENTS
)
DENSITY
3
QUANTITATIVE SEPARATIONOF A MIXTURE
5
MELTING POINT. A CHARACTERISTIC PROPERTY
6
CHROMATOGRAPHY
MOLAR MASSESOF SOME GASES
Experiment24:
9
ATOMS AND SPECTRA
10
CONDUCTIVITYAND SOLUBILITY PROPERTIES
13
MOLECULAR MODELS AND SHAPESOF MOLECULES
15
THE FORMULA OF A HYDRATE
l6
IONIC REACTIONS
18
TYPESOF CHEMICAL REACTIONS
20
THE PREPARATION OF ALUM FROM SCRAPALUMINUM
2l
GRAVIMETGRIC ANALYSIS OF A SOLUBLE SULFATE
))
THE PRESSUR-E-VOLULME
RELATIONSHIP FOR GASES
23
DETERMINATION OF THE MOLAR VOLUME OF A GAS
24
DIFFUSION,THE RACE BETWEEN GASES
2S
HEAT OF NEUTRALIZATION
26
HEAT OF SOLUTION
28
PERCENTAGEOF ACETIC ACID IN VINEGAR
29
ACIDS, BASES,AND pH
30
MOLECULAR MODELS: GETTING THE ANGLE
ON CARBON
31
ASPIRIN AND OIL OF WINTERGREEN
32
Laboratory Instructo r's Manual
Experiment 1: 'PHYSICAL AND CHEMICAL CHANGES
Chemicalsneededfor 24 studentsworking in pairs.
DISCUSS SAFETY
Iodinecrystals,20 to 50 g
Methylenechloride(or acetone,but color of iodine in acetone
is not as good), 100 mL
Magnesiumribbon,24 pieces,5 cm (2 in.) each
6 M Sulfuricacid, 250 mL in appropriatebottles
copper turnings,fine, enoughfor studentsto have48 marble-sizedballs
Lead(II) nitrate,solid,50 to 100g
Potassiumr,hronrate,
solid, 50 to 100g
d;chrrorn.!<OptionalInstructorDemonstration:
Show the brilliant purple-violetcolor of 2 or 3 iodine crystalsdissolved
in 4-5 mL of carbontetrachloride,in a medium-sizetest tube.
Equipmentneededfor eachworking pair of students.
150mL beaker
Ringstandand ring
250 mL beaker
Watch glass
Evaporatingdish
Wire gauze
Funnel(glass)
Scoopulaor forceps
Glassstirring rod
4 Medium size(15 x 125 mm) test tubes
4Large size(18 x 150 mm) testtubes
WhatmanNo. I filter paper, I I cm diameter
Answersto Questions: Physicaland ChemicalChanges
l. True
2. True
3. True
4. True
5. False
6. False
Answersto PRE-LAB or POST-LAB QUZ
l. physical
2. chemical
3. physical
4. chemical
5. physical
Teachingsuggestions. Have each pair of studentscheck with the instructor before leaving the
Iab. The instructor can ask for a verbal explanationof what was happening-a physical or
chemicalchange,andhow you know-for eachof the 4 investigations.
Due to the needfor GOGGLES, you may wish to wait until week 2 to do this lab, and perhapsdo
Experiment 2, Measurements,first. This allows for an early introduction to metric measurements
in a problem or discussionsectionaccompanyingthe lab-prior to lectureson the topic.
Manual
Laboratory Instructor's
Experiment 2: MEASUREMENTS
Chemicalsneededfor24studentsworkinginpairs:Nochemicalsareneeded
pairof students'
neededfor eachworking
Equipment
I perlabbench
ounces'
H:il':H:"suring cupshowins
* ioo *t; tttt tubes'12each
il;ll iit;
cYlinder
100mL Graduated
,\ ,l2 each
(graduated)'
pipets
10mL Disposable
tllg::*f"J"ffi Jtliil"t.:'J::\"rpiemarkers)'oneperrabbench
Problems
Conversion
Answersto Questions:Chemical
I
2 5 4 cm = 1 3 .3 cm
5 . 2 5i n" -1 ;
2
lL1mmx
lcm
lin'
lo**"
z.sqr*
= 4.92in.
= 262cm1
l4.3cmxl2.Zcmxl 50cm
2 9 -6 mL= 355mL
l 2 . Oo z" -1 ;
ls - = ooo25g
s 2.5mg
" ,ffi--^,
tOOO*g_= 24OOmg
lday
2.40g ldol x- tg
6
POST-LABQUIZ
Answersto PRE-LAB or
1.
2.
3.
4
5.
6
i
length
volume
volume
mass
6.'7cm
0.o25g
176ovd
lm
26.2milesx';rTffiyd
-^ lkm =42.lkm
tooo,
Laboratory Instructor's Manual
Experiment3: DENSITY
Chemicalsneededfor 24 studentsworking in pairs.
Part 1. Densityof a metal
Metal samplesfor densities(about 0.5 cm x 3 to 4 cm) eachidentifiedby an engravednumberor
letter. Metals for suggesteduse includethe following:
Metal
Density
Aluminum
2.7
Cadmium
8.7
Lead
I L4
Densitiesare in g.lcmt
Densit-v
Metal
1.7
Magnesium
8.9
Nickel
7.8
Steel(iron)
Densit_v
Metal
7.3
Tin
9.8
Wood's metal
Znc
7.1
Part 2'. Densityof a liquid, pycnometermethod
Solutionsof NaCl in 8 oz dropper bottles are the unknowns. Each bottle is numbered,but the
concentrationis not to be given on the label.
UNKNOWNS
Unknown
number Concentration
|
4% NaCl
2
8% NaCl
3
12% NaCl
4
16% NaCl
ADDITIONAL LINKNOWNS
Unknown
number
Concentration
6% NaCl
5
6
l0% NaCl
1l% NaCl
7
14% NaCl
8
Part 3: Densityof a liquid, graphingmethod
Four solutionsof NaCl in 8 oz dropper bottles for use by each working pair with 4Yoto 160/o
ConcentrationsSHOWN on the labels. Unknownsfor Part 3 canbe unknown numbers5,6,7,
and8-the sameonesusedin Part2-or new numberssuchas 15, 16,17 and 18.
Concentration
4% NaCl
8% NaCl
lZYoNaCl
1 6 %N a C l
Unknown
Number
5 15
6 16
7 17
8 18
Concentration
Of the unknown
6% NaCl
l0% NaCl
I l% NaCl
1 4 %N a C l
For variety, and to keep studentsfrom trying to figure out "the code," I often label another set of
the same"unknown" solutionswith ten or twenty addedto eachnumber,giving a set of unknown
n u m b e rssu c ha s 1 5 , 1 6 , 1 7 ,a n d 1 8 .
4
Laboratory Instructor's Manual
Equipmentneededfor eachworking pair of students.
Part 2. l0 mL pycnometer
Part 3. l0 mL graduatedcylinder
25 ft{- (or 20 mL) graduatedcylinder
150 mL beaker
Answersto Questions. Densityproblems
I a 7.10 cm3
I b. yes, the metalcouldbe zinc.
2aY:
2b
mlD
336L
t s6mr
t/
rQto
Answersto PRE-LABor pOST-LABeUIZ
1. mass,volume
2 0 666 glnL
a
J.
9 2 . 0g
4
Partially fill a graduatedcylinder with water and write down the precisevolume.
Carefully,
put the irregularobject in the graduatedcylinderand write down the new
volume. Subtractto
obtain the volume of the solid sample. (Note: The volume of the solid
is obtained by
DIFFERENCE.)
Inb oratorv Instructor's Manual
Experiment 4: QUANTITATwE
SEPARATION OF A MIXTURE
Chemicalsneededfor 24 studentsworking in pairs.
Each studentneedsabout 4 s.of a salt and sandmixture labeledas follows:
Unknown
Number
1 (A)
2 (B)
3. (C)
4 (D)
Mixture composition,sameas PERCENTAGES
28.0 g NaCl + 72.0g white sand
23.0 gNaCl + 77.0 g white sand
35.0g NaCl + 65.0g whitesand
40.0 g NaCl + 60.0 g white sand
Equipmentneededfor eachworking pair of students.
150mL Beaker
250 mL Beaker
Evaporatingdish
Filter funnel
Filterpaper,WhatmanNo. 1, 1l cm diameter
100 mL Graduatedcylinder
Heat lamp with clamp(or drying oven at I lO"C)
Ringstandand large ring
Small ring for funnel
Stirring rod
Washbottle
Watch glass
Wire guaze
Answersto Questions:A Mixture Problem
3.84g sample
1.43g sand
2.41 g sugar
2.419sugar/3.84gsamplex l00o/o: 62.8Yotablesugar
Answersto PRE-LAB or POST-LAB QUZ
1 Q.6a g sand)/ (5.2 g mixture)
69.5Yosand
2. 100.0%- 69.5%: 30.5o/osalt (by difference)
3. a, a physicalchange
4. The FILTRATE is the liquid that goesthrough the filter paper. (It containsany solidsthat are
dissolved.)
6
Laboratory Instructor's Manual
Experiment 5: MELTING
POINT, A CHARACTERISTIC
PROPERTY
For this experiment,2 to 3 liters of cooking oil will be needed. The cooking oil should be
returnedat the end of the experimentto be recycled. (If anothergroup of studentsis going to do
this sameexperimentduring the following laboratoryperiod,additionalcooking oil will be needed
becausethe oil needstime to cool beforebeingusedagain.)
Each studentneedsa lew crystalsof one of the following unknowns dispensedfrom a mediumsizetest tube by the instructoronto the student'swatch glass.
Unknown
A
B
C
D
E
F
G
H
I
J
K
Chemical
benzophenone
bibenzyl
6-chlorothymol
palmiticacid
acetanilide
vanillin
d,l-mandelicacid
benzoicacid
trqns-cinnamic
acid
cholesterol
anthranilicacid
M.P. oC iTot:\,/-av,zccl
48-50
50-51
58-59
-'.,r w 'l
6l-63 - ,Onl.r,.r
79-81
8l-83 - t)rKncw'r tr I
119-121
l2l-122 133-135
144-146-'t)r\(rro"'r * L
146-148
Equipmentneededfor eachworking pair of students.
250 nL Beaker
Melting point tubes(closedend capillarytubes)about 2 mm x 8 cm
Rubberrings,3 mm wide (about 1/8 in.) cut from t/cinchamberlatex tubing to hold the
meltingpoint tube next to the bulb of the thermometer
Ringstand,wire guaze, and large ring
Stining rod
200'C Thermometer
Thermometerclamp (or small 3-prong clamp,or cork drilled for thermometerand split down the
sideso it can be held by a utility clamp)
Answersto PRE-LAB or POST-LAB QLIZ
L Melting point is
(a) a physicalproperty ofa substance.
Z. The meltingpoint or rangeof an impurecompoundis
(c) lower than the meltingpoint of the pure compound.
Laboratory Instructor's Manual
Experiment 6: CHROMATOGRAPHY
Chemicalsneededfor 24 studentsworking in pairs.
\
0.25M NaOH in 7 oz plasticdropperbottles,one per lab bench
,
l% Dimethylglyoximesolutionin I oz plasticdropperbottles,one per lab bench
Acetone,500 mL total per lab, or I acetonesqueezebottle per lab bench
12M Hydrochloricacid, 150mL total per lab, or I smallbottleper lab bench
Distilled (deionized)witer in squeezebottles,one bottle per lab bench
Six developing chambersmade from 1000 mL TALL FORM LIPLESS beakers distributed
throughout the lab in the fume hoods. In each developingchamberplace a 100 mL beaker of
concentratedaqueous ammonia surroundedby a ring of glass marblesto hold the beaker of
ammoniain place. Set a watch glasswith ridges on top of eachbeakerof ammonia. Theremust
be enoughroom above this assemblyto set the rolled up chromatogramfor developing. A glass
petri dish works nicely as a lid for eachchamber.
The following "knowns" can be provided in 2 oz squarebottles, one set per lab bench,with a
capillarytube in eachbottle for spotting.
2M
2M
2M
2M
2M
Manganese(ll)nitrate
Iron(III) nitrate
Cobalt(Il) nitrate
Nickel(Il) nitrate
Copper(Il) nitrate
UNKNOWNS contain I to 4 of the following ions. Mn2*,Fer*, Co2*,Ni2r, Cur*
Number
or Letter
1L
20
3P
.
4Q
5D
6C
7A
8K
Ions presentin mixture
Ni2*, cu2*
Mn2*, Fg3n
Fe'*, Ni2*
Fe3*,co2*
Mn2*,Fe3*,co2*
2 Fe3*. Ni2*, Cu2*
Fe3*,co2*, Ni2t,cu2*
Fet*, co'*, Ni2*
Number/Letter Ions Present
in mixture
g z
Mn2*, Co2*,Ni2*, cu2*
lo I
Co2*,Ni2*',Cu2n
II F
Mn2*, Co2*,Cu2n
12 J a
Mn2", Fd: Ni2*
13 B
Mn2*.Cu2*
14 P
Fe3t,,Ni2*
15 K
Fe3*,Co2*,Ni2*
16 F
-t.Mn2*, Co2*,Cu2*
Equipmentneededfor eachworking pair of students.
I Pieceof WhatmanNo. I chromatographypaper,20.0 cm x 10.0cm. Individual piecesthis
size-each working pair gets one-should be cut in advancefrom large sheetsof
the chromatographypaper. Piecesthis sizefit thesebeakers.
Double-tippedQ-tips, severalplacedin a r 00 mL beakeron eachlab bench
Capillarytubesfor spottingunknowns
Six-inchplasticruler
8
laboratory Instructor,sManual
600 mL tall form liplessbeakerto be usedas a developingchamber
A cover for eachdevelopingchamberhavingan appropriatesize,suchas a glasspetri dish,or a
glasssquare.
100 mL (or 50mL) graduatedcylinder
Glassstirringrod
2 Staplers
Infraredheatlamp bulb with clamp,for drying chromatograms
Answersto PRE-LAB or POST-LAB QUV
l. The type of chromatographyusedin this experimentis
(d) paperchromatography.
2. The distanced (smallletter) representsthe distancefrom the original spotting line to the
(b) centerofthe final spot.
3
The distanceD (capitalletter) representsthe distancefrom the original spottingline to the
(d) solventfront.
4 . R r = 3 . 2 c m / 8 . 2 c m: 0 . 3 9
LaboratoryInstructor's Manual
Experiment 7: MOLAR MASSES OF SOME GASES
Chemicalsneededfor 24 studentsworking in pairs.
The following compressedgaseswork nicelywhen dispensedfrom large cylindersstandingon the
floor (and securedto a bench for safety)with two-stage regulatorsset to dispensethe gas at a
pressureof about l0 psi. Connectabout three feet of amberlatex hoseto eachregulator. Have
studentsput the hoseto the bottom of the bottle while counting out l0-l I secondsand cap it.
Large tanksofoxygen, argon, and carbondioxideare suggested.
Small disposabletanks of propane gas with no regulators, but fitted with a short hose, are
satisfactory.Thesetanks can, in fact, be set upright insidea fume hood.
Equipmentneededlor eachworking pair of students.
500 mL Polyethyleneplastic bottle with tight-fitting screw cap, the more rigid the better, so
studentswill be lesslikely to squeezethem and,thus, changetheir volumes.
200 mL or 500 mL graduatedcylinders,2 per lab bench
Answersto PRE LAB or POST-LAB QUV
l. Gasescollectedwhenthe bottleis heldupsidedown.
Natural gas
Helium
2.
fill the bottle with tap water
(a) to overflowing and measurethis volume with a graduatedcylinder.
3. In this experiment,molar massesare basedon
(b) oxygen gas as a standard
l0
Laboratory Instructor's Manual
Experiment 8: ATOMS
AND SPECTRA
Chemicalsneededfor 24 studentsworking in pairs.
Part B, gas spectra,and Part C, cation spectra(flame tests),can be performedas demonstrations
by the laboratoryinstructor as each studentusesa hand-heldspectroscopein a darkenedroom,
but many instructors prefer to set up one station for studentsto observeeach spectraso that
studentsmove from one station to the next in a musical chairs type of arrangement. Both
approachescan be usedeffectively;the choiceis yours.
Chemicalsneededfor Part C, cation spectra,are listed here. Each chemicalcan be in a small
plastic vial, labeled,and used with a nichromewire attachedto the end of a stick for a handle.
Chemicalslisted here are in the order shown in the data table of the laboratorymanual.
L
2.
3.
4.
lithium chloride
sodiumchloride
potassiumchloride
strontiumchloride
5. calciumciloride
6. cupricchloride
7. unknown:sodiumbicarbonate.
etc
Equipmentneededfor the entireclassset up.
Part A:A demonstrationthat requiresa Crookes tube with a horse-shoemagnet or bar magnet
and a high voltageTeslacoil (or a battery with a coil).
Part B:Gas dischargetubesand high voltage power suppliesfor dischargetubeswith clips to hold
each tube. Thesecan be set up as a classdemonstrationin a darkenedlaboratory with
each studentusing a simplecardboarddiffractiongrating hand-heldspectroscope,or with
stations set up around the laboratory where studentsview each gas spectra using a
stationaryspectroscope.
The gas dischargetubes selectedfor use here have the most colorful spectra or are
significantfor other reasons.
l. mercury (nice, bright spectra. Point out that fluorescentlights have these same lines
becausethey containmercuryvapor.)
2. helium (elementdiscoveredby its spectrum,seethe textbook)
3. neon (the gas in neon signs)
4. argon (usedin welding)
5. krypton (For a little fun, remind students that Super Man was only vulnerable to
"kryptonite.")
6. oxygen(its linesare not strong)
7. hydrogen(Questionstudentsas to why an elementwith only 1 electroncan have 3 linesin
its spectra. Then, point out that electronsin atoms are in energy levels. Exciting the
electronsby, for example,heat (IR), light (UV), electronbombardment(Tesla coil), or a
chemical reaction (chemical light sticks) causeselectronsin atoms to jump to higher
energy levels as energy is absorbed. The spectrumis observedonly when EXCITED
electrons fall back to their ground (most stable) state. Visible light is emitted when
LaboratoryInstructor'sManual
11
electrons fall back to their second energy level. Thus, as describedby Niels Bohr,
electronsin atoms are not distributedin a randomfashionbut. rather. are in what we call
disreteenergylevels fBohr calledthem shells]. Seethe text.)
Part C:Flame test set up with hand-heldstudent(cardboard)spectroscopes
or a larger,stationary
spectroscopeat each station. Use a nichromewire insertedin the end of a pencil-size
pieceof balsawood-or equivalent-as a handleto hold each5-cm (2-inch) pieceof wire.
Solid chemicalsdropped into Bunsen burnersover severalsemesterswill causethem to
corrode, but small amounts of concentratedsolutions of the salts can also be used
effectively.
PartD:Use a wall chart or an overheadprojector transparencyof the electromagneticspectrum
like the one includedin the studentlaboratorymanualto point out the various regionsof
the spectrum,the type of radiationinvolved,and the energysourcefor each.
Part E: Thesedemonstrationscan be perlormedby the instructor.
Use a hand-heldultraviolet lamp with W-A and UV-B rangesand show the effectsof
IIV-A and -B light on differentrock samples.Someglow more brightly in one than in
the other, so the instructor can point out that electronsjump to higher energylevels
only when sufficient energy is applied. As another example,comparethe effects of
[IV-A and UV-B radiationon an aqueousfluorescinesolution in a clear glassbottle,
such as a medicinebottle. (The bottle is convenientbecauseit can be storedeasily'for
usethe following semester.)
Have a studenthold one hand near the IIV lamp and report the intensity of the heat (IR
radiation). Also observewhite cloth-a white shirt-under UV light for a measureof visible
light intensity.
Use a 40 W incandescentbulb in a simplereflector to demonstratea qualitativeheat (IR
radiation)measurementby having a studenthold a hand near the bulb. Also observe
shitecloth-a white shirt-under the light bulb for a measureof visiblelight intensity.
Use a heat lamp to demonstratea qualitativeheat (IR radiation)measurementby havinga
studenthold a hand nearthe hot plate. Also observethe effect on white cloth brought
nearthe heatplate for a measureof any visiblelight. Seebelow.*
Use a hot plate to demonstratea qualitativeheat (IR radiation)measurementby havinga
student hold a hand near the hot plate. Also observethe effect-if any-on white
cloth brought nearthe hot plate for a measureof any visiblelight.
*Point out that the heat lamp emits significantamountsof both visible and IR radiation.
The 40 W bulb also puts out both visible and IR radiation, but the proportionsare
different. While a 40 W fluorescentbulb is cool to the touch and is reportedto be
about l0% efficient,a 40 W incandescent
bulb is warm to the touch and is only about
5%oefficient-so it's mostlva"heat bulb."
l2
Laboratory Instructor's Manual
Answersto Questions: Atoms and Spectra
l. Line spectrais quite useful in chemicalanalysisbecausethe line spectrumof each elementis
quite differentfrom that of everyother element,and can be usedto identiff what elementsare
present,regardlessof what other elementsmay also be presentin a compoundor in a mixture.
2. The discrete lines in a line spectraindicate, as explainedby Bohr, that electrons exist in
definite energy levels. Electronsthat fall from a higher energy state to a lower state emit
energywith definitefrequenciesand, for frequenciesof visiblelight, we observecharacteristic
colors. A continuousspectrumwould be observedonly if there were no energylevels.
3. W radiationhasenergythat is a little higherthan that of visiblelight.
4. IR radiationhas energythat is a little lower than that of visiblelight.
5. The longestvisiblewavelength: red. The shortestvisiblewavelength:violet.
The highestfrequency: violet. The greatestenergy: violet.
6. Objects-including certainrocks-that glow in UV light, absorbthe high energyUV radiation
which excites electronsand, if the excited electronsfall back to their ground stateswhile
emitting frequenciesthat correspondto visible light, producevisible colors. (This can occur
when excitedelectronsfall backto the secondenergylevel of the atom.)
7. Objectscan be seenunder a heat lamp becausethe lamp emits both visible light and infrared
radiation(heat).
Answersto PRELAB or POST-LAB QUIZ
l. Picturesof individualatoms
(c) were first seenin 1970
2. ...colorof visiblelight...longest
wavelength
(d) red
3. ...longestwavelengths
(e) IR
4. "black light" is
(a)w
5. Heat (IR), light (vis), electronbombardment(highvoltage),and chemicalreactions(not shown).
Laboratory Instructor's Manual
IJ
Experiment 9: CONDUCTIVITY AND SOLUBILITY PROPERTES
A videotapeof this demonstration-one that is not of professionalquality-can be obtainedby
contactingthe author of this laboratorymanual(seeExperiment 13 in this manual),but you may
prefer to make your own. Using a video projector allows the student to view large close-up
imagesof the chemicalsbeing tested.
Chemicalsneededfor this LABORATORY DEMONSTRATION
Use 100-mLlabeledbeakers,eachfilled to a depthof about 2to3cm with one of the following
chemicalsfor electricalconductivitytesting.
1. potassiumnitrate,solid
2. potassiumnitrate,0.1 M aqueous
3. potassiumnitrate,solid, in cruciblesupportedby a triangle?rndsupportring for meltingwith a
Bunsenburner.
4. sodiumchloride,solid
5. sodiumchloride,0.1 M aqueous
6. table sugar,solid
7. tablesugar,aqueous
8. table sugar,solid,in cruciblesupportedby a triangleand ring. Heat with a Bunsenburner.
9. ethanol
10.benzene
I I distilledwater
12. tap water
12.toluene
I 4. carbontetrachloride
15.distilledwater * benzene(immisciblelayers)
16.previousmixture + HCI gas (Check conductivityof the lower aqueouslayer)
17.previousmixture + HC I gas (Check conductivityof the upperbenzenelayer)
I 8. aceticacid, glacial(concentrated)
19.aceticacid,0.l M
In medium-sizetest tubes,mix the following liquids, observewhether the liquids are miscibleor
'immiscible,
and conclude whether the bonding of the SECOND member of the pair is polar,
intermediatein polarity,or nonpolar.
20. water * benzene
21. water + diethyl ether
22. water * carbontetrachloride
23 carbontetrachloride* acetone
24. water * acetone
Equipmentneededfor the demonstration.
A nice conductivitytesterfor usewith I l0V AC can be preparedby wiring a 0.5 W neon glower
bulb (standardbase,Cenco Scientificor other supply house) in parall'elwith 10 W and 100 W
14
LaboratoryInstructor'sManual
bufbsby assernblingsocketsfor the bulbs in a "T" shapepatternin a socket wired in serieswith
two healy gaugepiecesof No. 12 gauge copperinsulatedelectricalwire used as electrodes.A
conductivityapparatuscan be purchasedfrom a scientificsupplyhouse.
For numbers 16 and 17, use compressedHCI gas or assemblea HCI gas generator. Attach a
separatoryfunnelto a vacuumflask that has a latex rubber hose and a short piece of glasstubing
attachedto its side arm. Dripping concentratedsulfuric acid, slowly, from the separatoryfunnel
into 12 M HCI in the flask liberatesHCI sas.
Answersto PRE-LAB or POST-LAB QUIZ
l.
...bondingin potassiumnitrateis
(a) ionic.
2. Carbontetrachlorideis
(c) a nonconductorof electricity.
3. ...bondingin carbontetrachlorideis
(b) covalent.
4. HCI in benzeneis a (l)_
and in water is a (2)_
(e) NONconductorof electricity. .GOOD conductorof electricity.
5. Water and carbontetrachlorideare (l)_.
(d) immiscible.. .nonpolar.
Carbontetrachloridemoleculesare (2)_.
Laboratory Instructor's Manual
15
Experiment10: MoLECULAR MODELS AND sHApES oF MOLECULES
Chemicalsneededfor this investigation:NONE
Equipmentneededfor this investigation.
,
One set of ball-and-stickmolecularmodelsis neededfor eachstudentor for eachpair
of students,
dependingon the approachprefenedby the laboratoryinstructor.
f
Answersto euestions.Additionalstructures.
I
1. Beryllium
+ 7 +7: l6valenceelectrons.
difluoridehas2
Its Lewis structureis
, r-g"-;
:
Its shapeis rinear.
2. Phosphorous
trichloridehas5 + 7 + 7 + 7 : 26 valenceelectrons.
Its Lewis structureis , cr-p-cr
,
-l
Its shapeis pyramidal.
'9.1'
3. Aluminumtrichloridehas3 + 7 + 7 + 7 : Z4valenceelectrons.
Its Lewisstructure
is ,il,
,cr,
Its shapeis trigonalplanar.
\/
AI
I
: Cl :
Answersto PRE-LAB or pOST-LAB eUIZ
l. A watermoleculehasa -(b) bent(angular)
2. COz has a
(a) linear
shape. Structure:
shape.
3. Methaneand carbontetrachloridehavea
_
(e) tetrahedral
Structure:0: C = 0
ff - O,
I
H
shape
H
Methanestr uctur e.
H
I
C- H
H
4. Ammoniahasa _
(d) trigonalpyramidal
shape.
Structure:
ff - N - H
I
H
l6
Lab oratory I nstructo r's Ma nual
Experiment ll:
THE FORMULA
OF A HYDRATE
Chemicalsneededfor 24 studentsworking in pairs.
Part A:Arrange 4-oz bottles of these chemicals-in order-in a common area with the NAME
(not the formula) shown on eachlabel,and with a scoopulabesideeachbottle. Keep lids
on thesebottles.
o
.
.
bariumchloridedihydrateLABELED AS bariumchloride
sodiumchlorideLABELED AS sodiumchloride
copper(Il) sulfatepentahydrateLABELED AS coppersulfate
Part B: Arrange 4-oz bottles of these chemicals-in order-in a common area with the
FORMULA shown on each label, and with a scoopulabesideeach bottle. Keep lids on
thesebottles
o
.
o
calciumchloride,anhydrous
sodium hydroxide pellets (use a plastic bottle and plastic lid-not
base.)
zinc sulfate heptahydrate
Part C:Unknowns.
glass-for this strong
Number of water
moleculesin hvdrate
BaClz.2HrO
labeledas
BaClz . ? H2O
2
NazCOr. lH2O
labeledas
NazCO:. ? H2O
1
KzCOr. l.5H2O labeledas
K2CO3- ? H2O
1.5
M*SOa'7H2O
labeledas
M'SO4.? H2O
7
NazSO+.l0H2O labeledas
NazSOr. ? H2O
l0
NiSO4' 6H2O
NiSOn. ? HzO
labeledas
6
Becausenickel(Il) sulfatehexahydrateis green (not white) and it cakes in crucibles,it is
not as desirableas an unknown as are the others.
Equipmentneededfor eachworking pair of students.
PartsA and B:
4 smallto mediumsizetest tubes
250 mL beaker
plasticweighingboats (or smallsheetsof paperfrom note pad with cornersfolded up to make
a box.)
LaboratoryInstructor'sManual
tl
Part C:
cruciblewith cover
clay triangle
ceramicpad for cooling the crucible
tonss
Answersto PRE-LAB or POST-LAB QLIZ
I . A substance
that loseswaterwhen heated...is
(b) a hydrate
2. The solidresidue...
(a) an anhydroussalt.
3. An anhydrouscompoundthat will absorbwater...
(b) hygroscopic
4. A compoundthat will losewater spontaneously...
(e) efflorescent.
5. Short answer: When a pea-sizeamountof a hydrateis heatedin a test tube, dropletsof water
collect at the cool, open end of the test tube.
l8
Lab orato ry Ins tructo r's Manua I
Ert
Chemicalsneededfor 24 students
--.rt 12: IONIC
REACTIONS
rking in pairs.
i
Use 500 mL to I L clear plastic or glass bottles that are nearly transparentso the colors of
solicitationscan be viewed easily,but use an amberbottle for silvernitratewhich is light-sensitive.
NOTE. Labelbottles with the CHEMICAL FORMULA (not the name)so studentswho readthe
chemicalname in the laboratory manual must translate each chemical name into a chemical
formula.
Numberthe bottlesconsecutivelywhen they are in alphabeticalorder by FORMLILA' and instruct
studentsthat chemicalsare arrangedin alphabeticalorder by formula. Explain that to find silver
nitrate,for example,look for "Ag: not "S." Placethe samenumberon the bottle cap and the label
so bottlesand capsdon't get mixed up when it is time to storethem away for the next semester.
Line up the bottles of solutionsin alphabeticalorder in severalfume hoods or at the side of the
lab.
Put a disposable
PLASTIC l0 mL pipet (with graduations)in eachbottle.
For a MICROSCALE approach,use a smalldropperbottle of eachchemical.
Use0.1 M solutionsof the followins:
l. AgNO3
6. CoClu
2
7. CuClz
Alz(SOr)r
Ba(NO3)2
5 Ba(OH)z
> \2.
-8. CuSO+
-.3. BaClz
\ 4
\ I l. KzCrOr
)
x
FeCl:
10.KBr
'
,1,
Kzcrzot
'.16. NaOH
\17. NazSOc
I 3 .K I
\a
Nrtqcr
14.Nacl
xl9
NiClz
\s
Nat
'*20
Pb(NO:)z
Equipmentneededfor eachworking pair of students.
6 to l0 smalltesttubes(13 mm x 100 mm)
Appropriatetest tube rack for test tubesof this size
For a MICROSCALE approach,use a plastic well plate with 15 or more wells and use small
polyethylenetransfer pipets (Beral pipets) or medicine droppers to dispense5 drops of each
solution. The wells of the well plate can be cleanedwith water and a Q-tip or a pipe cleanerwith
its end doubledback to avoid scratchingthe plastic.
LaboratoryInstructor's
Manual
19
Answersto PRE-LABorpOST_LAB
etIIZ
l.
Precipitates
form whencompounds
producedhave
(c) a low solubilitv.
2. (a) true
3.
..metathesis
reactions
(d) doublereplacementreactions.
4'
Short answer: DISSOCIATED means
that the ions are separatedfrom one another,
they are
completelydissolvedin water, and they
move aroundindependentlyfrom one another.
5. KCI andBaSOo
6. Completeequarion: AgNO3 +
NaCt -__) Agcl(g
7. Net ionic equation: Ag*(uq) +
Cl-(aq) __-+ AgCl(s)
+ NaNO:
20
Laboratory Instructor's Manual
Experiment 13: TYPES OF CHEMICAL
REACTIONS
Three videotapedprograms showing each of the chemicaldemonstrationsfor Part I (19 min.),
Part II (20 min.), and Part III (30 min.) are availablefrom the author. They are in color, effective,
and havebeenedited,but they are NOT of commercialquality. If you wish to havea copy, send
a PROFESSIONAL quality Vz inch VHS blank videotape to Ralph A. Burns, Chemistry
Department,St. Louis CommunityCollege-Meramec,
I1333 Big Bend Blvd., St. Louis, MO
63122.
Each demonstrationcan be performed live for students,but proper SAFETY PRECAUTIONS
must be followed. Some of the reactantsand products are toxic or are difficult to view by
studentsat a distance. Most of the demonstrations
listed in Parts I to III are describedin one of
the two following sources:
.
o
Bassam Z. Shakhashiri,Chemical DemonstrationsVol. I to 4, The University of
WisconsinPress.
Hubert Alyea, Tested Demonstrations.ACS Division of Chemical Education, (out of
print, but can be found in manychemistrylibraries).
OTTMR VIDEOTAPED CFIEMICAL DEMONSTRATIONS:
Demonstrationsselectedfrom the WORLD OF CHEMISTRY seriesof videotapescan also be
usedhere. The excellentdemonstrations
in this seriesare carriedout by Donald Showalterof the
Universityof Wisconsin,StevensPoint.
Other sourcesof excellentvideotapedchemicalreactionsinclude those from the University of
Illinois performedby Loretta Jonesand StevenZumdahl.
Due to the natureof this lab, no PRE-LAB or POST-LAB QUIZ is includedhere.
LaboratoryInstructor'sManuol
2l
EXPETiMENT
14: THE PREPARATION OF ALUM FROM SCRAP ALUMINUM
NOTE: Studentsfind this experimentto be quite interesting,but it takesa FULL Z-Iv lab,so take
as little time as possible-about 5 to 7 minutesonly-for any prelabexplanation (Do most of the
explaining during the discussionsection.) Also, have studentsstart weighing and cutting the
aluminum foil into small pieces as soon as they come into the laboratory Later, when the
aluminumis reactingwith KOH, is a good time to stop and describepertinentdetails,such as the
use of the Buchner funnel and a warning to boil the original solution down to JUST ABOVE
HALF its originalvolume,or crystalsmay not form.
Chemicalsneededfor 24 studentsworking in pairs.
Note: Bottles of chemicalsplacedon eachlab benchmakesthem convenientand savestime.
I roll of aluminumfoil (eachpair of studentsneedsa pieceabout B x 12 inches)
1.5M potassiumhydroxidesolution(84.0 gL),600 to 700 mL per class.
9.0 M sulfuric acid solution,600 to 700 mL per class.
50oloethanolsolution,150mL per class.
Crushedice in containersat the end of eachlab benchfor coolinethe beakers.
Equipmentneededfor eachworking pair of students.
Hot platesset up IN FUME HooDS (one for every 2 pairs of students.)
250 mL Beaker
250 mL or 500 mL Vacuumflask
Large Buchner funnel with rubber stopper cut to fit stem of funnel and flask
Filter paperto fit Buchnerfunnel
Short stemfunnel
Glassstirring rod, preferablywith a policemantip
100 mL Graduatedcylinder
For the meltingpoint determination:
I Thermometer,100 or 110 oC maximumgraduatedin one degreeintervals
I Melting point capillarytube-closed at one end-per pair of students
I Small rubberbandto hold capillarytube in placeon thermometer(can be cut from t/qinch amber
latex tubing).
100mL Beaker or wide mouth bottle of similar sizeto hold alum sample
Mortar and pestleOR use a watch glassand the roundedend of a largetest tube.
INSTRUCTOR NOTE: The alum hasa melting point of 92 "C.
At the end of the experiment,each student,or working pair of students,should submit: (l) the
alum samplein a wide mouth bottle or a 100 mL beaker,(2) a label listing the 6 items specifiedin
data, and (3) the melting point tube. The student shouldbe able to give the melting point of the
alum sample,the gramsof actualyield, the theoreticalyield, and the p-rcent yield.
Answers to PRE-LAB or POST-LAB eItZ
I
(b) boils down to half the originalvolume
2. Calculation. 19.0g
3. Calculation. 83.2yo
Laboratory Instructor's Manual
22
Experiment 15: GRAVIMETRIC
ANALYSIS
OF A SOLUBLE
SULFATE
Chemicalsneededfor 24 studentsworking in pairs.
12 M Hydroctrloricacid in dropperbottles
0.1 M Bariumchloride,300 to 500 mL
0 30 to 0.35 g solublesulfatesalt "unknown" samplefor eachpair of students
Unknown sulfatesamples
Unknown
number
I
2
3
4
Mixture composition*
Unknownswith sodiumsulfate
12ganhydrousNa2so4+
SgNaCl
+ 13g NaCl
7 ganhydrousNazSO+
l0 g anhydrousNazSO++ 10 g NaCl
l 4 g a n h y d r o u s N a 2 S O a +6 9 N a C l
PERCENT
SULFATE
40.56%
23 66%
33.80Yo
47 320
Unknownswith potassiumsulfate
5
6
7
8
20 g anhydrousK2SO. + 0 g NaCl
l0 g anhydrousKzSOq+ l0 g NaCl
17 g anhydrousK2SOa * 3 g NaCl
13 g anhydrousKzSO++ 7 g NaCl
55.170
27.58%
46.890
35 86yo
*Be sureto thoroughlymix all bottles of unknownsbeforethey are dispensed.There are more
different unknown mixtures listed here than you may need.
Equipmentneededfor eachworking pair of students.
250 mL Beaker
400 mL Beaker
Ceramic pad
Crucibleand cover
Filter funneland support ring
Filter paper,WhatmanNo. 44 ashless,I I cm
Glassstirringrod
100mL Graduatedcvlinder
Labels
Tongs
Clay triangle
Watch glass
Answersto PRE-LAB or POST-LAB QUIZ
l. BaSOa
2. 72.30
LaboratoryInstructor'sManual
23
Experiment 16: THE PRESSURE-VOLUME RELATIONSHIP FOR GASES
A color videotapeof this demonstration-one that is NOT of professionalquality but "does the
job"-can be obtainedby contactingthe author of this laboratorymanual,but you may prefer to
make your own. Using a video projector allows studentsto view large close-up images of
readingstakenfrom the J-tubeapparatus.
Chemicalsneededfor the demonstrationif performedlive.
Mercury
Equipmentneededfor the demonstrationif performedlive.
J-tube(a 5-mm glasstube bent into the shapeof the letter ".l' so that one arm is about 15 cm and
the other arm is about 80 cm long. The short end must be sealedshut.) The apparatuscan be
purchasedfrom a suppliersuchas Cenco.
Assemblea standto hold a meter stick (vertically)and the J-tubewith a sampleof mercury at the
bottom of the tube that hasthe samedepthon both sides.
Attach a funnelto the open end of the J-tubeusing a short piece of tubing.
150 mL beakerto hold the mercury
During the demonstration
:
Take a barometricpressurereading when the levels of mercury on both sidesof the J-tube are
equal. Add mercury with a medicine dropper and take severalnew pressureand volume (of
trappedgas) readings. It is nice to end the investigationwith just enoughmercuryaddedto make
the total pressureexactly DOUBLE the original pressure so one can read the volume, and
"discover"that the volume is cut in half when the pressuredoubles.
Studentsshouldgraph the results. This is an excellentexercisein graphing. Many studentswill
havetrouble with choosinga scaleFIRST and makingthe graph fill the graph paper.
Answersto PRE-LAB or POST-LAB QUIZ
l. ......aspressure
increases
Answer: (b) volume decreases.
2.
gaspressureand volume
Answer: (b) are inverselyproportional.
24
Lab orato ry Ins truc to r's Manua I
Experiment 17: DETERMINATION
OF THE MOLAR
VOLUME
OF A GAS
Chemicalsneededfor EACH LAB BENCH with 4 pairs of student.
12 M Hydrochloricacid, 100mL
WARNING: Concentratedacid
PRECISELY pre-cut5.0 cm stripsof magnesiumribbon,one per pair of students.
Smallpieceof steelwool to removeoxide from the magnesiumribbon.
Fine coppermagnetwire (No. 32 or 36) on a spool. Studentscanuse apair of ordinaryscissors
to cut offabout 12-15inches(30-40cm) of the wire
Equigmentneededfor eachworking pair of students.
2 L Beakeror I gallon batteryjar
Buret clampto hold eudiometertube verticallyin invertedposition
Eudiometer
Rubberstopper,2hole, No. 00 to fit eudiometer
Ruler, plastic,metric 15 cm (6 inch)
Scissors(to cut fine copperwire)
Thermometer
Wallbarometer,mercury
Answersto PRE-LAB or POST-LAB QUIZ
l.
moleor Mg reactsto give
......each
(b) one mole of hydrogengas.
2. ... ..theeudiometermustbe raisedor loweredso the water levelinside...is
(c) in line with the water level outsidethe tube.
3.
The final mathematical
step...
(a) divide liters of gasby molesof gas produced.
4.
The gas pressureinsidethe collectingtube is from
(d) hydrogengasand water vapor.
LaboratoryI nstruclor's ManuaI
Experiment 18: DIFFUSION, THE RACE BETWEEN GASES
Chemicalsneededfor EACH LAB BENCH with 4 pairsof students.
Concentratedammoniasolutionin smallbottles (or dropperbotttes)
ConcentratedHCI in smallbottles (or dropperbottles)
CAUTION: Studentsmust wear eye protection. USE FUME HOODS.
Avoid ammoniumchloride"smoke" in the laboratoryby keeping
excessHCI and ammoniasolutionsto a minimum. Solutions
shouldnot be left uncoveredand out in the open air.
Equipmentneededfor eachworking pair of students
I Glasstube, about 70 to 80 cm long with a diameterof about l0 mm.
I Cotton ball (to be pulled apart to make2 cotton plugs)
I Double buret clamp (to hold the tube LEVEL in a horizontalposition)
Forcepsto hold the cotton plugs
Meter stick
Answersto PRE-LAB or POST-LAB QUIZ
1. The rate at which a gastravelsis
(a) directlyproportionalto the distancetraveled.
2. The distancea gastravelsis
(c) inverselyproportionalto the squareroot of its molarmass.
3. The rate at which a gastravels(or diffirses)is
(c) inverselyproportionalto the squareroot of its molar mass.
4. Which one of the following gaseshasthe greatestrate of diffi.rsion?
(b) Nz
25
26
Laboratory Instructor's Manual
Experiment 19: HEAT OF NEUTRALIZATION
Chemicalsneededfor 24 studentsworking in pairs.
SodiumHydroxide pelletsin 4-oz plasticbottles(basiechemicalbalances)
0 25 M hydrochloric acid,2 L
0 50 M hydrochloricacid, I L
0.50M sodiumhydroxide,lL
Note: When making thesesolutionsfor severallaboratorysections,it may by easierto put the
three solutionsin largepolyethyleneplasticjugs with a hosefitting and a hosewith clamp
attachedat the bottom for dispensingthe liquids into graduatedcylinders.
Equipmentneededfor eachworking pair of students.
2 Styrofoamcoffee cups stackedtogetheras a calorimeter
I Lid madefrom a cardboardsquareor anothercup trimmed I cm from the top and turned upside
down into the other two styrofoamcups. Punchholesfor the thermometerandthe stirrer.
I Thermometerwith graduationsin 0.1 oC
I Stirrerfrom insulatedcopperwire (or use a glassrod)
Answersto Questions:
l. Net ionic equationsfor
Reaction1. NaOH(s) ---) Na*(aq) + OfL
Reaction2: NaOH(s) + H*(uq) ---+ HzO + Na+(aq)
Reaction3. Na*(aq) + OHlafl
+ H*(uq) -
HzO + Na+(aq)
2. The heatliberatedfor Reaction2 resultsfrom two processes:
(l) the heat of solutionof NaOH(s), and
(2) the heat of neutralizationfor the NaOH and HCI solutions.
The heatliberatedfor Reaction3 resultsonly from the heat of neutralizationfor the NaOH
andHCI solutions.
3. The E)GERIMENTAL VALUE of the energychange(AH) for Reaction2 is roughly equalto
the sum of the energy changesfor Reaction I plus Reaction 3. This is becauseReaction2
involves the two processesthat occur separatelyin ReactionsI and 3. Some experimental
error is expected.
4. Calculationbasedon studentresults.
5. (a) Using4.0 g of NaOH insteadof 1.6g NaOH would liberate4 O/1.6:2.5 timesas much
heatenergy. Therefore,the numberof caloriesreleasedwould be 2.5 time as many.
(b) Increasingthe quantityofNaOH would NOT affect the total amountof heatreleasedper
mole. When the numberof molesincreasesby a factor of 2.5, the heatreleasedalso
increasesby the samefactor (2.5).
LaboratoryInstructor's ManuaI
Answersto PRE-LAB or POST-LAB QI-IZ
l.
...neutralization
of sodiumhydroxidesolutionby hydrochloricacid is...
(b) equationB.
2. Heat releasedwhensolid sodiumhydroxideis dissolvedis represented
by
(a) equationA.
3. Heat releasedwhen sodiumhydroxideis both dissolvedand neutralizedis..
(c) equationC.
27
7
28
Laboratorv Ins tructor's Manual
Experiment 20: HEAT OF SOLUTION
NOTE: This experimentdoesnot take a lot of time. It canbe done during the same2-hour
laboratorysessionusedfor Experiment19. AlthoughExperimentl9 hasno unknown,
this experimentdoesallow for separateunknownsto be given to eachworking pair of
students.
Equipmentneededfor eachworking pair of students.
Note. This is the sameset of equipmentneededfor Experiment19.
2 Styrofoamcoffeecups stackedtogetheras a calorimeter
I Lid madefrom a cardboardsquareor anothercup trimmed I cm from the top and turned upside
down into the other two styrofoamcups. Punchholesfor the thermometerand the stirrer.
I Thermometerwith graduationsin 0.1 'C
I Stirrerfrom insulatedcopperwire (or use a glassrod)
Chemicalsneededfor 24 studentsworking in pairs.
Eachworking pair willneed 5 gramsof one of the following chemicalsprovided in 4 or 8 ounce
bottleslabeledby unknown numbers.
Unknown
number
Chemical
I
N}I4NO3
2
Heat of solution
calls.
Heat of solution*
callmol
76 callg
6100 calimol
CaCl,
-160 caUs
-18000callmol
3
KNO3
82 caUg
8300 caVmol
4
NazCOz
-53 cal/g
-5600 callmol
5
NaNO:
58 calig
4900 callmol
*The heatof solutiongivenin caVmolisprovidedherebut is not needed.
Answersto PRE-LAB or POST-LAB QUIZ
l. The amountof heatabsorbedby the calorimeteris
(b) the sum of heat absorbedby the water andby the chemicalbeing dissolved.
2. The amountof heat absorbedby the calorimeterand contentsis
(a) equalin value-but oppositein sign-to the heat lost by the chemicalbeingdissolved.
3. If the heat of solutionfor a chemicalwas 22,000caVgwhen 2.0 g of solid was dissolved,the
valuefor the heat of solutionusing4.0 g shouldbe (b) 22,000caUg
Labora tory Ins truc to r's Manua I
29
Experiment 2l: PERCENTAGE OF ACETIC ACID IN VINEGAR
Chemicabneededfor 24 studentsworking pairs.
Vinegar(or 5.}Yoaceticacid labeledas vinegar)dispensedfrom 3 or 4 buretsin fume hoodsor in
the commonchemicalsarea.
0.5000M standardNaOH
Distilled (deionized)water in squeezetype washbottles
Phenolphthalein
solutionin smalldropperbottles
Equipmentneededfor eachworking pair of students.
50mL buret, I per working pair of students
125 rrrL or 250 mL Erlenmeverflask
100mL Beaker
250 ntL Beaker
Answersto PRE-LAB or POST-LAB QUIZ
1. The processof carryingout an analysiswhere...
(d) a titration.
2. ...thepoint at which the indicatorchangescolor is called
(c) the end point
3. In this experiment,one mole of baseneutralizes
(b) one mole of acid
4. Baseis added...until
the solutionin the flaskturnsfrom
(c) colorlessto the first tinge of pink that doesnot go away when swirled.
5. Name: aceticacid
Formula: CH?COOH
7
30
Laboratory Ins tructor's Manual
ACIDS, BASES, AND pH
Experiment22:
Chemicalsneededfor 24 studentsworking in pairs.
PartsA and B:
t headofred cabbage
distilled(deionized)water
100mLeach,of solutionswith pH values0, 1,2,3... to 14
Part C.
Samplesfor pH test, suchas tap water, vinegar,householdammonia,fruit juices,
shampoos/conditioners,
dilutedlaundrydetergents,etc. can be brought from home by students
Part D.
175 mL Buffer solutionwith a pH of 7.0 (commerciallyprepared)
50 mL 0. 1 M HCI in dropperbottlesfor eachlab benchor 4 pairsof students
50 mL 0.1 M NaOH in dropperbottlesfor eachlab benchor 4 pairsof students
Wide rangepH indicatortest stripsfor eachlab benchor 4 pairsof students
SpecialEquipment
I pH meter (usedby the instructoris neededper lab)
Equipmentneededfor eachworking pair of students.
40 mL beaker
hot plate
+ 5 for samples)
20 smalltesttubesabout l3 mm x 100 mm (15 for the standards
Appropriatetest tube racksfor test tubesof this size
2 medicinedroppers
Answersto PRE-LAB or POST-LAB QttIZ
l. A mixture of weak acid and its salt or a weak baseand its salt is requiredfor a(n)
(b) buffer
A solutionwith a pH of 6.6is
(b) slightlyacidic
A solutionhavinga pH of 9 4 is
(a)lessacidic
thanone havinga pH of 8.2
I
I
I
I
l,
Laboratory Instructor,sManual
3l
Experiment 23: MOLECULAR MODELS: GETTING THE ANGLE
oN cARBoN
Chemicalsneededfor this investigation:NONE
Equipmentneededfor this investigation.
One set of ball-and-stickmolecularmodelsis neededfor eachstudentor for
eachpair of students,
dependingon the approachpreferredby the laboratoryinstructor.
The instructormay have studentswork totally independently,
or may preferto direct studentsas
they CONSTRUCT eachmodel and discussits structuralformula and whether
the compoundis
polar or nonpolar.
Answersto PRE-LAB or pOST-LAB eUIZ
l. In carbon-containing
compoundshavingonly singlebonds,there are always
(d) 4 bondsin a tetrahedralarrangement.
2. Moleculeslike....thathavethe samechemicalformulaare called
(b) isomers.
3. To representa doublebond with ball-and-stick
modersuse
(c) 2 springsbent to connect2 ,.atoms.,'
4. The two structuresshown [where eachcarbonhas2 cl and 2Hatoms]
(a) representthe SAME substance.
3:
Laboratory Instructor's Manual
Experiment 24: ASprRrN AND orl
oF WTNTERGREEN
Chemicalsneededfor 24 studentsworking in pairs.
For aspirin:
75 g Salicylicacid
75 mL aceticanhydride
18 M (concentrated)Surfuricacid in dropper
bottres,75 drops
Distilled(deionized)water in squeezebottles
Crushedor flake ice
l%oFerncchloride
optional: A few commercialaspirintablets
to test with ferric chloride.
ogtof wintergreen: A very short experiment,
not quantitative
f9r
l5 g Salicylicacid
150mL Methanol
1! M (concentrated)H2SO4in dropperbottles
lYoFeric chloride
For aspirin:
100mL Beakeror plasticweighingboat
400mL Beaker
125mL Erlenmeyerflask
5 mL or 10 mL graduated
cylinder
Glassrod
Filterpaper,WhatmanNo. I to fit Buchnerfunnel
Buchnerfilter funner,with rubberstopperto fit vacuum
flask
250mL or 500mL Vacuumflask
Hot platesor Bunsenburners
Rubberhoseto connectBuchnerfunnerto aspirator
on waterfaucet
Scoopula
Small(13 x 100mm)testtube
not quantitative
f91 oil of wintergreen. A veryshortexperiment,
100mL Beakeror plasticweighingboat
400mL Beaker
50 mL Erlenmeyerflask
l0 mL graduated
cylinder
Glassrod
Tongs
Answersto PRE-LABor pOST_LAB
eUIZ
I Thechemicalnamefor aspirin.Acetylsalicylic
acid
2' Thechemicalname_
for oil of wintergreen:Methyrsaricyrate
3. Both aspirinandoil of wintergreen
ire crassified
as (e) esters
4' "'If the sample
turnsdarkpurplewheniron(IrD
chlorideis applied...the
sample
(d) is not pure..
ISBN0-13-013?27-1
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