Wh i le working in the lab, yO U will usc a number of reagents, giving ample chance for exposure to the harmful effects of chem i cals.. These precautions provide protection from spilled
Trang 1like skill in sports, m u sic or art-docs not
come naturally to anybody uccess in each of thcse
a r eas depe n s on discip l ine, prac ti ce and tra i nin ' In
• Alwa ys wor k with instructor sup e rvi s ion Neve r w o r k
in a lab alone
Iwa ys wear goggle s in the lab even ov I' eyeg la sse s: replace
co ntact l e ses \\ ith e y g l ass e s
(ontoct lenses can absorb solvent vapors If you do accidentally get chemicals in your eye, the contact lens can actually trap harmful chemi
cals between the lens and your cornea
Wh i le working in the lab, yO U will usc a number of reagents, giving ample chance for exposure to the harmful effects of chem i cals I n some cases, expos ure will be due
to an acc i denta l spi ll ur breakage of equ ipmcnt Other lim ite ex posure may come as a result of using the chemicals
as directed If yo u can smell a vo t atile chemica l , it could hal-m you Your scnse ofsmel l is very sensitive rcfkcting your body's scnsitiv ity to a ll types of odors Thi s also reflects the eff i ciency of our biochemistry and explains why we have adverse r eactions t o minute quant ities of cer tain chcmicals
the chemi stry lab, you encounter ncw equ ipmen t a
varied types of chemical materia l s, re q ui ring
you plan to usc them safel
Remcmber, details arc importan t in c emistry
not just where numbers a d c a lc ulat io s ar c co n ern
Chemical names and formu l as present a w ho
li ngo You have to kn o w these symbols and
t ions to wOI'k i n t h e l
One leller can mean a lot-chlorine, with on "n," is a toxic
~sodium chloride, with a "d," is a harmless soil
Safety Training
Safety is an integral part of work ing in the chcmis t ry
lab, and a respo ns i bility shareo by studen t s a d
instructors
Learning about safety is part of yo u r ed ucat io n; skil ls
you gain in the lab will serve you i n future careers
and in lifc lf nothing else, they will ma~e you a
better cook'
Be Prepared
Where is the lab exit? l: very lab sho uld have ill
least two exits Know ho w to g et ou t q ui ckly in an
emergency
Never work in on isolated "corner" of a lob; upper-floor
Where is thc n earest p ho nc
may neeo fo call for em
help I f so, di al i l l
local cmergency
• Where is the fume hood? - You 'll
necd to use it for any no,xious reagent
Always use a hood when working with concentrated
acids or aqueous ammonia If Ihe chemical has a pungent order,
or is a health risk, you need to use a hood
Where arc the eyewash sta tion and safety shower?
These arc for wash i ng s~in a nd/or eyes ex posed to
c emicals
• Where is the fil'c extin!! u is h er? You may need to u~ e it
to do use small fires Check with your instruc t or on
guidelines for using an exting uisher So m e fires
require special treatment
Sodium reacts with water, a common ingredient in
most fire extinguishers
Personal Responsibility
R u le I: Protect yourseln Your mistakes will likely harm
you more than a yon e else
Rule 2 : Reael the lab manual be lore class Come to lab pre
pared to work on the assigned ex periment
R u le 3: Always pay atte nt i on as yo u work Wa t ch o t her
students; you ar impacted by their mistakes
Rule 4: Clean up your own mess Y ou arc a partner in
ma i ntaining a sa f e lab
K e vs t o a Clean Lab
Keep your wo rk s p ace c l ea n a d organi zed
Wash labware wit h d tergent: ri n se w i th de- io n i7ed or
disti lled water; usc a was h bottle to conserve water;
drain excess liquid; a l low obje ct t o d ry b e r e stori n g
• Shared eq ui pment wash before and af t er
each use
• After each lab se s ion, return reagents and
eq ui pme n t to the des i gna t ed storage are a s
So, switch to glosses for lob sessions
• W ea r an apron , lab c oa t and g lov es t o limit your ch e mi ca l e xp o s ur e and t o s av e c lothin g from
ch ; mic a l s tain s
Select gloves to match the chemicals that you are using in the lob Some gloves dissolve in certain organic solvents Think about what happens when you expose a Styrofoam cup 10 ace
tone Unless you wont it stained, never wear your favorite new shirt to the lob
• We ar closed-to e sho es a nd long pants t o protect yo ur Icct and l egs
These precautions provide protection from spilled chemicals and broken gloss
• T i c back hair an d a void bulk y s leeve s th a t II1tcr fe r e i th wor k
You also may wont to remove rings and other distraclingJ'ewelry that may lessen your grip on beakers, test tubes on other equipment Some jewelry may be damaged by lob chemicals
Do not store book bogs, cell phones or other electronic gear on the lob bench They can interfere with your work space and could be damaged by a chemical spill or occident
Foo d a nd dr ink sh oul d not be brou g ht in t o th e lab
This greatly enhances the chance that you will accidentally consume lob chemicals along with Ihe drink or snack,
Wa s h your hand s ali e r each lab sess ion bcfi) r c l e avin g
This will greatly reduce your risk of harmful exposure to chemicals You definitely do not wont to have lob chemicals flavoring the burger and potato chips you have after lob!
U~ c to ngs to handle la b w a rc whil e i t i s hca t cd by a
b rn e r o r hotpl a t e All o w t h e item t o coo l t o roo m tem p er aturc b efor e w e i g hin g
Hot lob items do not look hal ,
alter the reading of a balance
Liq id Reagent
C o ver th e b e ker wit h watch t!l ass
Us e "bo ilin g s t o es' t o pr o m ow s m oot h bo ilin g Flam ma ble s olwnt : Ta k e c are when h atin g \\ i th a h t
pl ate; avo id u sc of ga s burn e r
H a ndle t es t tu b e \ \ i th wire-hold er Heating a liquid is not a race; overly rapid heating can couse the solution to erupt into a boil, termed bumping, usually resulting
in the liquid spilling onto the hot plate or burner and the lob bench top, and soaking your notebook, etc
chcmical c-.posure Call emergency personnel for
Us e a w eigh ll1 di,h on the medical treatments for burns balan
C ove r the di s h t o
l o s s sp ill s o r contam inati oll Good lab planning and prevcntion of accidents is the bcst
fi rst aid Do not b e hcmic! Dcal \\ ith c uts and minor Always record lob data in on
organized notebook, including anything that is major.
the number and unit
Possible Risks of Exposure
I nha l ing chcmica l rowdcr or vapor Takc care when working with any vola l e solvents
Remember, if you can smell it, it could be harming you
I ngesting so lid o r liquid chcmicals by mouth You are not likely to make a meal of chemicals in the lob, but any chemical on your hands or face could end up inside you when you consume food after the lob session
Punctur i ng your skin with a sharp object and po 'sibly injecting chemica l s into your body
Acommon source of this type of injury is a chipped beaker, flask
or pipet Toke special care when inserting gloss tubing or a ther mometer into a rubber stopper; always use a slit-stopper and lubricate the gloss to ease insertion If you have to force it, you
FIRST AID
C heck wit h inst ruct or for lo cal gui deli n es
Burn f om hot hlbwarc:
M in or: App l y co l d water
SC I-io us : Contact medica l help
Cut
may snap the gloss tube and end up inserting it into your hand Absorbing chemica ls through your skin
NEVER handle any chemical with your bare hands Examine all cases of exposure to solid or liquid reagents, and toke the appropriate action to treat the harm to your skin Some solvents-for example, DMSO (dimethylsulfoxidel-easily pass through the skin and into deeper tissues
from broken glassware:
Mi no r: Wash with soap, apply antiseptic ointment and ster i I e bandage
S eriu us: Control bleedi n g by applying prcssure \\ ith sterile pad; contact emergency medical help
Be especially aware of the danger of chipped beakersand flask s Also, toke core when washing gloss labware; it gets slippery and
is easily dropped
Skin- exposure to a chemical:
Ri nse wi t h water ; iI' condition develops contact medical personnel
Feeling Jighthe ded or passing out:
Move affccted person to fresh air outside the lab ; contact mcdical person el if the cond ilion persist s
This can be a common problem when working with cylinders of compressed gases, such as (0, (02- even non-toxic gases such
as He and N2can displace the oxygen in the lob Burning clothin
Do nu t panic; drop to the floor and smo t her the flame
u se safety - hower t o treat burn ; con tact emcrgcnc mcd i al pe r onn
Trang 2I
.'
Some chcm icals arc toxic; all can cause harm if used Material Safety Data Sheet (MSDS)
incorrectly Lcarn about reagents bcforc using them in an A deta ed description of ev rything you ever want to
experiment Read y ur lab manual and textbook, and talk know ab ut a chemical So, whether you are using
to your instructor I in doubt, ask questions! water, mercury or sodi um chloride, ou can find out
Copies ofa MSDS should bc in the lab for all the chem
: t - - - F'IRFlash E HAPointsZA RD : icals you arc using Consult this material if you have any HEA LTH
4 - Below 73 g F qucstions about the risk associated with a chemica l
4 - Dea
1 - Slightly Hazardous Exceeding 2002 F Chemicals in the samc color group can normally bc
1 - Abo ve 2 00 Il F
o - No r mal material
0- Will no t bur" stored together; exceplions noted on the label
0 - Stable
NFPA Hazard Codes (National Fire Prevention Association)
(Highlights major chemical hazards)
XChemi(als that are toxic if inhaled, ingested or abl{)rbed through the skin
XChemicals that easily ignite; also, explosion hazard
X May read violently with air, water or other substances
cOITosivc Store in corrosion-resistant area EX: c(l// cellfrale {lacitl., 111111 bases
Oxidi zing acids separa ted fro m organic acids
X Chemicals that read with skin or other exposed tisSue,
GREEN or no serious May be stored in gcneral storag
haz
A storage group;
ruzn
d efi nitely do no t wa nt to sto re them on the same ca binet she lf
CHEMICAL SPILLS
o Larger spills: Notify the instructor; wear gimes and materials Most chemicals llllUld not bc pourcd down
shoe protectors, use a ~ pill kil designed for the chcmi
the drain Your institution may be penalized by fcderal
ca l Your lab should be eq uipped \\ ith tlwsc item s authorities if wast is not handled properly by you and
Clean up all spills prompty to prevent further accidents other students Mistakes as simple as unlabelcd waSIl'
You do not wont to track through any spill; it may dissolve bottles can rcult in substantial finc
your shoes!! All toxi metals and halogenated soh ents must be col
lected for proper disposal
On your clothing or skin
loxills may be active at very low levels
sse,s the ri 'k prescnted by the chcmica l Dilut.: solu
I part per hundred (% ) '/100 1: 100
tions of 1110st reagents do not present a major health
I part per million (ppm) '/1.1"".'"'0 1: 10"
risk rhink about a 0.1 M NaCI vs a 10.0 M IINO, rhe
I part per billion (ppb) '/.0'>1•.1100.""0 1:10' f'()fIller is harmless: the latter can cause major skin and
1 part per trillion (ppt) '/,.00" ".,0 1:10"
clothing damage
jar; it is "waste," Reagcnls arc often cxpensivc, so con
exposed skin with water
and apply first aid Treat
If a large r area is
exposed use the safCty
first aid Aftcr rirst
professional medi ca Remember- if you "sink it" today, you "drink if" tomorrow!
Dilution is NOT the solution to pollufion,
2
Water "The Universal Solvent"
boiling point: 100.0 "C freeling point: 0.0 "C density: 1.00 g/mL at 4 °C molar mass: IR.O 15 g vapor prcssure: 23 8 mm Il g, 25 "C
Non-polar compounds (EX: hexane an d ben.rcne) are soluble in non-polar organic solvents, but insoluble
Polar compounds (EX: amines alcohols, ol'ganic acids) tend to disso lve in water
Boiling pf Density (g/ml) Molar moss (g/mole) ethanol 79 "C 0.79 46.07 polar methanol 65 \IC 0.79 32.04 polar acctone 56 " 0.79 58.08 polar
(lC isopropanol R2 0.79 60.11 polar benzenc 80 0.88 78.12 nonpolar toluene III "C 0.87 92.15 nonpolar
Aqueous Solubility
ocelole [hloride fluoride lullole (orbonole oxide
[hromole
inlol inlol inlol inlol
I inlol inlol
Flame test: C haracteri s tic colors of iOIl ill violet: polossium, rubidium,
blue: copper (ozure), leod, arsenic, seleni green: copper (emerald),
yellow:
red: lithium (cormine),stron~um
Acids
C'o mmerciul l{ca gcn1
hydrochloric, IICI 11.6 M pungent nitrie, IINO 16.0 M o.xidiLcr sul furie,II,SO, 18.0 M dehydrating agcnt
glacial acetic 17.4 M phosphoric 14.7 M
Safety note- oxidizing acids should not be stored or mixed with organic acids,
Bases NaOl1 and KOII, hygroscopic pellets
NaOl1 19.1 M aqueous ammonia 14.X M pungent Common Chemical Reagents & Molar Mass oxygen gas (), 32.00 g mol nitrogcn gas Nl 28.02 glmol
hydrogen gas II , 2.016 g,mol chlorine gas CI, 70.90 g mol graphite or charcoal C 12.0 I g mol Properties of ir
Roughly 80°" N" 20"·'.0,
Water contcnt, variablc I 4( ~0
pl l -Iogw [II J pOll - -Iog lo [011 -1 pOIl+pH 14 Water sclf-ioni;ation: pK" 14
pH ra nge & examples
Strong
o 1 2 3 4 5 6 7 8 9 10 1 1 1 2 1 3 14
H,O
NaCt
NH:Salts Ac' or CO t Salts
Trang 3Acid-Base Indicator
I
mcresol green 4.0-5.6 YOI J I~IJJ - blue
phenolphthalein 8.0-10.0 C!", ~~"'U ,-red
co
¥ :l
~
i l
;g
~
~
,
"5
g
~
'"
"
E
~
-'L
- , ' - - - - ,
OH C03
HC0 3
N 3
N02
O2
PO
SO
503
CIO
NH
Charge
1
2'
1
1
1
2'
3'
2' 2' 1
1
hydroxide
ca rbonate bicarbonate
nitrate
nitrite
peroxide
phosphate
sulfa te sulfi te perchlorate ammonium
Molar :\Iass
17 01 g / m o l
60 01 g / mo l
6 1.02 g / m o l
62 0 1 g / m o l
4 01 g / m o l
32 00 g / mo l 94.97 g / m o l
96 97 g / mol
80 07 g / mol
99 45 g / m o l
1 8.04 g / mo l
3
Trang 4How to dispense lq uids
Cho ice of cq ipml.!nt de p~ n s
on desi red precision
LJ c a ,maII beak.er to obtaI n
the needed amou t fro m the
reagent bottl e
Try to ovoid toking extra
reagents Imagine if every student
in the lab used 3 times as much -'IIi"_
reagent as needed
Otherwise, you get more material on the outside of the flask
ond table than on the inside, where it should be
Note the precision of the volume measured by each piece of
Lab equipment is delicate and expensive; learn to usc it correctly Ask for assistance if you need he lp
Disciplined troining is required for any octivity requiring skill in
• science, sports, music or art You do not naturally serve aces at Wimbledon or shoot under por ot the U SOpen Championship
D not usc worn or frayed electrical cords
This con lead to dongerous electric shocks and the igniting of other flammoble materials in the lob If you hove equipment with these problems, contoct the instructor
Be aware of the risk of static electricity it may harm computers and can ign ite nammablc so lve lll This is more of 0 problem in dry climates ond in labs with cor·
peted floors (in the labs or in attoched hallways) equipment A flosk, buret and graduated cylinder all measure
volume with different precision
Use a weighing dish to h ld th sample; ispense from
(this may contaminate e entire supply)
Use a funnel 10 transfer into b ttle or fl sk
Be aware of the effects of air currents in the lab, especially
if you are working in a fume hood Your powdery solid could
end up spread all over the table, instead of in your beoker,
where it belongs
Step I: Insert the tip of the pipet into the liquid
suction bulb to draw liquid into the pipet past th.: desir
"mark" on th stem of the pip
fully release the va C UI1l and a ow thl' lquid to drai
fro m the pi
Step 3: lOp the n w at the deSIred ··m
Step 4: Ins'I1 pipet into the nask and release the lq id
Under no circumstances should you ever pipet using mouth
Ttion, even if you ore pipelling water or hormless solutions
T is creates a bad habit, and suddenly, while not thinking, you
have jUlt pipetted 0 mouthful of sulfuric acid
in the lab
Clean the pan with a son brush; if the pan is stainecl
\\ ith the assistance of the instructor, remove and clean
the pan
Zero the balance before usc; otherwise, all of your mass
data wi ll be inc or r~et
Usc a weighing dish to hold the sam ple; pre-weigh the
dish add the smpl , re-welgh sample and dish; dcter
mine sampl mass by dfference
Your dota will be meoningless unless the balance is properly
zeroed
EX: If tile l/ish h as a IIIlIS \ /I f 50 g 01111 t h e s lIlIIp le
p Ill s c1i ' " " 1 1' lIlIIlI ' \ /I{6.5 g t" e lIIa ss o f t" e samp le i ,
NEVER weigh chemicals directly on the balonce pan Clean up any
spilled chemical on or oround the bolance before you leave it
NEVER weigh a hot object-the heot generates oir currents
that alter the measurement
and
wih rubber tubIng
I!!nite the n
Adjust the air/gas mix to gi \
quiet, hot name The size o
name should "fit" your appli
tion mall te,t tubes only need
burns when working with a burner ond hot labware
How to use a hot plate
Plug the ho plate cord into the electrical outlet
Adjust the setting to gi\'e the tcmpcratun: required for
your app lication
Use tongs to manipulate the lab\\are on the hot plate
Do not simply set it on "high" and then forget obout it The sur
fate tan get hot enough to melt lead
Take core when using flammable solvents on or oround a hot
plote If spilled on the hot ceramic surface, ~
can ignite
Watch out for chipped or cracked glassware; discard in the glass-recycle box
Ask your instructor for guidance with disposal of any damoged lab equipment
Thermometer: Usc "non-mcrc ury" for routine work Unless you are in need of measurements over 120' C, you should never work with a mercury thermometer in your lab
Ref igerator: Store chemicals in sealed containers; do not store food with chem ica ls
Always follow your instructor's guidance on storing items in the
- lob refrigerator
Compressed-gas cytinders: Secure to a wall or bench;
fa lling cylinders cause se rious inju ries
troin you in the use of the valves and regulators Check for possible chemical hazards associated with the gas; EX: CO, CO2,
H2, O2, etc
11 data has ~ " umber" and ~ "unit.'·
If you need to use this type of equipment, your instructor will
Metric Co versio s
Mass I kg = 1,000 g
To convert "g" to "kg": divide by 1,000
I mg = 0.001 g
To convert "mg" to "g": divide by 1,000
Size I mm = 0.001 m
To convert "mm" to "m": ivide by 1,0 0
I cm = 0.01 m
To convert "cm" to "m": dividc by 100 Votume I mL = 0.001 L
To convert "mJ :' to " J :': divide by 1,000
I,OOOmL = IL
To convert 'T' to "mL": multiply by 1,000
Press ure 760 mm Ilg = I atm
To convert "mm Ilg" to '"atm": divide by 760
TemperatureT (K) = T (OC) + 273 15
To convert ''''C'' to "K": add 273.15
Time I hour 60 min = 3,600 sec
To convert "hI'S" to "min"
OR "min" to "sec": multiply by 60 With any unit conversion, it is eosy to use the wrong factor
Always double-check before using the data
Significant Figures (sigfig)
Record the number of digits appropriate for the mes
uring device, plus record one "approximate" digit
!:xponcnts are always signi fican t
Add/subtract: For final answer: the number of decimal
plaes is gi\ en by datul1l with thc le sl d cim~1 place Multiply/divide: !-or the final answer: th.: number of
• Sct range to usc all of th graph page; label axes and clearly mark data points
I' - 111 \ + h (11/ slope, iJ = " nterc pt)
data [Joints
With all lab data and calculotions-think!!!
Bolances and flasks, like calculators, n:lIl1mablc malcrials su b sta n ce I II "l-Uld IIIlilrilMtiutl III thl gUldc I'" 1\(1 1.1" a ,ub
lut e l ilr proli.· "iomll medlc:1 1 \:.11'1': III all) I ' uc Clllcr/.:cm.:) c~,11
\11 riJ!hl~ rt'~l'ncd '\jl) pan of lhi~ plrhli":,IIII)11 III.I~ Ix- IcproJul.".:d t\r lr.lll~mll1cd In are not equipped with a brain
to ask, "Does this number h.~m llf hy any IllC'llh, del'lrlinll." P I ' IlICl."hal!ll."dl Im: l udinjo[ phllllX:llp~ rl."corulllg 1'1 iln~
mtnrmalWll Iora!!.: and relnc\,.1 "', ICill \\llh"111 \Hlllcll p 'rnll' hlll tmm lilt.' pu~lhhcr , 20UI 20118 Bar("hHrl !> c UHOH
moke sense7"
PREPARING A SOLUTION
may need to prepare a solution from scratch or
dilutions of"stock" solutions Thc most tion concentration unit is molarity, M
A 1.0 M solution of NaCI contains 1.0 moles
in 1.0 Liter of
The moles of material in a given V molarity, M , is given by M .x
EX: Il ), oll l lisp ellse 0 50 L (!ll l 1.0 1\1 NaCI so lu
ti O Il y o u (l r t! wo r kill g w it"
Ceneral Cuidelines
Use volumetric glassware; add reagent dissol\e in
some solvent and then dilute to the "mark" on the nasI with additional so lvent
Organi7c the essental information before starting to prepare a so lu tion
When you are standing at the balance is not the time to ask yourself, "How much of this stuff do I need?"
Liq id re gen -you usually d~termine the mas from the
dispe nsed volumc and dens ity of the liquid:
Ifyou nced the exaet mass of the liquid reagent weigh out the desired quantity using a balance
Step I: Select volume, v-dif and deSIred
concentration c-di!
Step 2: Deteminc v-stock of re~gent of concentration
c-stoc k
Step 3: Use this equation to ca lculate v-stock: , -dif )
c- l = v-stock xc-stock
Step 4: Add enough solvcnt to dilute v-stock in a
volumetric nasI of volume ,-dil
volume, V
mo = C x V
Step 3 Calculate the mass (grams) of reagent from
molar mass, M; mass (grams) mol :\ 1\1
Step 4: Prepare solution using mass (grams),
using a volumctric nasI of volume, V
Dilutions of Acids & Bases
Always add acid (or base) to water, slow ly, with sti rring lleat is
produced in the process This
is true for liquid concentratcd
INO, or solid bases, such
as NaOl1 or KOII pellcts
Concentrated I,SO, is also
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o.;ubJccl: mlll!.:r il i i ntr.:l l lh.!J fur U"l' ill the ! h ,IIl II1l.:onjutl~linn ~
\ \ (1r" lind ,L lgncJ lC\h.l\citlll'r Ba rt haf h Ill c II' \\I'IIo.:r- editor- nor dt.!"gn <.1 arc in ;: 1Il ) , a)- r cspt uhi hl(' Of hahlc f or 1111,: u or 1ll1"U",C nf"lhc IIlf.'nnalIO!l l:tl n
in Ihi~ g ui de Alway Ilb cr\e pn.:cautiiln \~hcn INIl ~ d.l1l~croll'" dh:nm;al"
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