Tải bản đầy đủ

Quick study academic chem lab basics 600dpi

Think Again!
like skill in sports, music or art-docs not
come naturally to anybody. uccess in each of thcse
areas depe nds on discip line, practi ce and tra inin '. In
the chemi stry lab, you encounter ncw equ ipment and

varied types of chemical materia ls, requi ring training if

you plan to usc them sa fe ly.

Remcmber, details arc importan t in chem istry and

not just where numbers and ca lculat io ns arc concerned.

Chemical names and formu las present a whole new

li ngo. You have to know these symbols and defini­

t ions to wOI'k in t he lab.



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 try
lab, and a respo ns ibility sha reo by studen ts a nd
instructors.
Learning about safety is part of yo ur ed ucat io n; skil ls
you gain in the lab will serve you in 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 how to get out q ui ckly in an
emergency.

Never work in on isolated "corner" of a lob; upper-floor
windows do not count as emergency exits.

Where is thc nearest p ho nc '! You

may neeo fo call for emergency

help. If so, di al ill or your

local cmergency number.


Do not rely on the cell

phone in your book bag­

it may be on fire!

• 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 was hing s~in and/or eyes ex posed to
chemicals.
• Where is the fil'c extin!!uis her? You may need to u~ e it
to do use small fires. Check with your instructor on
guidelines for using an ext ing ui sher. So m e fires
require special treatment.

Sodium reacts with water, a common ingredient in
most fire extinguishers.
Personal Respo nsibil ity
R ule I: Protect yourseln Your mi stakes will likely harm
you more than anyon e else.
Rule 2: Reael the lab manual be lore class. Come to lab pre­
pared to work on the assigned ex periment.
­
R ule 3: Always pay atte nt ion as yo u work. Watch other
students; you ar impacted by their mistakes.
Rule 4: Clean up your own mess. You arc a partner in
ma intaining a sa fe lab.
Kevs to a Clean Lab
Keep your work space clean and organi zed .
Wash labware wit h detergent: ri nse with de- ioni7ed or
disti lled water; usc a wash bottl e to conserve water;
drain excess liquid; a llow object to d ry be fo re stori ng.
• Shared eq ui pment
wash before a nd afte r
each use.
• After each lab se ss ion , return reagents and
eq ui pme nt to the des ig nated storage areas.

X D anger!

• Always work with instructor supervi sion . Never wor k
in a lab alone.
Iways wear goggles in the lab..
even ov I' eyeg la sse s: replace
contact lenses \\ ith eyeg lasses.

(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.
So, switch to glosses for lob sessions.
• Wear an apron, lab coat and g loves to
limit your chemi ca l exposure and to save c lothing from
ch.;mical stain 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.

Wh ile working in the lab, yO U will usc a number of
reagents, giving ample chance for exposure to the harmful
effects of chem ical s. In some cases, exposure will be due
to an acc identa l spi ll ur breakage of equipmcnt. Other lim­
ited ex posure may come as a result of using the chemicals
as directed. If yo u can smell a vo tatile chemical, it could
hal-m you . Your scnse ofsmel l is very sens itive. rcfkcting
your body's scnsitiv ity to all types of odors. Thi s also
reflects the efficiency of our biochemistry and explains
why we have adverse reactions to minute quant ities of cer­
tain chcmicals.

Possible Risks of Exposu re
Inha ling chcmica l rowdcr or vapor. Takc care when
working wit h any vo lati le solvents.

Remember, if you can smell it, it could be harming you.
Ingesting so li d o r liquid chcm icals 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.

• Wear closed-toe shoes and long pants to protect your
Icct and legs .

Punctur ing your skin with a sharp object and po 'sibly
inj ecting chemica ls into your body.

These precautions provide protection from spilled chemicals and
broken gloss.

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
may snap the gloss tube and end up inserting it into your hand.

• Tic back hair and avoid bulky s leeve s that II1tcrfe re with
work.

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.

Absorbing chemica ls th rough 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.

Food and drink shoul d not be brou ght into the lab.

This greatly enhances the chance that you will accidentally
consume lob chemicals along with Ihe drink or snack,
Wa sh your hand s alier each lab sess ion. bcfi) rc leaving.

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!

FIRST AID
C heck with instructor
for local guideli nes.

Burn from hot hlb wa rc:
M inor: App ly co ld water.
SC I-io us : Contac t medica l help.

Cut from bro ken glassware:
Heating Labware
U~c to ngs to handle la bwarc whil e it is hcatcd by a
burner o r hotplate .
All ow the item to coo l to room
tem peraturc before weighing.

Hot lob items do not look hal,
Hot ilems create air currents that

alter the reading of a balance.


Liq uid Reagent
Cover the beaker with a watch t!l ass.
Use " bo iling stones' to promow smoot h bo iling.
Flam mable solwnt : Ta ke care when heatin g \\ ith a hot
pl ate; avoid usc of ga s burner.
Handle test tube \\ ith wire-holder.

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.

Solid Reagent
Use a weigh ll1g di,h on the
balance.

Cover the dish to prevent

loss. sp ill s o r contam inatioll .


Always record lob data in on
organized notebook, including
the number and unit.

Mi no r: Wash with soap, apply antiseptic ointment and
ster iIe bandage.
Seriu us: Cont rol bleedi ng by applying prcssure \\ ith
sterile pad; contact emergency medical help .

Be especially aware of the danger of chipped beakers and flask s.
Also, toke core when washing gloss labware; it gets slippery and
is easily dropped.
Skin-exposure to a chemical :
Ri nse wi th water; i I' condition develops. contact medical
personnel.

Feel ing Jightheaded or passing ou t:
Move affccted person to fresh air outside the lab ; contact
mcd ical personnel if the cond ilion persist s.

This can be a common problem when working with cylinders of
compressed gases, such as (0, (0 2- even non-toxic gases such
as He and N2can displace the oxygen in the lob.
Burning cloth ing:

Do nut panic; drop to the flo or and smother the flame ;

use safety -hower to treat burn ; con tact emcrgcncy

mcd i al personnel.


DO NOT use a fire blanket; these only complicate subsequent
medical treatments for burns.
Summary
Good lab planning and prevcntion of accidents is the bcst
fi rst aid . Do not be hcmic! Dcal \\ ith cuts and minor
chcmical c-.posure . Call emergency personne l for
anything that is major.


.
Some chcm icals arc toxic; all ca n cause harm if used
incorrectly. Lcarn about reage nts bc forc usin g them in an
experiment. Rea d your lab manua l and textbook, and talk
to you r instruc tor. Ir in do ubt, ask q uestio ns!
: t - -HEA LTH
4 - Deadly

3 - Extreme danger

2 - Hazardous
1 - Slightly Hazardous
o - Normal material

F'IR E HAZARD
Flash Points:
4 - Below 73g F
3 - Below l00g F

- Above l00 2 F, Not
2002 F

Exceedi ng
1 - Abo ve 200IlF

0- Will not bur"

W-

Radioactive

Of

4 - May detonate
3 - Shock and heat
may detonate
2 - Violent chemica l

change
1 - Unstable if heated
0 - Stable

NFPA Hazard Codes (National Fire Prevention Association)
(Highlights major chemical hazards)

J T Baker System
BLUE
healt h hazard Store in secure (lockcJ) poison arca . EX: cYllllides, lIIeI"CIII:I'

Chemi(als that are toxic if inhaled, ingested or abl{)rbed through the skin.


X

RED

fla mma ble
hazard

Storc in a '" nammablc IiCJu ids"
EX: (IC('(Olle, orgllllic soillellfs

storage a rca .

Chemicals that easily ignite; also, explosion hazard.


Organic Compou nds - G eneral Ru les
Non-polar compounds (EX: hexane an d ben.rcne) are
soluble in non-polar organic solvents, but insoluble
in water.

reactiv ity
hazard

tore in an area iso latcd /i·OIll
EX: rellcth,c lII elal." clllciulII or sodiulII
llall1lllabl cs and cOlllbustibles.
May read violently with air, water or other substances.

cOITosivc
hazard

Store in corrosion-resistant area.
EX: c(l// cellfrale{lacitl., 111111 bases
Ac id s and bases eparalcd.
Oxidi zing acids separa ted fro m organic acids.
Chemicals that read with skin or other exposed tisSue,

Organic Solvents
Boiling pf
79 "C
ethano l
methanol
65 \IC
acctone
56 "
isopropanol R2 (lC
benzenc
80
III "C
toluene

X

X

May be stored in gcneral storage.


IJIAG ONAL incoillpatibies
STRIP E

Storc with ca ut io n.

V Reads with other materials in that

A storage group; store each one separately.


ocelole
[hloride
nilrole
bromide
per[hlorole iodide
[hlorole

On your cl oth ing or skin
sse,s the ri 'k prescnted by the chcmica l. Dilut.: solu­
tions of 1110st reagents do not present a major health
risk. rhink about a 0. 1 M NaCI vs. a 10.0 M IIN O,. rhe
f'()fIller is harm less: the latter can cause major skin and
clothing damage.
o If needed,
renwvc a rreeted
artic le of clothing; was h
exposed sk in with water
and apply first aid. Treat
pn'!11ptly to minimi/c

hann.

I f a large r area is
exposed use the safCty
shower, then apply
first aid. Aftcr rirst
aid, follow up with

professional medi ca l

treatment.

fluoride

lullole

(orbonole
,ulfide
pholphole
hydroxide
[hromole

oxide

lorm
hydroxide

melo~,

inlol
inlol
inlol
inlol
I
inlol
inlol
Inlol
Inlol
inlol
insol
insol
Inlol
insol
insol
Inlol
insol
insol
Flame test: C haracteristic colors of iOIl ill a flame


polossium, rubidium, cesium

copper (ozure), leod, arsenic, selenium

copper (emerald), borium (yellowish), zinc (whitish)

sodium

lithium (cormine), stron~um (\Corlet), calcium (yellowish)

C'ommerciul l{cagcn1

CHEMICAL SPILLS

You do not wont to track through any spill; it may dissolve
your shoes!!

Molar moss (g/mole)
46.07 polar
32.04 polar
58.08 polar
60.11 polar
78.12 nonpolar
92.15 nonpolar

alkali

violet:
blue:
green:
yellow:
red:
Acids

Summary

Always consider the property before you use a chemical.

If two chemicats react, for exam pte Het and ammonia, you

defi nitely do not wa nt to store them on the same cabinet shelf!


On the floor or bench to p
o For small spill s: Wear glmcs, neut ra lil.c acid 'base;
absorb usi ng paper towels and di scard in a labe led b"g.
Make sure the .Ioves arc resistant to thc chemical that
is >pilled .
o La rger spills: Notify the instructor; wear gim es and
shoe protectors, use a ~pill kil des igned for the chcmi­
ca l. Your lab should be eq uipped \\ ith tlwsc item s.
Clean up all spills promptly to prevent further accidents.

Density (g/ml)
0.79
0.79
0.79
0.79
0.88
0.87

Properties of Inorgan ic Salts
Aqueous Solubili ty

X

GREEN or no serious
hazard


ruzn

'

Liquid Solubility Rule: "Like Dissolves Like"
Wate r "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

Polar compo unds (EX: amines. alcohols, ol'ganic acids)
tend to disso lve in water.

I I

SP ECIFIC HA2:ARI) - --+"
Oxidizer
Acid
ACID
Alkali
ALK
Corrosive
COR
Use NO WATER

Material Safety Data Sheet (MSDS)
A detail ed description of ev ryt hing you eve r want to
know about a chemica l. So, whether yo u are using
water, mercury or sodi um chloride, you ca n find out
how thi s material should be handl ed.
Copies ofa MS DS should bc in the lab for all th e chem­
ica ls you arc usi ng . Consult th is material if you have any
qucstions about the risk associated wi th a chemica l.
Chemical S to rage C od es
Chemicals in the samc color group ca n norm ally bc
stored toget her; exceplions noted on the label.

"Wast~" is a term \\ ith specific mcaning in the chemi­
cal community. r cderal , state and local laws mandate
how chemi , u' labs hand le the excess sol vents and
othc r eh mi cal s th ai arc ge nc ra ted by ch emi sts.
Chemi ca l waste may or may not be hazardous.
I ollow thc instructor 's diredion s for di sposal of all lab
material s. Most chemi cals SllllUld not bc pourcd down
the drain . You r insti tution may be penali zed by fcdera l
authorities if waste is no t hand led properly by you and
other students. Mistakes as simple as unlabelcd waSIl'
bottles can rcsult in substantial fin cs.
All toxi metals and halogenated so h ents must be col­
lected for proper di sposal.
loxills may be ac tive at very low levels.
1: 100
I part per hund red ( % ) '/100
1: 10"
I pa rt per million (ppm) '/1.1"".'"'0
1: 10'
I part per billion (pp b) '/,.0'>1•.1100.""0
1:10"
1 part per trillion (ppt) '/,.00"..."..".,.•0.
Waste Prevention: Usc only the requ ired amount of
reagent. Excess mat rial cannot hc returned to rcagcnt
jar; it is "waste," Reagcnls arc often cxpensi vc, so con ­
servation helps keep lab costs 10\\ . A spot plat ' is an
excellent means to co nserve reagents.
GE NE RAL RULE : When in doubt, coll ect all ,olu­
tions used in the lab in labe led waste bottles. Make slire
that any chemical that is poured into thc , ink is not
going to react in the ,cm:r lin e or contribute to pollu­
ti on. Most loca l water-treatmcn t faciliti es mon itor
water from school labs.
Remember- if you "sink it" today, you "drink if" tomorrow!
We only borrow wafer for home use, drinks and food preparation.
Dilution is NOT the solution to pollufion,

2

hydrochloric, IICI
11.6 M
pungent
16.0 M
o.xidiLcr
nitrie, IINO
sul furie,II,SO,
18.0 M
dehydrating agcnt
acctic
6.27 M
17.4 M
glacial acetic
phosphoric
14.7 M
Safety note- oxidizing acids should not be stored or mixed
with organic acids,
Bases
NaOl1 and KOII, hygroscopic pellets
Commercial

Ilca ~cnl

NaO l1
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
pH Kev equations
pl l -Iog w [II J
pOll - -Iog lo [011 -1
pOIl+pH 14
Water sclf-ioni;ation: pK" 14
pH ra nge & examples
Strong

Acid

o

Strong


Acid

1 2 3 4 5

Base

Neutral

6 7 8 9 10 11 12 13 14
Base

H,O
H,CO,
HAc
NaCt
NH:Salts

NH,
Ca(OH),
Ac' or COt Salts

NaOH
KOH


Acid-Base Ind icators

Com pounds that change co lor as the pll changes .

Se lecti on: Pick to matc h thc pll ru nge of the sa lt pro­
duced by a titration or other process.

Name

Range



Acid-Base

Color


4.0-5.6

YOIJ I~IJJ-blue

m ethyl red

4.4-6.2

red- YOIlbJJ

phenol red

6.4-8.0

y.sdJ:.IJJ-red

thy m ol blue

8.0-9.6

YOIHc.IJJ-blue

phenol p hthalein

8.0-10.0 C!", ~~"'U

mcresol green

,-red

-

- -- _.--...

tv

¥
:l
~

il
;g
~

..,
~

"5

g

.
~

'"

~

,' - - - - ,

6.022 x 1023 mol-I
Avogadro's Number, N,,:
9. 1lO x 10-' 1 kg
Mass of electron, me:
1.673 x 10-27 kg
Mass of proton. m,,:
1.675 x 10- 27 kg
Mass of neutron, mn:
6.626 x 10-34 J S
Pl anck's Constant, k:
1.602 x 10- 19 C
Electron charge, e:
Faraday Constant, F:
96,485 Clmol
Idea l Gas Constant, R:
for gas calcu la tions: 0.082 L atm mol-I K- 1
fo r energy calcu lati ons: 8.314 J K-I mo l-I
2.9979 x lOx m/s
Speed of light:
Standard temperature and pressure (STP ): I atm and 0 "C
Vo lume o f Ideal Gas at STP: 22.414 Llmo l
Typi ca l room tempe rat ure:
20 25 "e

co

~.

..

-'L

1 "1'!I~

.."

E

z

3

Cha rge
OH
C0 3
HC0 3
N0 3
N0 2
O2
P O.
SO.
503
C IO.
NH.


2'



2'
3'

2'
2'



hydrox ide
c a rbonate
bicarbonate
nit rate
nitrite
peroxide
phospha te
su lfa te
sulfi te
perchlorate
ammonium

Molar :\Iass
17.01 g/mol
60 .01 g/mol
61.02 g/mol
62 .01 g/mol
46.01 g/mol
32 .00 g/mol
94.97 g/mol
96.97 g/mol
80.07 g/mol
99.45 g/mol
18.04 g/mol


PREPARING A SOLUTION
How to dispense liq uids
Cho ice of cquipml.!nt de p~ n d s
on desi red prec ision.
LJ. c a ,ma II beak.er to obtaIn
the needed amount fro m the
reagent bottl e.
Try to ovoid toking extra
reagents. Imagine if every student
in the lab used 3 times as much
reagent as needed .
Usc a funnel to tran~fc r to a il a, k.
Otherwise, you get more material on the outside of the flask
ond table than on the inside, where it should be.

-'IIi"_.

Note the precision of the volume measured by each piece of
equipment. A flosk, buret and graduated cylinder all measure
volume with different precision.

How to d ispense solids
Use a we ighi ng dish to hold the sa mple; dispense fro m
a beaker us ing a spatul a. not fm m the reagent bottle
(thi s may contaminate the ent ire supply).
Use a funnel 10 transfer in to bottle or fl ask .
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.

How to use a pipet

Step I: Insert the tip of the pipet into the li quid. Use a

suct ion bulb to draw liqui d into the pipet. past th.: des ired

"mark" on th stem of the pipet.

Step 2: Qui ckly replace the bul b with) our finger; ca re­

fu lly rel ease the vaCU UI1l and all ow thl' liqui d to drain

fro m the pipet.

Step 3: lOp the now at the deSIred ··mark."

Step 4: Ins'I1 pipet into the nask.. and re lease th e liquid.

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.

Ho\\ to use a balance
Manual triple-beam and electronic bal ances arc used
in the lab.
Clean the pan with a so n brush; if the pan is stainecl
\\ it h the assistance of the instructor, remove and clean
the pan.
Zero the balance before usc; oth erwise, all of your mass
data wi ll be incor r~et.
Usc a we igh ing dish to hold the sam pl e; pre-weigh the
dish. add the sampl , re-welgh sam ple and dish; dcter­
mi ne sampl e mass by dlffe rence.
Your dota will be meoningless unless the balance is properly
zeroed.
EX: If tile l/ish h as a IIIlIS.\ /If 5. 0 g 01111 th e slIlIIple
pIlls c1i.' " " 11' lIlIIlI.' .\ /I{6.5 g. t"e lIIass of t"e sample i,
6.5 g - 5.0 g = 1.5 g,

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.
How to use a gas burner
ccurciy con nect bu rner to the gas supply
with rubber tubI ng.
fa dua lly inc rease gas flow
and
I!!nite the name.

Adjust the air/gas mix to gi \ c a

quiet, hot name. The size o r the

name sh ou ld "fit" your applica­

tion. mall te,t tu bes only need a

sma ll namc.

Be especially owore of the risk of

burns when working with a burner ond hot labware.


How to use a hot plate
Pl ug the hot plate cord into the electrical outlet.
Adjust the sett ing to gi\'e the tcmpcrat un: req uired for
your app li cati on.
Use tongs to manipul ate the lab \\are on the hot pl ate.
Clean the hot p lat~ surface after it ha. cooled.
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.

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. S. Open Championship .
Do 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 electr icity 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) .
Watch out for chipped or cracked glasswa re; disca rd 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.
Refr ige rato r: Store chem ica ls in sealed contai ners; do
not store food with chem ica ls.
Always follow your instructor's guidance on storing items in the
- lob refrigerator.
Co mpressed-gas cytind ers: Secure to a wa ll or bench;
fa lling cylinders cause se rious inju ries.
If you need to use this type of equipment, your instructor will
troin you in the use of the valves and regulators. Check for
possible chemical hazards associated with the gas; EX: CO, CO 2,
H2, O2, etc.

Chemical reagents arc often dispensed as solutions. You

may need to prepare a solution from scratch. or prepare

dilutions of"stock" solutions. Thc most common solu­

tion concentration unit is molarity, M.

A 1.0 M solution of NaCI contains 1.0 moles of aO

in 1.0 Liter of solution.

The moles of material in a given V of solution of

molarity, M, is given by M .x V.

EX: Il),oll llispellse 0.50 L (!lll 1.0 1\1 Na CI solu­

tiOIl , y ou (l rt! wor killg wit":

0.50 L x 1.0 mol Na Ci/ L = 0.5 m oles ofNlICI.

C enera l C uidelines
Use volumetric glassware; add reagent. dissol\e in
some solvent and then dilute to the "mark" on the nasI..
with additional so lvent.
Organ i7c the essential 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?"
Liquid reagent - you usually d~termine the mas. from the
dispe nsed volumc and dens ity of the liquid:
mass (g) = vol (mL) \ densif) (g/mL)
Ifyou nced the exaet mass of the liquid reagent. weigh out
the desired quantity using a ba lance.

Dilute Sol utions from Stock
Step I:
Step 2:
Step 3:
Step 4:

Se lect
volume,
v-d if,
and
deSIred
concen trat ion. c-di!.
Deteminc v-stock of re~gent of concentration
c-stoc k.
Use this equation to ca lculate v-stock: , -dif ).
c-di l = v-stoc k xc-stock
Add enough solvcnt to dilute v-stock in a
volumetric nasI.. of volume ,-di l.

Dil ute Sol utio ns from Pure Rea ge nts
Step I:

11 data has

~

"lI um ber" and

~

"unit.'·

Metric Conversions
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" : divide by 1,000
I cm = 0.0 1 m
To convert "cm" to "m": dividc by 100
Vot ume
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
760 mm Ilg = Iatm
Press ure
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 mi n = 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.

Select the desired concentration, C. and
volume, V.
Step 2: Determine the required number of moi<:s:
mol = 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.
Dil utio ns 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 liqu id concentratcd
ac ids, such as II .SO, or
0
IINO ,. or so li d bases, such
as NaO l1 or KO II pel lcts.
Concentrated II,SO, is also
a dehydrating agent.

Customer Hotline # 1.800.230.9522

U.S. $4.95

6

Signifi cant Figures (sigfig)
Record the num ber of dig its appropriate fo r the meas­
uring device, plus record one "approx imate" digit.
!:xponcnts are always signi fican t.
Add/subtract : For fi nal answer: the number of dec imal
pl aces is gi\ en by datul1l with thc leasl d ccim~1 places.
Multiply/divide: !-or the final answer: th.: number of
, igrigs is gi\.:n by th e datum with thL' least sigfigs.
G rap hing (x. y) data
• Sct range to usc all of the graph page; label axes and
clearly ma rk data points.
Equation fo r a lim'
I' - 111.\ + h (11/ slope, iJ = " -i ntercept)
Average or Mean Value
SUIll all data va lues and divide by the number of
data [Joints.
With all lab data and calculotions-think!!!
Bolances and flasks, like calculators,
are not equipped with a brain
to ask, "Does this number
moke sense7"

~---------------4~'-=---~----~

o
LLllLL

ISBN-13: 978-142320418 - 3
IS BN-10: 142320418 - 2

911~ llll~~IIIII!~111!llIJllllrlll lfl lill l

free d~wn~adS &

nun re

0.1. I

es at

qUlc s uuy.com
Author: Mark D. Jackson, Ph .D.
Artwork I Layout: Cathie Richards
'OTE TO STlln.' I: J hi ... gUltk i" inh..'lldl.'tl hlf IIlfnnnallllllal purJlO....:..

unly. Dw to its !.:onul!n"cd fllnlliLl. lhi ~ gUH..k emlllOI":t)\!.:1 \':\l'1) U'.. pCl'lllfth....

o.;ubJccl: mlll!.:r il i... intr.:l llh.!J fur U"l' ill the !..h ,IIlU II1l.:onjutl~linn ~ ilft l'tIUN:

\\ (1r" lind ,L.....lgncJ lC\h.l\citlll'r Bart hafh. Illc. II'. \\I'IIo.:r-.. editor- nor dt.!"gn <.1.111 .

arc in ;:1Il) , ... a)- rcspt uhi hl(' Of hahlc for 1111,: u...... or 1ll1"U",C nf"lhc IIlf.'nnalIO!l l:tl nt.lim:d

in Ihi~ guide. Alway ... Ilb...cr\e pn.:cautiiln... \~hcn INIl ~ d.l1l~croll'" dh:nm;al" and~)r

n:lIl1mablc malcrials su bstance ... I II--"l-Uld IIIlilrilMtiutl III thl ... gUldc I'" 1\(11 .1" a ,ub.. tl­

lute lilr proli.·... "iomll medlc:1 1\:.11'1':. III all) Il'uc Clllcr/.:cm.:). c~,11 '111.

\11 riJ!hl~ rt'~l'ncd . '\jl) pan of lhi~ plrhli":,IIII)11 III.I~ Ix- IcproJul.".:d t\r lr.lll~mll1cd In .111\

h.~m. llf hy any IllC'llh, del'lrlinll." PI' IlICl."hal!ll."dl. Im: ludinjo[ 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 !>. lnc. UHOH

I




Tài liệu bạn tìm kiếm đã sẵn sàng tải về

Tải bản đầy đủ ngay

×