ki1101-2012-kd lec02b themoleandstochiometry

8/11/2019 KI1101-2012-KD Lec02b TheMoleAndStochiometry

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Mole and StochiometryMole and Stochiometry

Achmad Rochliadi

Program Studi Kimia

Intstitut Teknologi Bandung


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Stoichiometric PathwaysStoichiometric Pathways


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Molecular Scale vs Lab.ScaleMolecular Scale vs Lab.Scale


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Defining The MoleDefining The Mole Counting $ormula units by moles is no di$$erentCounting $ormula units by moles is no di$$erent

than counting eggs by the do&en () eggs* orthan counting eggs by the do&en () eggs* orpens by the gross (++ pens*pens by the gross (++ pens*

Atomic mass provides a means to count atoms byAtomic mass provides a means to count atoms bymeasuring the mass o$ a sample.measuring the mass o$ a sample.

he periodic table atomic masses o$ the elements.he periodic table atomic masses o$ the elements. he mass o$ an atom is called itshe mass o$ an atom is called its atomic mass.atomic mass.

he mass o$ a molecule is thehe mass o$ a molecule is the molecular mass.molecular mass.

1 mole1 mole is the e!ual number o$ atom inis the e!ual number o$ atom in exactlyexactly12 gram of !1212 gram of !12atom.atom.

1 mole1 mole- ./)) 0 (/- ./)) 0 (/)1)1particles he Avogadroparticles he AvogadroNumbers*.Numbers*.


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2sing 3ater molar mass (4./(5* as an2sing 3ater molar mass (4./(5* as an

e0ample6e0ample6

( mole 7( mole 7))88 ./)) 0 (/./)) 0 (/)1)1molecules 7molecules 7))88

( mole 7( mole 7))88 (4./(5 g 7(4./(5 g 7))88

(4./(5 g 7(4./(5 g 7))88 ./)) 0 (/./)) 0 (/)1)1molecules 7molecules 7))88

9ithin chemical compounds, moles o$ atoms9ithin chemical compounds, moles o$ atoms

al3ays combine in the same ratio as theal3ays combine in the same ratio as the

individual atoms themselves so6individual atoms themselves so6 ( mole 7( mole 7))88 ) mole 7) mole 7

( mole 7( mole 7))88 ( mole 8( mole 8


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onverting grams to moleonverting grams to mole

7o3 many moles do 3e have in )1.5 gram7o3 many moles do 3e have in )1.5 gram

itanium :itanium :

ools 6 ( mol o$ i - +;.4; g iools 6 ( mol o$ i - +;.4; g i

Solution 6Solution 6


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onverting mole to gramsonverting mole to grams

An e0periment needed /.)5+ moles o$ FeClAn e0periment needed /.)5+ moles o$ FeCl11,,

ho3 many grams 3e need to 3eight :ho3 many grams 3e need to 3eight :

ools 6 ( mol o$ FeClools 6 ( mol o$ FeCl11- ().)/+ gr FeCl- ().)/+ gr FeCl11Solution 6Solution 6


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onverting "rom Labs Scale to #tomic Scaleonverting "rom Labs Scale to #tomic Scale

A nanotechnologyA nanotechnology

e0perimente0periment

re!uires + 0 (/re!uires + 0 (/))atoms o$atoms o$

potassium : 9hatpotassium : 9hatis mass o$ theis mass o$ the

sample :sample :


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Mole to Mole onversion "actorsMole to Mole onversion "actors

Consider a molecule o$ 9AE"Consider a molecule o$ 9AE"


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Feg5.10

OFeg0.15

Femol1

Feg85.55

OFemol1Femol2

OFeg9.159OFemol1

32 3232

32

E0ample6 7o3 many grams o$ iron areE0ample6 7o3 many grams o$ iron are

in a (5./ g sample o$ iron


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alculating amount of one element from thealculating amount of one element from the

amount of another element in a com$oun%amount of another element in a com$oun%

Exercise :Exercise :Pepto-Bismol, which helps provide soothing relief for anPepto-Bismol, which helps provide soothing relief for an

upset stomach, contains 300. mg of bismuthupset stomach, contains 300. mg of bismuth

subsaliclate,subsaliclate, !!"#"#$$#%#%BiBi33&"#", per tablet. 'f ou ta(e two, per tablet. 'f ou ta(e twotablets for ourtablets for our stomach distress, how man moles of thestomach distress, how man moles of the

))active ingredient** are ou ta(ing+ $ow man grams of))active ingredient** are ou ta(ing+ $ow man grams of

Bi are ou consuming in two tablets+Bi are ou consuming in two tablets+


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he usual $orm $or describing the relativehe usual $orm $or describing the relative

masses o$ the elements in a compound is a listmasses o$ the elements in a compound is a listo$o$ percentages by masspercentages by mass

his is called thehis is called the $ercentage com$osition$ercentage com$ositionoror

$ercentage com$osition by mass$ercentage com$osition by mass he percentage by mass is the number o$ gramshe percentage by mass is the number o$ grams

o$ the element in (// g o$ the compound ando$ the element in (// g o$ the compound and

can be calculated using6can be calculated using6

100%element%samplewholeofmass

elementofmass

Percentace om$ositionPercentace om$osition


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%74.06100%O%%25.94100%N%

sampleg0.5462

Og0.4045

sampleg0.5462

Ng0.1417

E0ample6 A sample 3as analy&ed and $oundE0ample6 A sample 3as analy&ed and $ound

to contain /.(+(; g nitrogen and /.+/+5 gto contain /.(+(; g nitrogen and /.+/+5 g

o0ygen. 9hat is the percentage compositiono0ygen. 9hat is the percentage compositiono$ this compound:o$ this compound:

ANAL#S


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Determining &m$irical an% Molecular "ormulasDetermining &m$irical an% Molecular "ormulas

Halothane C2H!ClF3

M(C2H!ClF3" # 2MC$MH$M!$MCl$ 3MF

# 2 & 12.01" $ 1.01 $ 79.90 $ 35.45 $ 3 & 19.00"

# 197.38 g'mol

hemical om$ositionhemical om$osition

(ole !at)o nC'nhalothane

(ass !at)o mC'mhalothane


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&xam$le&xam$le

Calculating the Mass Percent Composition of a Compound

Cal*+late the mole*+la! mass

M(C2H!ClF3"

# 197.38 g'molFo! one mole of *ompo+n,- fo!m+late the mass

!at)o an, *one!t to pe!*ent:

%17.12%10038.197

"01.122%

g

gC


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&xam$le&xam$le

%88.28%10038.197

"00.193%

%96.17%10038.19745.35%

%48.40%10038.197

90.79%

%51.0%10038.197

01.1%

%17.12%10038.197

"01.122%

g

gF

ggCl

g

gBr

g

gH

g

gC


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lassic H analysislassic H analysis

%ure o0igen added to the compound. Combustion products%ure o0igen added to the compound. Combustion products

are absorbed by chemical in 2@tubes. Calcium sul$ate absorbsare absorbed by chemical in 2@tubes. Calcium sul$ate absorbs

3ater, and sodium hydro0ide absorbs carbon dio0ide.3ater, and sodium hydro0ide absorbs carbon dio0ide.

E0ample reaction o$,E0ample reaction o$,

)C7)C71187 1887 18)) )C8)C8 11+7+7))88


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&m$irical formula&m$irical formula

(.(. Choose an arbitrary sample si&e (//g*.Choose an arbitrary sample si&e (//g*.

).). Convert masses to amounts in moles.Convert masses to amounts in moles.1.1. 9rite a $ormula.9rite a $ormula.

+.+. Convert $ormula to small 3hole numbers.Convert $ormula to small 3hole numbers.

5.5. Multiply all subscripts by a small 3holeMultiply all subscripts by a small 3hole

number to maBe the subscripts integral.number to maBe the subscripts integral.

5 /tep app!oa*h


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Determining the Empirical and Molecular Formulas of a

Compound from Its Mass Percent Composition.

)+tl s+**)nate )s an )nse*t !epellent +se, aga)nst ho+sehol,

ants an, !oa*hes. ts *ompos)t)on )s 62.58% C- 9.63% H an,

27.79% O. ts e&pe!)mentall ,ete!m)ne, mole*+la! mass )s230 +. hat a!e the emp)!)*al an, mole*+la! fo!m+las of

,)+tl s+**)nate

Step 1: ete!m)ne the mass of ea*h element )n a 100g sample.

C 62.58 g H 9.63 g O 27.79 g

&xam$le&xam$le


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Step 2: Cone!t masses to amo+nts )n moles.

OmolOg

OmolOgn

HmolHg

HmolHgn

CmolCg

CmolCgn

O

H

C

737.1999.15

179.27

55.9008.1

163.9

210.5011.12

158.62

Step 3: !)te a tentat)e fo!m+la.

Step 4: Cone!t to small whole n+me!s.

C5.21H9.55O1.74

C2.99H5.49O

&xam$le&xam$le


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Step 5: Cone!t to a small whole n+me! !at)o.

(+lt)pl 2to get C5.98H10.98O2

he emp)!)*al fo!m+la )s C6H11O2

Step 6: ete!m)ne the mole*+la! fo!m+la.

mp)!)*al fo!m+la mass )s 115 +.

(ole*+la! fo!m+la mass )s 230 +.

he mole*+la! fo!m+la )s C12H22O4

&xam$le&xam$le


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StoichiometryStoichiometryis the study o$ theis the study o$ the

mass relationships in chemicalmass relationships in chemical

compounds and reactionscompounds and reactions A common use $or stoichiometry is toA common use $or stoichiometry is to

relate the masses o$ reactants neededrelate the masses o$ reactants needed

to maBe a compoundto maBe a compound hese calculations can be solved usinghese calculations can be solved using

the $actor@label method and e!uivalencethe $actor@label method and e!uivalence

relations relating molecular massesrelations relating molecular masses

andor $ormula massesandor $ormula masses


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)alancing &(uation Strategy)alancing &(uation Strategy

alance elements that occur in only onealance elements that occur in only onecompound on each side $irst. Start 3ith thecompound on each side $irst. Start 3ith themost complicated $ormula $irst.most complicated $ormula $irst.

alance $ree elements last. 8alance $ree elements last. 8)) and 7and 7))usually should be le$t until the end*.usually should be le$t until the end*.

alance unchanged polyatomics or otheralance unchanged polyatomics or other

groups o$ atoms* as groups.groups o$ atoms* as groups. Fractional coe$$icients are acceptable andFractional coe$$icients are acceptable and

can be cleared at the end by multiplication.can be cleared at the end by multiplication.


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Writing and Balancing an Equation: The Combution

o! a Carbon"#$drogen"%&$gen Compound' :);+),t!)ethlene gl*ol- C6H14O4- )s +se, a a solent an,

plast)*)


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152

6 7C6H14O4 $ O2 = CO2 $ H2O

. Balance H.

2C6H14O4 $ 15O2= 12CO2 $ 14 H2O

!. Multipl" #" t$o

%. Balance O.

and chec& all elements.

Chemical E'uation:

. Balance C.

EXAMPLEEXAMPLE

C6H14O4 $ O2 = CO2 $ H2O


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&stablishing Mole!to!Mole 'atios&stablishing Mole!to!Mole 'atios

alanced chemical e!uation can be usedalanced chemical e!uation can be used

to obtain mole@to@mole relationship.to obtain mole@to@mole relationship. )C)C))77(4(4l* )5 8l* )5 8))g* (C8g* (C8 ))g* (47g* (47))8 g*8 g*


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Mass!to!Mass alculationMass!to!Mass alculation

he balanced e!uation $or a reaction andhe balanced e!uation $or a reaction and

the mass o$ any reactant or product, canthe mass o$ any reactant or product, can

be used to calculate the re!uired orbe used to calculate the re!uired or

e0pected mass o$ any other substance ine0pected mass o$ any other substance in

the e!uationthe e!uation he path 3ays 6he path 3ays 6


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E0ample6 7o3 many grams o$ AlE0ample6 7o3 many grams o$ Al))8811areare

produced 3hen +(.5 g Al react:produced 3hen +(.5 g Al react:

)Al)Alss* Fe* Fe))8811ss** AlAl))8811ss* ) Fe* ) Fell**

ANAL#Slmol1

>lg26.98

>lmol1

3232

O>lg78.45>lg41.5

O>lg!amsO>lmoles>lmoles>lg!ams

32

3232


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All reactions eventually use up a reactantAll reactions eventually use up a reactant

and stopand stop he reactant that is consumed $irst is calledhe reactant that is consumed $irst is called

thethe limiting reactantlimiting reactantbecause it limits thebecause it limits the

amount o$ product that can $ormamount o$ product that can $orm Any reagent that is not completelyAny reagent that is not completely

consumed during the reactions is said to beconsumed during the reactions is said to beinin excessexcess and is called anand is called an excessexcess

reactantreactant he computed amount o$ product is al3ayshe computed amount o$ product is al3ays

based on the limiting reagentbased on the limiting reagent

Limiting 'eactantsLimiting 'eactants


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Limiting 'eactan The HamburgerLimiting 'eactan The Hamburger


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Limiting 'eactan% #t Molecular LevelLimiting 'eactan% #t Molecular Level

CC))77++ 7 7))8 C8 C ))77558787


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1 ethylene 5 3ater became a limiting1 ethylene 5 3ater became a limiting

reactan problemsreactan problems


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E0ample6 7o3 many grams o$ N8 canE0ample6 7o3 many grams o$ N8 can

$orm 3hen 1/./ g N7$orm 3hen 1/./ g N711and +/./ g 8and +/./ g 8))

react according to6react according to6

+ N7+ N711 5 8 5 8))+ N8 7+ N8 7))88

ANAL#S


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he amount o$ product isolated $rom ahe amount o$ product isolated $rom a

chemical reactions is almost al3ays lesschemical reactions is almost al3ays lessthan the calculated, or ma0imum, amountthan the calculated, or ma0imum, amount

hehe actual yiel%actual yiel% is the amount o$ theis the amount o$ the

desired product isolateddesired product isolated hehe theoretical yiel%theoretical yiel%is the amount thatis the amount that

3ould be recovered i$ no loss occurred the3ould be recovered i$ no loss occurred the

calculated, ma0imum amount*calculated, ma0imum amount* hehe $ercentage yiel%$ercentage yiel%is the actual yieldis the actual yield

as a percentage o$ the theoretical yieldas a percentage o$ the theoretical yield

Theoritical *iel% an% Percentage *iel%Theoritical *iel% an% Percentage *iel%


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9hen 3orBing 3ith percentage yield69hen 3orBing 3ith percentage yield6"emember they involve a measured actual"emember they involve a measured actual

yield* and calculated theoretical yield*yield* and calculated theoretical yield*!uantity!uantity

he calculation may be done in eitherhe calculation may be done in either

grams or molesgrams or moles

he result can never be a number largerhe result can never be a number larger

than (//?than (//?

%100)el,pe!*entage)el,ltheo!et)*a

)el,a*t+al


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Percentage *iel%+ The Po$ ornPercentage *iel%+ The Po$ orn


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&xercise +&xercise +

%ada pembuatan asirin mengiButi reaBsi%ada pembuatan asirin mengiButi reaBsi

diba3ah, bila saat pembuatan dimulaidiba3ah, bila saat pembuatan dimulai

dengan (+.+ gr asam salisilat, dandengan (+.+ gr asam salisilat, dan

Bemudian diperoleh aspirin sebanyaB .)Bemudian diperoleh aspirin sebanyaB .)

gr aspirin. entuBan besar persentasegr aspirin. entuBan besar persentaseyield dari produB ini.yield dari produB ini.


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ki1101-2012-kd lec02b themoleandstochiometry

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