chapt05 lecture chemistry

8/9/2019 Chapt05 Lecture chemistry

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Lecture PowerPoint

ChemistryThe Molecular Nature ofMatter and Change

Fifth Edition

Martin S. Silberberg


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Chater 5

!ases and the "inetic-Molecular Theory


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!ases and the "inetic Molecular Theory

5$1 %n &'er'iew of the Physical (tates of Matter

5$2 !as Pressure and )ts Measurement

5$# The !as Laws and Their E*erimental Foundations

5$+ Further %lications of the )deal !as Law

5$5 The )deal !as Law and ,eaction (toichiometry

5$ The "inetic-Molecular Theory. % Model for !as /eha'ior

5$0 ,eal !ases. e'iations from )deal /eha'ior


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Tale 5$1 (ome )mortant )ndustrial !ases

Methane !CH"#

$mmonia !%H

Chlorine !Cl'#

()ygen !('#

*thylene !C'H"#

natural deposits+ domestic uel

rom %'H'+ ertiliers, e)plosies

electrolysis o seawater+ /leaching anddisinecting

liqueied air+ steelma0ing

high-temperature decomposition o natural gas+plastics

Name 3Formula4 &rigin and se

Atmosphere-Biosphere Redox Interconnections


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%n &'er'iew of the Physical (tates of Matter

The 1istinction o Gases rom 2iquids and 3olids

4. Gas olume changes greatly with pressure.

'. Gas olume changes greatly with temperature.

&. Gases hae relatiely low iscosity.

". Most gases hae relatiely low densities under normal conditions.

5. Gases are misci/le.


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Figure 5.1 The three states of matter$


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Figure 5.2 Effect of atmosheric ressure on o6ects

at Earth7s surface$


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Figure 5.3 % mercury arometer$


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Figure 5.4

Two tyes of

manometer

closed-end

oen-end


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Tale 5$2 Common nits of Pressure

%tmosheric Pressurenit (cientific Field

chemistryatmosphere !atm# 4 atm6

pascal !Pa#+0ilopascal !0Pa#

4.74&'5 ) 475 Pa+474.&'5 0Pa

3I unit+ physics, chemistry

millimeters omercury !Hg#

897 mm Hg6 chemistry, medicine, /iology

torr 897 torr6 chemistry

pounds per squareinch !psi or l/:in'# 4".8 l/:in'

engineering

/ar 4.74&'5 /ar meteorology, chemistry,physics

*This is an exact quantity; in calculations, we use as many significant figures as necessary


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(amle Prolem 5$1 Con'erting nits of Pressure

P,&/LEM. $ geochemist heats a limestone !CaC(## sample and collects

the C(2released in an eacuated las0 attached to a closed-endmanometer. $ter the system comes to room temperature, h;'


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Figure 5.5 The relationshi etween the 'olume

and ressure of a gas$

Boyles Law

C i ht Th M G Hill C i I P i i i d d ti di l


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Figure 5.6

The relationshi etween the'olume and temerature of a

gas$

Charless Law

C i ht Th M G Hill C i I P i i i d d ti di l


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/oyle7sLaw n and T are i)ed> 4

P

Charles7sLaw > T P and n are i)ed

>

T; constant > ; constant ) T

%montons7sLaw P T > and n are i)ed

P

T ; constantP ; constant ) T

comined gas law > T

P> ; constant )

T

P

P>

T; constant

> ) P ; constant > ; constant : P

Copyright The McGraw Hill Companies Inc Permission required or reproduction or display


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Figure 5.7 %n e*eriment to study the relationshi etween the

'olume and amount of a gas$



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Figure 5.8 (tandard molar 'olume$



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Figure 5.9 The 'olume of 1 mol of an ideal gas comared with some

familiar o6ects$

Copyright The McGraw-Hill Companies Inc Permission required or reproduction or display


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T;E )E%L !%( L% ; n@T or > ;

AoyleBs 2aw

> ;constant

P

R =PV

nT=

1 atm x 22.414 L

1 mol x 273.15 K=

0.0821 atm*L

mol*K

> ; > ;

CharlesBs 2aw

constant T

$ogadroBs 2aw

constant n

fixed n and T fixed n and P fixed P and T

Figure 5.10

R is the uni!ersal gas constant

" significant figures



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Copyright The McGraw Hill Companies, Inc. Permission required or reproduction or display.

(amle Prolem 5$2 %lying the =olume-Pressure ,elationshi

P,&/LEM. AoyleBs apprentice inds that the air trapped in a D tu/e occupies

'".= cm&

at 4.4' atm. Ay adding mercury to the tu/e, he increasesthe pressure on the trapped air to '.9" atm. $ssuming constanttemperature, what is the new olume o air !in 2#E

PL%N. (&LT)&N.

>4

in cm&

>4in m2

>4in 2

>'in 2

unitconersion

gas lawcalculation

P4; 4.4' atm P'; '.9" atm

>4; '".= cm& >'; un0nown

n and T are constant

'".= cm& 4 m2

4 cm&2

47& m2; 7.7'"= 2

P4>4

n4T4

P'>'

n'T';

P4>4; P'>'

>4P4

P'

>'; ; 7.7'"= 24.4' atm

'."9 atm; 7.7475 2

4 cm& ; 4 m2

47& m2 ; 4 2

)P4:P'



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(amle Prolem 5$# %lying the Temerature-Pressure ,elationshi

P,&/LEM. $ steel tan0 used or uel deliery is itted with a saety ale that

opens when the internal pressure e)ceeds 4.77)47&

torr. It isilled with methane at '&0C and 7.4

n4T4

P'>'

n'T';

P4

T4

P'

T';

7.


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(amle Prolem 5$+ %lying the =olume-%mount ,elationshi

P,&/LEM. $ scale model o a /limp rises when it is illed with helium to aolume o 55.7 dm&. ?hen 4.47 mol o He is added to the /limp,

the olume is '9.' dm&

. How many more grams o He must /eadded to ma0e it riseE $ssume constant T and P.

PL%N.

(&LT)&N.

Initial n4and >4as well as the inal >'are gien. ind n'and conertmoles to grams.

n4 !mol# o He

n' !mol# o He

mol to /e added

g to /e added

) >':>4

)M

su/tract n4

n4; 4.47 mol n'; un0nown

>4; '9.' dm& >'; 55.7 dm&

P and T are constant P4>4

n4T4

P'>'

n'T';

>4

n4

>'

n';

n'; n4

>'

>4 ; 4.47 mol

55.7 dm&

'9.' dm&; '.&4 mol

; ".=" g He

naddBll; n' n4; '.&4 mol 4.47 mol ; 4.'4 mol He

".77& g He

mol He4.'4 mol He



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py g p , q p p y

(amle Prolem 5$5 (ol'ing for an n>nown !as =ariale at Fi*ed

Conditions

P,&/LEM. $ steel tan0 has a olume o "&= 2 and is illed with 7.==5 0g o

('. Calculate the pressure o ('at '4o

C.

PL%N.

(&LT)&N.

>, T and mass, which can /e conerted to moles !n#, are gien.tilie the ideal gas law to ind P.

> ; "&= 2 T ; '4oC !conert to F#

n ; 7.==5 0g !conert to mol# P ; un0nown

'4oC '8&.45 ; '


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py g p , q p p y

(amle Prolem 5$ sing !as Laws to etermine a /alanced E?uation

P,&/LEM. The piston-cylinders /elow depict a gaseous reaction carried outat constant pressure. Aeore the reaction, the temperature is

457F+ when it is complete, the temperature is &77F.

PL%N.

(&LT)&N.

P and T are gien. The depiction indicates the olume doesnBt change

een though the temperature is dou/led. @elate n to T at constant P and>. *)amine equations to determine which allows or that change in n.

?hich o the ollowing /alanced equations descri/es the reactionE!4# $' A' '$A !'# '$A A' '$A'

!"# '$A' $' 'A'! $ A' $A'

2oo0ing at the relationships, the equation that shows a decrease inthe num/er o moles o gas rom ' to 4 is equation !.

n4T4; n'T' T'; 'T4 n'; J n4



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py g p q p p y

densit; m!V

n; m:M

The ensity of a !as

PV ; nRT PV ; !m:M#RT

m!V;M ) P!RT

KThe density o a gas is directly proportional to its molar mass.

KThe density o a gas is inersely proportional to the temperature.



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(amle Prolem 5$0 Calculating !as ensity

P,&/LEM. ind the density !in g:2# o C('and the num/er o molecules 3a4at3TP !7oC and 4 atm# and 34at room conditions !'7.oC and 4.77 atm#.

PL%N.

(&LT)&N.

1ensity is mass:unit olume+ su/stitute or olume in the ideal gasequation. 3ince the identity o the gas is 0nown, ind the molar mass.Conert mass:2 to molecules:2 with $ogadroBs num/er.

d; mass:olume P> ; n@T > ; n@T:P d ;@T

M) P

d;

"".74 g:mol ) 4atm

atm62

mol6F7.7='4 ) '8&.45 F

; 4.


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The Molar Mass of a !as

n@mass

M@

PV

RT

M;

M; dRTP

mRT

VPd;

m

V



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Figure 5.11

etermining the molar

mass of an un>nown

'olatile li?uid$

/ased on the method oD.A.$. 1umas !4=77-4=="#



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(amle Prolem 5$8 Finding the Molar Mass of a =olatile Li?uid

P,&/LEM. $n organic chemist isolates a colorless liquid rom a petroleum

sample. 3he uses the 1umas method and o/tains the ollowingdataL

PL%N.

(&LT)&N.

se unit conersions, mass o gas, and density-Mrelationship.

>olume o las0 ; '4& m2

Mass o las0 gas ; 8=."49 g

T; 477.7oC

Mass o las0 ; 88.=&" g

P; 85" torr

Calculate the molar mass o the liquid.

m ; !8=."49 - 88.=&"# g ; 7.5=' g

M;mRT

VP;

7.5=' g atm62mol6F

7.7='4 &8& F))

7.'4& 2 ) 7.


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alton7s Law of Partial Pressures

Ptotal; P4 P' P& ...

P4; 4) Ptotal where 4 is the mole raction

4;n4

n4 n' n&...; n4

ntotal

Mi*tures of !ases

KGases mi) homogeneously in any proportions.

K*ach gas in a mi)ture /ehaes as i it were the only gas present.



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(amle Prolem 5$9 %lying alton7s Law of Partial Pressures

P,&/LEM. In a study o ('upta0e /y muscle at high altitude, a physiologist

prepares an atmosphere consisting o 8< mole %', 48 mole 49(', and ".7 mole 4=('. !The isotope 4=( will /e measured todetermine the ('upta0e.# The pressure o the mi)ture is 7.85atm to simulate high altitude. Calculate the mole raction andpartial pressure o 4=('in the mi)ture.

PL%N.

(&LT)&N.

ind the and P rom Ptotaland mol 4=('.4=(' 4=('

mole 4=('

4=('

partial pressure P4=('

diide /y 477

multiply /y Ptotal4=('

;".7 mol 4=('

477; 7.7"7

; 7.7&7 atmP ; ) Ptotal; 7.7"7 ) 7.85 atm4=('4=('


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Figure 5.12 Collecting a water-insolule gaseous reaction

roduct and determining its ressure$



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(amle Prolem 5$1: Calculating the %mount of !as Collected o'er


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P"V"T

o gas $

amount!mol#

o gas $

amount!mol#

o gas A

P"V"T

o gas A

ideal

gaslaw

ideal

gaslaw

molar ratio rom/alanced equation

Figure 15.13

(ummary of the stoichiometric relationshis among the

amount 3molA n4 of gaseous reactant or roduct and the gas

'ariales ressure 3P4A 'olume 3V4A and temerature 3T4$



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(amle Prolem 5$11 sing !as =ariales to Find %mount of

,eactants and Products

P,&/LEM. ?hat olume o H'at 895 torr and ''5oC is needed to reduce

&5.5 g o copper!II# o)ide to orm pure copper and waterE

(&LT)&N.

PL%N. ?rite a /alanced equation. tilie stoichiometry and gas laws.

mass !g# o Cu(

mol o Cu(

mol o H'

2 o H'

diide /yM

molar ratio

use 0nown Pand T to ind >

Cu(!s# H'!g# Cu!s# H'(!g#

&5.5 g Cu(mol Cu(

8


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(amle Prolem 5$12 sing the )deal !as Law in a Limiting-,eactant

Prolem

P,&/LEM. ?hat mass o potassium chloride orms when 5.'5 2 o chlorine gasat 7.


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Postulates of the "inetic-Molecular Theory

Aecause the olume o an indiidual gas particle is sosmall compared to the olume o its container, the gasparticles are considered to hae mass, /ut no olume.

Gas particles are in constant, random, straight-linemotion e)cept when they collide with each other or withthe container walls.

Collisions are elastic, thereore, the total 0inetic energy!*0# o the particles is constant.

Postulate 4L Pa#ti$le Vol%me

Postulate 'L Pa#ti$le &otion

Postulate &L Pa#ti$le 'ollisions



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Figure 5.14 istriution of molecular seeds at three temeratures$



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Figure 5.15 % molecular descrition of /oyle7s Law$



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Figure 5.16 % molecular descrition of alton7s law of artial ressures$



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Figure 5.17 % molecular descrition of Charles7s Law$



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%'ogadro7s Law V n

(0 ; 4:' mass ) speed' (0 ; 4:' mass ) u'

u 'is the root-mean-square speed

urms; N&RTM

R; =.&4" Doule:mol6F

!raham7s Law of Effusion

The rate o eusion o a gas is inersely related to the square root o its molar mass.

rate o eusion 4

NM



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Figure 5.18 % molecular descrition of %'ogadro7s Law$



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Figure 5.19 ,elationshi etween molar mass and molecular seed$

(0; &:'!R:)$# T


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Figure 5.20 iffusion of a gas article through a

sace filled with other articles$

distri/ution o molecular speeds

mean ree path

collision requency



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Figure B5.1

=ariations in ressureA temeratureA and

comosition of the Earth7s atmoshere$

=ariations in ressureA temeratureA and comosition of

the Earth7s atmoshere



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Tale 5$+ Molar =olume of (ome Common !ases at (TP

3:oC and 1 atm4

!as

Molar =olume

3LBmol4

Condensation Point

3oC4

HeH'

%e)deal gas

$r%'('

C(Cl'%H&

''."&5''."&'

''."''22$+1+

''.&


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Figure 5.21

The eha'ior of se'eral

real gases with

increasing e*ternal

ressure$



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Figure 5.22 The effect of intermolecular attractions on

measured gas ressure$



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Figure 5.23 The effect of molecular 'olume on measured gas 'olume$


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chapt05 lecture chemistry

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