Post on 01-Jun-2018
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DEAL GASES
Louie Paolo D. CarpioInstructor 3
Institute of Chemistry, UP Diliman
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OBJECTIVES for today
1. Define gases
2. Define different variables of a gas
3. Define an ideal gas
4. Define and apply gas laws
5. Discuss Kinetic olecular !"eoryof gases
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S I!!S that you "ill need
1. #olving ideal gas e$uations
2. #olving gas laws
3. #toic"io%etry involving gases
4. Kinetic %olecular t"eory proble%s
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#!&!'# () &!!'*
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+,- #! D- /'#0
# /'# would be an ideal %odel to
describe t"e inetic be"avior of%olecules.
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P*(P'*! '# () /'#
# /ases "ave no definite s"ape.# /ases "ave no definite volu%e.
# /ases enclosed in a non rigidcontainer would "ave varying volu%esdepending on t"e conditions.
# /ases are capable of e panding orcan be easily co%pressed.
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D'#C* 6/ & /
/'# C&6 ' D'#C* 'D - 3 C &C*(#C(P C 7&* & L'#8
1. 7(L '2. P*'## *'
3. !' P'*&! *'
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7(L ' () & /
7(L ' 9 a%ount of space occupied
Conventional unit in c"e%istry liters
Derived #. . unit in c"e%istry 9 % 3
1 liter : 1;;; %L : 1;;; c% 3 : 1 d% 3
1 liter : ;.;;1 % 3
Conversion factors8
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P*'## *' () & /
P*'## *' 9 a%ount of force per unitareaConventional unit in c"e%istry at%
Derived #. . unit in c"e%istry 9 Pa
1 at% : 1;1325 Pa : 1.;1325 bar
1 at% :
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P*'## *' () & /
P*'## *'
a%ount of force per unit
area$ &verage force e erted by agas on t"e walls of t"e
container $ %easured using abaro%eter or a %ano%eter
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!' P'*&! *'
!' P'*&! *' >uantitative description of t"e
average inetic energy of %olecules
Conventional unit in c"e%istry Kelvin
K :(
C ? 2
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D'&L /
D'&L /
$ Perfect gas
$ ndividual gas %olecules do not
attract repel nor react wit" one anot"er $ energy and %o%entu% duringcollisions wit" ot"er gas %olecules are
conserved$ gases e "ibit t"is be"avior at lowpressures and "ig" te%peratures
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D'&L / & (D'L
)or general c"e%istry purposes allcalculations assu%e t"at gases "aveideal c"aracteristics unless statedot"erwise.
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D'&L / '> &! (6
)or an ideal gas its %acroscopicvariables are related by t"e e$uation
+"ereP : pressure in at%
7 : volu%e in liters
n : nu%ber of %oles of gases
* : gas constant : ;.; 21 @LEat%AB@%ol EKA
! : te%perature in Kelvin scale
P 7 : n * !
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&L!'*6&! 7' D'&L/ '> &! (6
+"ereP : pressure in at%
gas : %olar %ass of gas in gB%ol
d : density of gas in gBL
* : gas constant : ;.; 21 @LEat%AB@%ol EKA
! : te% erature in Kelvin scale
P gas : d * !
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#!P C(6D ! (6#
#!&6D&*D !' P'*&! *' &6DP*'## *'
! : 2
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#!&6D&*D (L&* 7(L '
7(L ' of 1 %ole of anyideal gas in #!P Conditions
@1 at% and 2
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'F& PL'
2.;; %oles of an ideal gas "as apressure of 5.2; at% at 45; K.Co%pute for t"e volu%e and %olar%ass of t"is ideal gas if t"e %ass oft"e gas was found to be 4. gra%s.
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'F& PL'Co%plete t"e table below for gaseous
6 2( 4 @ 6 2( 4 : G2.;2 gB%olA
105(F)390 K 1.15 L(E)
(D)0.783(C)488 mL673 mm
Hg
(B)(A)43.1 oC4.98 L1.77 atm
gramsnTVP
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#!( C, ( '!*- involving gases
%ass %olar
substance of gra%sn =
( )Kliters gasDat% gasD
!*7Pn =
1. substance
3. solute in solHn
5. ideal gas
( ) ( )litersnDsolInsolI 7n =
)or%ula to solve fort"e nu%ber of %oles!ype of reactant
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/ L&+#8
1. oyleHs Law2. C"arlesHs Law
3. /ay LussacHs Law
4. &vogadroHs Law
5. Co%bined /as Law
=. DaltonHs Law of Partial Pressures
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%as la"s
1. oyleHs law 9 at constant ! t"evolu%e of a gas is inverselyproportional to t"e applied pressure.
V &'(P)
or
P17
1 : P
27
2
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%as la"s
2. C"arlesHs law 9 at constant P volu%eis directly proportional to te%perature
7 !
or
2
2
1
1!7
!7
=
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Deri*ation of the el*in scale
&bsolute scale 9 Kelvin scale
&bsolute ero 9 te%perature at w"ic"t"ere is ero volu%e @( K : 2
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%as la"s
3. /ay LussacHs law 9 at constant 7pressure is directly proportional tote%perature
P Tor
2
2
1
1!P
!P
=
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%as la"s
4. Co%bined gas law e$uation 9co%bination of t"e t"ree previous gaslaws as long as no gas escapes t"econtainer @constant n or %oles of gasA
2
22
1
11
!7P
!7P =
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'F& PL'
/aseous 6, 3 at 2;; oC e erts apressure of 3.45 at% in a 3 .G literballoon. f t"e te%perature was
decreased to 15;o
C and t"e pressurewas relieved to 2.;; at% calculatet"e volu%e of t"e balloon containing6, 3.
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%as la"s
5. &vogadroHs law 9 at constantte%perature and pressure t"e nu%berof particles of a gas is directlyproportional to its volu%e
7 n
or
2
2
1
1
n7
n7 =
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%as la"s
=. DaltonHs law of Partial pressures 9 atconstant te%perature and volu%e t"epressure of a gas is directly
proportional to its nu%ber of %oles
P n
or
2
2
1
1
nP
nP =
n321total.....PPPPP +++=
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0O!E .+ CTIO-
(L' )*&C! (6 @ A %ole fraction ofof a co%ponent in a %i ture can bedescribed by t"e e$uation8
111+++== 3211
total
11 nnn
nn
nM
1=+++= 111321n MMMM
n a %i ture t"e %olefractions add up to 1
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P +TI ! P+ESSU+ES
P&*! &L P*'## *' pressure e erted by a gas in a%i ture of gases
Depends on its %ole fraction in t"e%i ture
( )'total' 2PP =
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% S CO!!ECTED OVE+ TE+
#ince water evaporates even below itsboiling point pressure of t"e watervapor %ust be accounted w"en a gas iscollected over water.
vapor water totalgas PPP =
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% S CO!!ECTED OVE+ TE+
$' a%ple sam4le of hydro5en "ascollected 6y dis4lacement of "ater at 7819oC1 The atmos4heric 4ressure "as :;
( ) torr
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&L!'*6&! 7' #!( C, ( '!*- in/'#
7 %oles of a gas
P %oles of gas
&vogadroHs law @constant ! and PA
7olu%e ratios instead of%ole ratiosN
DaltonHs law @constant ! and 7A
Partial pressure ratiosinstead of %ole ratiosN
/ay LussacHs Law of
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/ay LussacHs Law ofCo%bining 7olu%es
!"e %ole ratios of gaseous substancesin a c"e%ical reaction can also bee pressed in t"e sa%e volu%e ratios
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'F& PL'
,ow %any liters of a%%onia arere$uired to c"ange 12.1 liters of 6(to 6 20 &ssu%e 1;;O yield and t"e
reaction was done under constant !and P.
4 6, 3@gA ? = 6( @gA 5 6 2@gA ? = , 2( @lA
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'F& PL'
n a 1.;; liter container and 2;; oC acertain a%ount of 6 2 gas would e erta pressure of ;.;3= at%. & certaina%ount of , 2 gas would e ert a
pressure of ;.12; at% in t"e sa%econtainer. +"at would be t"e finalpressure in t"e 1.;; liter container if
t"e gaseous 6 2 and , 2 wereco%bined and allowed to react tofor% gaseous 6, 30
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K NET C MOLECULAR
THEORY OF GASES
Louie Paolo D. CarpioInstructor 3
Institute of Chemistry, UP Diliman
# &*- () K 6'! C
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# & - () K 6 ! C(L'C L&* !,'(*- () /'#
1. /ases are %ostly e%pty space.2. /as %olecules are in constant
c"aotic %otion.
3. Collisions are elastic @energy and%o%entu% is conservedA
4. /as pressure is caused by t"ecollisions of t"e %olecules wit"t"e walls of t"e container.
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' pression for Pressure
6 : of %oleculesu : average speed
: %ass of %olecule
7 : volu%e of container
376 uP
2=
# !"e pressure is directly proportionalto speed of t"e gas.
# Pressure is inversely proportional tovolu%e.
&verage Kinetic 'nergy of
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&verage Kinetic nergy of!ranslational otion
6 & : =.;2 1; 23
! : te%perature in K
* : .314 QB%olEK
&t 26
3*!' =
# 'nergy is directly proportional tote%perature
# 'nergy is independent of %ass at t"esa%e te%perature
&verage #peed of /ases
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&verage #peed of /ases
# The ?inetic ener5y of the molecules is4ro4ortional to the a6solute tem4erature1The ?inetic ener5y of the molecules is4ro4ortional to the a6solute tem4erature1
# Dis4layed in a 0a="ellian distri6ution1
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&verage #peed of /ases
: %olar %ass of gas
! : te%perature in K
* : .314 QB%olEK
3*!R =
# #peed is directly proportional to t"es$uare root of te%perature
# #peed is inversely proportional to t"es$uare root of t"e %olar %ass
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*elative #peeds of /ases
== 12
2
1
2
2
1
1
2
1
!!
3*!
3*!
RR
/iven two gases t"eir relative speedscan be derived8
# #peed is directly proportional to t"es$uare root of te%perature
# #peed is inversely proportional to t"es$uare root of t"e %olar %ass
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%as la" from the 0T
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'F& PL'
Co%pare t"e speeds of ( 3 andgaseous ,Cl. +"ic" is faster0' press t"e speed of ,Cl in ter%s of
t"e speed of ( 3.( 3 9 4 .;; gB%ol ,Cl 9 3=.4= gB%ol
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REAL GASES
Louie Paolo D. CarpioInstructor 3
Institute of Chemistry, UP Diliman
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*'&L /'#
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*'&L /'#
)ro% a %olecular standpointdeviations fro% t"e ideal gas lawarise because it neglects two
factors82. attractive forces between gases
3. t"e finite volu%e of gas particles
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olar 7olu%e
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olar 7olu%e
Definition 9 t"e volu%e of 1 %ole of gas
Denoted by t"e sy%bol 7 %
n
7 7
% =
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'ffect of &ttractive )orces
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ffect of &ttractive )orces
;7
77o
%
o%% &! (6#
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(!, &L / &! (6#
*edlic" Kwong e$uation of state
Peng *obinson e$uation of state
(!,'* *'&L / '> &! (6#
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(!, &L / &! (6#
Dieterici e$uation of state
7irial '$uation of state
'6D () CL#
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6D () C &
# C"apter covered8 C"apter 12
# 6e t %eeting8 !"er%odyna%ics
# > '#! (6#0000