5. ap chapt 5 gases

8/13/2019 5. AP Chapt 5 Gases

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GasesChapter 5

Properties of gases and gas laws.


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What does this show about gases?Why?


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Kinetic Molecular Theory

The KMT explains what happens to gases on a molecular level and assumesthat

1. Gas particles are point masses (have negligible volumesince the distance between molecules is !"# greater.

$. The particles are in rapid% random% constant straight linemotion. "ll collisions are perfectl& elastic (no energ& is lost.

'. There are ) attractive or repulsive forces betweenparticles.

*. The average +inetic energ& is directl& proportional totemperature according to the e,uation

K-avg/mu$

where u$average mean s,uare speed '#T0M

molar mass


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Temperature and Molecular Speed

Higher

temperature

will shift

average

molecular

speed to the

right


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Physical Characteristics of Gases

Gases have high +inetic energ& and

a. have no definite volume or shape

(compressible.

b. assume the shape and volume of their

containers.

c. there is much space betweenmolecules (ver& low densit&.


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What is pressure?

Pressure is a force per unit area. !or gases%pressure comes from the pounding ofmolecules against each other and the walls of

the container.2hat will affect pressure3 4ncreasing temperature and concentration will

increase pressure% and decreasing volume(s,uee5ing will increase pressure.

6-M) 2hat causes pressure in theatmosphere3 2h& doesn7t water in a test tubefall out when inverted3


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ow is pressure measured?

"tmospheric pressure is measured with a

barometer.

2h& is mercur& used3 8impl& because it has a

high densit& (1'.9 g0m:% so the barometer can

be small.Which gas has the

highest pressure? How

would the tubes look if

the gases inside were at


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Gas pressure using a manometer

" manometer is used to measure pressure of

gases other than at atmospheric pressure.

CASE 1 gaspressure e!uals

atm pressure"#gas

$ #atm%

CASE & gaspressure is greater

than atm pressure"#gas$ #atm ' #h%

CASE ( gaspressure is less

than atm pressure"#gas$ #atm ) #h%


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Temperature and Pressure ofGases

The average +inetic energ& of all the

molecules is proportional to the temperature.

Pressureis the force of the collisionsbetween the gas particles and the sides of the

container.

The volume of a gas(!% the number of gasparticles in that volume(n% the pressure of

the gas(P% and the temperature of the gas(T

are variables that depend on one another.


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Standard Temperature andPressure of Gases

8tandard atmospheric pressure

"#"$%&5 'Pa ( " atm ( )*# torr ( )*# mm g

8tandard temperature #+C ( &)% K

2e indicate that a gas has been measured

at standard conditions b& the capital lettersSTP(standard temp. and atm. pressure

E*periments show that at S+#, 1 mole of an


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Pressure ,nits and Con-ersions

There are four different units of pressure

used in chemistr&. ;ere the& are

1 atmospheres (atm$ millimeters of mercur& (mm;g

' Torr

* +iloPascals (+Pa

1 atm = 101.3 kPa = 760.0 mmHg = 760.0 torr


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Sample Problems.

-x


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Con-erting /etween ,nits ofTemperature

A -B-#C T-MP-#"TD#- D8-6 4 "G"8 :"2


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/oyle1s 2aw

#obert Eo&le% a

Eritish chemist%examined the

relationship between

volumeand pressureof gases.


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/oyle1s 2aw

If the amount (n)

and the

temperature (T) ofa gas remain

constant, the

pressure exerted

by the gas varies

inversely as the

volume.

Hg

added,

pressureincr-


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/oyle1s 2aw


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3pplying /oyle1s 2aw

-x " gas is collected and found to fill $.?= :

at $*= +Pa. 2hat will be its volume at

standard pressure34solate B$ P1B1 P$B$

P1B1 P$B$

P$ P$

P1B1 B$

P


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Charles1s 2aw

Jac,ues


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Charles1s 2aw

The volume of a

quantity of a gas,held at a constant

pressure, varies

directly with the

elvin

temperature.


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Charles1s 2aw


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Charles1s 2aw and 3bsolute 7ero


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,sing Charles1s 2aw8 we can

deri-e the following e9uation.

!"

:T"

( !&

:T&


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3pplying Charles1s 2aw

-x" gas is collected and found to fill $.?=

: at $=.>


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More Charles1s Problems constant P6

1*.*> : of a gas is collected at =>.>>. K

' >: at $>.> < is compressed to 1.>> :.

"8 1*@ K


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,sing the Combined Gas 2aw.


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Combined Gas 2aw Problems

"6 3 gas has a -olume of ;##$# m2 at minus &%$## +Cand %##$# torr$ What would the -olume of the gas beat &&)$# +C and *##$# torr of pressure?

3>S. ;##$ m2

&6 5##$# liters of a gas are prepared at )##$# mm g and#$# +C$ The gas is placed into a tan' under highpressure$ When the tan' cools to $# +C8 thepressure of the gas is %#$# atm$ What is the -olume ofthe gas?

3>S. =$5" 2

%6 The pressure of a gas is reduced from "#$# mm gto ;5#$# mm g as the -olume of its container isincreased by mo-ing a piston from ;5$# m2 to %5#$#m2$ What would the final temperature be if theoriginal temperature was =#$# +C?

3>S. "#*# K


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3-ogadro1s 2aw

The volume of a gas

maintained atconstant temperature

and pressure is

directly proportional

to the number of

moles of the gas.


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Dsing "vogadro7s :aw% we can derive the

following e,uation

!":n"( !&:n&


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So, what is the volume for an8 gas at S+#? &&-. /9mol:


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,sing 3-ogadro1s 2aw

-x " balloon isfilled with $.>moles of ;elium

gas% occup&ing**.? : at constanttemp. ;ow man&liters will beoccupied if thenumber of molesis reduced to 1.=3

4solate un+nown

B10n1 B$0n$

B$ n$B10n1

**.? : x 1.= mol

$.> mol

''.9 :


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The deal Gas @9uation

2hen we combine Eo&le7s%


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,sing the deal Gas 2aw.


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More deal Gas Problems

1 " sample of mol

$ " flashbulb contains $.* x1>*moles of )$

gas at a

pressure of $.>1 +Pa and a temperature of 1I


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Calculating Bensity and Molar Mass

2e can use the ideal gas e,uation to

calculate gas densit&.

6ensit& has the units g0: so we rearrange thee,uation to

n LPL

B #Tow the units on the left are moles0: so we

can multipl& each side m& molar mass (units

g0mole..


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nM PM

B #T

moles cancel leaving units of g0:(densit&.

Thus% ddensity6 ( PM

AT#earranged% M molar mass6 ( dAT

P

C l l t th d iti f > d t


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Calculate the densities of >&and e at

STP4using the gas density e9uation.


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Bensity and Molar Mass Problems

2hat is the densit& of carbon tetrachloride vapor

at @1* torr and 1$=.?$I g0:

2hat is the molar mass of a substance that has adensit& of $.== g0: at a pressure of @?= torr and

temperature of *=


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Balton s 2aw ofPartial Pressures

)ur calculations so far have been for pure

gases. John 6alton formed a h&pothesis about

pressure exerted b& a mixture of gases.

6alton7s :aw of Partial Pressure The total

pressure in a container is the sum of the partial

pressures of all the gases in the container.

Ptotal( P"0 P&0 P%4

' $'
http://en.wikipedia.org/wiki/Image:Johndalton.jpg


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;alton


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Consider a case in which two gases, Aand =, are in a

container of volume >-

PA$nA+

V

P=$nB+

V

nAis the number of moles of A

n=is the number of moles of =

P+$PA'P= XA$nA

nA' n=

X=$n=

nA' n=

PA$xAP+ P=$x=P+

Pi$xiP+


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Gas Mi


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Partial Pressure of 3ir

"ir is an example of a mixture of gases.

nitrogen is @?.>?* ox&gen is $>.I*?

argon is >.I'*

carbon dioxide is >.>'1=

neon% helium% +r&pton% and xenon are

among the other trace gases.


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Gases in air

Wh t i th ti l f


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What is the partial pressure ofo torr. 4f @? of air is nitrogen%

then @? of pressure is due to nitrogenmolecules.

>.@? x @9> torr =I' torr

$1 of air is ox&gen so $1 of pressureis due to ox&gen molecules.

>.$1 x @9> torr 19> torr

C ll ti G b W t


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Collecting Gases by WaterBisplacement

)ne method to collect gases is b& water

displacement.

Gases must be insoluble in water.2hen collection is complete% water vapor

is present in the collection container and

must be accounted for in the partialpressures of gases.


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&@Cl( "s% &@Cl "s% ' (& "g%

Bottle full of oxygen gas and water vapor

P+ $P 'PH &&

d t f


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ow do you correct for -aporpressure of water?

Bolume of a dr& gas

Pgas( Ptotal Pwater

-x " ,uantit& of gas is collected over

water at ?< in a >.'=' : vessel at ?*.=

+Pa. 2hat volume would the dr& gas

occup& at standard atmosphericpressure and ?


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Continued4

P1B1 P$B$

P1B1 B$

P$

?'.* +Pa x >.'=' : $I1 :

1>1.' +Pa


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Partial Pressure Practice Problem

" gas is collected over water and occupies a

volume of =I9 cm'at *'1.1 +Pa. 2hat volume will the dr& gas occup&

at *'< and standard atmospheric pressure3 Thevapor pressure of water at *'< is ?.9 +Pa.

"8 =*= m:


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Biffusion and Graham1s 2aw

Kinetic theor& states that molecules travel in

straight lines. Molecules often collide with other

molecules which alters its path and sends it on

another straight path. This is the basic idea of diffusion. "s gas

molecules diffuse% the& become more and

more evenl& distributed throughout theircontainer. http00highered.mcgrawhill.com0sites0>>@$*I=?==0studentLview>0chapter$0animationLLhowLdiffusio
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html


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ow is effusion different from


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ow is effusion different fromdiffusion?

Aelationship between mass and


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Aelationship between mass andrate of diffusion

Dsing Graham7s :aw% we can derive

r" ( DM&D

r&

M"


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Be-iations from deal Gas /eha-ior

2hen using the ideal gas e,uation% two

assumptions were made

1. Gas particles have novolume.$. Gas particles have noattractive forces

between them.

2e will now examine how real gases candeviate from these assumptions.

ow are real gases different from ideal?


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"ssumption 1 Gases occup& no volume. "t low pressures% both ideal and real gases

are far apart% separated b& empt& space. "s pressure is applied% real gases begin to

ta+e up more of the empt& space. 4dealgases are still far apart.

"n ideal gas can have 5ero volume% but areal gas will become a li,uid underincreased pressure.



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"ssumption $ Gases have no attractive forcesbetween them.

4f gases are made up of polar molecules such

as water% the attractive forces are large and thebehavior of this real gas is mar+edl& differentfrom an ideal gas.

There are even wea+ attractive forces(dispersion forces between noble gases.

!or most gases% the ideal gas laws areaccurate to about 1.


What does this show about the effect of intermolecular forces on the

t d b


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pressure e*erted b8 a gas-

;eviations from deal =ehavior


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no gas behaves ideall8- =ehavior becomes

less ideal at high pressures

1 mole of ideal gas

PV$ nRT

n =PV

RT$ 1-3

epulsive Dorces

Attractive Dorces


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Scuba Chemistry.
http://www.scubadiving.com/learntodive/dive_into_adventure/one_big_adventure


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Scuba Chemistry.The /ends

"s divers sin+ down to high pressure water (pressure

doubles at 1> m or '' ft% the air that the& breathe

becomes more soluble in their blood.

6ecompression sic+ness% or Nthe bendsO occurs asdivers rise to the surface% the pressure decreases% and

bubbles of gas suddenl& form in the bloodstream as

the gas becomes less soluble.

6ecompression sic+ness% also +nown as the bends% is

one danger of diving. )ther dangers include nitrogen

narcosis% ox&gen toxicit& and simple drowning (if &ou

run out of air before ma+ing it bac+ to the surface.
http://www.scubadiving.com/learntodive/dive_into_adventure/one_big_adventure


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Barwin 3ward Winner "===4+he Asaka =eer corporation brews Suiso brand beer, in which the carbon

dio*ide normall8 used to add fi77 has been replaced b8 the more

environmentall8 friendl8 h8drogen gas- +wo side effects of the h8drogen gas

have made the beer e*tremel8 popular at karaoke sing)along bars and clubs-

Dirst, because h8drogen molecules are lighter than air, sound waves are

transmitted more rapidl8, so individuals whose lungs are filled with the

nonto*ic gas can speak with an uncharacteristicall8 high voice- E*ploiting this

!uirk of ph8sics, chic urbanites can now sing soprano parts on karaoke sing)

along machines after consuming a big gulp of Suiso beer-


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CE& emissions


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ncoming Solar Aadiation


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Greenhouse Gases A Spectra

"tmospheric

gases that

trap infrared

heat.

THE END


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THE END


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WarmFup. What1s the o'e?

8everal &ears ago% a scientific publication reported

that one of their readers% while attending a

scientific conference% overheard two colleagues

discussing a paper that had been presented. 4n allseriousness% one said to the other something to

the effect that% N;e reported that the internal

temperature of the 8un was about 1= million

degrees% but 4 don7t remember whether that was in&E6 and


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Warm up. f laughing gas >&E6 andC> were released4$

5. ap chapt 5 gases

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