18
Gases Chapter 8 Chapter 8 8 8.1 - Properties of Gases 8.2 – Pressure and Volume (Boyle’s Law) 8.3 – Temperature and Volume (Charles’ Law) 8.4 – Temperature and Pressure (Guy-Lussac’s Law) 8.5 – The Combined Gas Low 8.6 – Volume and Moles (Avogadro’s Law) 8.7 – The Ideal Gas Law 8.8 – Partial Pressures (Dalton’s Law) 8.1 Properties of Gases Goal: Describe the Kinetic Molecular Theory of Gases and the units of measurement used for gases. Gases We are surrounded by gases, but we are often unaware of their presence. Of the elements on the periodic table, only a handful are gases at room temperature: H 2 , He, N 2 , O 2 , F 2 , Cl 2 , and the noble gases. Other common gases are molecules with oxygen and small nonmetals: CO, CO 2 , NO, NO 2 , SO 2 , SO 3 Generally, molecules that are gases at room temperature have fewer than 5 atoms and are from the 1 st and 2 nd period.

Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

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Page 1: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Gas

esC

hap

ter

8

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Lo

w8

.6 –

Vo

lum

e an

d M

ole

s (A

voga

dro’

s La

w)

8.7

–T

he

Idea

l Gas

Law

8.8

–P

arti

al P

ress

ures

(Dal

ton’

s La

w)

8.1

Pro

per

ties

of G

ases

Go

al: D

escr

ibe

the

Kin

etic

Mo

lecu

lar

Th

eory

of G

ases

and

th

e un

its

of m

easu

rem

ent

used

fo

r ga

ses.

Gas

esW

e ar

e su

rro

un

ded

by

gase

s, b

ut

we

are

oft

en

un

awar

e o

f th

eir

pres

ence

.

Of t

he

elem

ents

on

th

e p

erio

dic

tab

le, o

nly

a h

and

ful

are

gase

s at

ro

om

tem

pera

ture

: H2

, He,

N2

, O2

, F2

, C

l 2, a

nd

th

e n

ob

le g

ases

.

Oth

er c

om

mo

n g

ases

are

mo

lecu

les

wit

h o

xyge

n a

nd

sm

all n

on

met

als:

CO

, CO

2, N

O, N

O2

, SO

2, S

O3

Gen

eral

ly, m

ole

cule

s th

at a

re g

ases

at

roo

m

tem

pera

ture

hav

e fe

wer

th

an 5

ato

ms

and

are

fro

m

the

1st

and

2n

dpe

rio

d.

Page 2: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Gas

esT

he

beh

avio

r o

f gas

es is

qu

ite

dif

fere

nt

fro

m t

hat

of

liqu

ids

and

so

lids.

×G

as p

arti

cles

are

far

apar

t, w

her

eas

par

ticl

e o

f b

oth

liq

uid

s an

so

lids

are

hel

d c

lose

to

geth

er.

×A

gas

has

no

def

init

e sh

ape

or

volu

me

and

will

co

mp

lete

ly fi

ll an

y co

nta

iner

.

×B

ecau

se th

ere

are

grea

t d

ista

nce

s b

etw

een

gas

pa

rtic

les,

a g

as is

less

den

se t

han

a s

olid

or

liqu

id

and

eas

y to

co

mp

ress

.

Kin

etic

Mo

lecu

lar

Th

eory

of G

ases

1. A

gas

co

nsis

ts o

f sm

all p

arti

cles

(ato

ms

or

mo

lecu

les)

that

m

ove

ran

dom

ly w

ith

h

igh

vel

oci

ties

.

Gas

mo

lecu

les

mo

vin

g in

ran

do

m

dir

ecti

on

s at

hig

h

spee

ds

cau

se a

gas

to

fi

ll th

e en

tire

vo

lum

e o

f a c

on

tain

er.

2. T

he

attr

acti

ve

forc

es b

etw

een

the

par

ticl

es o

f a g

as a

re

usu

ally

ver

y sm

all.

Gas

par

ticl

es a

re f

ar

apar

t an

d f

il a

con

tain

er o

f an

y si

ze

and

sha

pe.

3. T

he

actu

al v

olu

me

occ

upie

d b

y ga

s m

ole

cule

s is

ex

trem

ely

smal

l co

mp

ared

wit

h th

e vo

lum

e th

at th

e ga

s o

ccup

ies.

Th

e vo

lum

e o

f th

e ga

s is

con

sid

ered

eq

ual t

o t

he

volu

me

of t

he

con

tain

er.

Mo

st o

f th

e vo

lum

e o

f a g

as is

em

pty

sp

ace,

whi

ch a

llow

s ga

ses

to b

e ea

sily

co

mp

ress

ed.

Kin

etic

Mo

lecu

lar

Th

eory

of G

ases

4. G

as p

arti

cles

are

in c

on

stan

t m

oti

on, m

ovi

ng

rap

idly

in

stra

igh

t pat

hs.

Wh

en g

as p

arti

cles

co

llid

e, t

hey

re

bo

un

d a

nd

tra

vel i

n n

ew

dir

ecti

on

s.

Eve

ry t

ime

they

hit

th

e w

alls

of

the

cont

ain

er t

hey

exe

rt

pre

ssur

e.

An

incr

ease

in t

he

nu

mb

er o

r fo

rce

of c

olli

sio

ns

agai

nst

th

e w

alls

of t

he

con

tain

er c

ause

s an

in

crea

se in

th

e pr

essu

re o

f th

e ga

s.

5. T

he

aver

age

kin

etic

en

ergy

of

gas

mo

lecu

les

is p

rop

ort

ion

al to

th

e te

mp

erat

ure

in K

elvi

n.

Gas

mo

lecu

les

mo

ve f

aste

r as

th

e te

mp

erat

ure

incr

ease

s.

At

hig

her

tem

per

atu

res,

gas

m

ole

cule

s h

it t

he

wal

ls o

f th

e co

nta

iner

mo

re o

ften

an

d w

ith

m

ore

fo

rce,

pro

du

cin

g h

igh

er

pres

sure

s.

SSmel

lsW

e ca

n q

uic

kly

smel

l pe

rfu

me

wh

en a

bo

ttle

is

ope

ned

acro

ss t

he

roo

m

bec

ause

its

part

icle

s m

ove

ra

pid

ly in

all

dir

ecti

on

s.

At r

oo

m t

emp,

air

mo

lecu

les

mo

ve a

t 1

00

0 m

ph

.

App

licat

ion

s

Exp

losi

ons

Som

etim

es ti

res

or

gas-

fille

d c

on

tain

ers

expl

od

e w

hen

tem

pera

ture

s ar

e to

o

hig

h.

Fro

m th

e K

MT

, we

kno

w

that

gas

par

ticl

es m

ove

fast

er w

hen

hea

ted,

hit

th

e w

alls

of a

co

nta

iner

wit

h

mo

re fo

rce,

an

d c

ause

a

build

up o

f pre

ssur

e in

side

a

con

tain

er.

Th

e ki

neti

c m

ole

cula

r th

eory

hel

ps e

xpla

in e

very

day

thin

gs:

Page 3: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Wh

en w

e ta

lk a

bo

ut a

gas

, we

des

crib

e it

in t

erm

s o

f 4 p

rope

rtie

s:

Pre

ssu

reV

olu

me

Tem

per

atu

reA

mo

un

t

Pre

ssu

re (P

)G

as m

ole

cule

s ar

e ex

trem

ely

smal

l an

d m

ove

ra

pid

ly.

Wh

en t

hey

hit

th

e w

alls

of

a co

nta

iner

, th

ey e

xert

p

ress

ure.

If w

e h

eat

the

con

tain

er,

the

mo

lecu

les

mo

ve fa

ster

an

d s

mas

h in

to t

he

wal

ls

mo

re o

ften

an

d w

ith

in

crea

sed

forc

e, t

hu

s in

crea

sin

g th

e p

ress

ure

.

Co

mm

on

un

its:

×

atm

osp

her

es (a

tm)

×m

m o

f mer

cury

(m

mH

g)

×in

of m

ercu

ry (i

nH

g)

×P

asca

ls (P

a)

×to

rr

×po

un

ds

per

squ

are

inch

(psi

)

Vo

lum

e, T

emp

erat

ure

, Am

ou

nt

Vo

lum

e (V

)

Th

e vo

lum

eo

f a g

as

equ

als

the

size

of

the

con

tain

er in

w

hic

h t

he

gas

is

pla

ced

.

Un

its:

L, m

L

Tem

pera

ture

(T)

Th

e te

mpe

ratu

reo

f a

gas

is r

elat

ed t

o

the

kin

etic

en

ergy

of

its

part

icle

s.

Kin

etic

En

ergy

–en

ergy

of m

oti

on

.A

s p

arti

cles

mo

ve

fast

er, t

hey

ge

ner

ate

mo

re

kin

etic

ene

rgy

in t

he

form

of h

eat.

Un

its:

Kel

vin

(no

n

egat

ive

num

bers

)

Am

ou

nt o

f gas

(n)

Th

e am

oun

t of g

as

refe

rs t

o th

e m

ass

of

the

gas

pre

sen

t.

Un

its:

gra

ms

or

mol

es

(mol

es a

re u

sed

in

equ

atio

ns)

12

Page 4: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

13

Con

vert

4820

mm

Hg

to a

tmos

pher

es. (

1 at

m=

760

mm

Hg)

Con

vert

48 p

si to

torr

(14.

7 ps

i = 1

atm

= 76

0 m

mH

g)C

hap

ter

888

.1 -

Pro

pert

ies

of G

ases

8.2

–P

ress

ure

and

Vo

lum

e (B

oyle

’s L

aw)

8.3

–T

empe

ratu

re a

nd

Vo

lum

e (C

harl

es’ L

aw)

8.4

–T

empe

ratu

re a

nd

Pre

ssur

e (G

uy-L

ussa

c’s

Law

)8

.5 –

Th

e C

om

bine

d G

as L

ow

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

Page 5: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

8.2

Pre

ssu

re a

nd

Vo

lum

e (B

oyl

e’s

Law

)G

oal

: Use

th

e p

ress

ure-

volu

me

rela

tio

nshi

p (

Boy

le’s

Law

) to

det

erm

ine

the

fin

al p

ress

ure

or

volu

me

wh

en t

he

tem

per

atu

re a

nd

am

ou

nt

of g

as a

re c

on

stan

t.

Pre

ssu

re a

nd

Vo

lum

eIm

agin

e th

at y

ou

can

see

air

par

ticl

es

hit

tin

g th

e w

alls

insi

de

a b

icyc

le t

ire

pu

mp

.

Wh

at h

appe

ns

to t

he

pre

ssu

re in

sid

e th

e pu

mp

as y

ou

pu

sh d

ow

n o

n t

he

han

dle

?

As

the

volu

me

dec

reas

es, t

he

air

mo

lecu

les

are

cro

wd

ed t

oge

ther

. Mo

re

colli

sio

ns

occ

ur

wit

h t

he

wal

ls, i

ncr

easi

ng

the

pre

ssu

re.

P a

nd

V –

Inve

rse

Rel

atio

nsh

ip

Wh

en a

ch

ange

in o

ne

pro

per

ty c

ause

s a

chan

ge in

an

oth

er, t

he

two

pro

pert

ies

are

said

to

be

rrela

ted.

If t

he

chan

ges

occ

ur

in o

ppo

site

dir

ecti

on

s, th

e pr

ope

rtie

s ar

e in

vers

ely

rela

ted.

Th

e in

vers

e re

lati

onsh

ip b

etw

een

P a

nd

V is

kn

ow

n a

s B

oyl

e’s

Law

.

P a

nd

V –

Bo

yle’

s La

wBB

oyl

e’s

Law

: th

e vo

lum

e (V

) of a

sam

ple

of a

gas

ch

ange

s in

vers

ely

wit

h t

he

pre

ssu

re (P

) of t

he

gas

as lo

ng

as t

her

e is

no

ch

ange

in t

he

tem

pera

ture

(T) o

r am

ou

nt o

f gas

(n)

A r

esu

lt o

f Bo

yle’

s La

w is

th

e eq

uat

ion

:

P1V

1 =

P2V

2

P1

= in

itia

l pre

ssu

reP

2=

fin

al p

ress

ure

V1

= in

itia

l vo

lum

eV

2=

fin

al v

olu

me

Page 6: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

The

pres

sure

insi

de a

tire

pum

p is

1.4

atm

at 3

.0 L

. If t

he v

olum

e is

de

crea

sed

to 2

.0 L

, wha

t is

the

new

air

pres

sure

? A

bubb

le o

f nat

ural

gas

(CH

4) h

as a

vol

ume

of 4

5.0

mL

at 1

.60

atm

of

pres

sure

whe

n un

derg

roun

d. W

hat v

olum

e w

ill th

e bu

bble

hav

e it

if re

ache

s Ea

rth’s

sur

face

whe

re a

tmos

pher

ic p

ress

ure

is 7

44 m

mH

g? A

ssum

e no

ch

ange

in te

mpe

ratu

re o

r am

ount

of g

as. (

760

mm

Hg

= 1

atm

)

FY

I –P

V r

elat

ion

ship

in B

reat

hin

g

Th

e im

port

ance

of B

oyl

e’s

Law

is

sho

wn

in t

he

mec

han

ics

of

bre

ath

ing.

Ou

r lu

ngs

are

ela

stic

, bal

loo

n-l

ike

stru

ctu

res

con

tain

ed in

an

air

tigh

t ch

amb

er c

alle

d t

he

tho

raci

c ca

vity

. T

he

dia

phra

gm, a

mu

scle

, fo

rms

the

flex

ible

flo

or

of t

he

cavi

ty.

FY

I –P

V r

elat

ion

ship

in B

reat

hin

g

IInha

lati

on (I

nspi

rati

on)

Th

e p

roce

ss o

f tak

ing

a b

reat

h b

egin

s w

hen

th

e d

iaph

ragm

co

ntr

acts

, cau

sin

g an

incr

ease

in t

he

volu

me

of t

he

lun

gs. A

cco

rdin

g to

Bo

yle’

s La

w,

this

cau

ses

pres

sure

in t

he

lun

gs t

o d

ecre

ase.

Th

e pr

essu

re o

f th

e lu

ngs

dro

p b

elo

w t

he

atm

osp

her

ic p

ress

ure

cre

atin

g a

pre

ssu

re

grad

ien

t b

etw

een

th

e lu

ngs

an

d a

tmo

sph

ere.

Air

mo

lecu

les

flo

w fr

om

hig

her

pre

ssu

re t

o

low

er a

nd

yo

u b

reat

he

in.

Page 7: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

FY

I –P

V r

elat

ion

ship

in B

reat

hin

g

EExh

alat

ion

(Exp

irat

ion)

occ

urs

wh

en t

he

dia

phra

gm r

elax

es a

nd

mo

ves

bac

k u

p in

to t

he

tho

raci

c ca

vity

. Th

e vo

lum

e o

f th

e th

ora

cic

cavi

ty a

nd

lun

gs d

ecre

ase,

cau

sin

g an

incr

ease

in

th

e p

ress

ure

in t

he

lun

gs.

No

w t

he

pre

ssu

re in

th

e lu

ngs

in h

igh

er t

han

th

e pr

essu

re o

f th

e at

mo

sph

ere

and

a n

ew

pre

ssu

re g

rad

ien

t ca

use

s th

e ai

r m

ole

cule

s to

fl

ow

ou

t o

f th

e lu

ngs

.

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Lo

w8

.6 –

Vo

lum

e an

d M

ole

s (A

voga

dro’

s La

w)

8.7

–T

he

Idea

l Gas

Law

8.8

–P

arti

al P

ress

ures

(Dal

ton’

s La

w)

8.3

Tem

per

atu

re a

nd

Vo

lum

e (C

har

les’

Law

)G

oal

: Use

th

e te

mp

erat

ure

-vo

lum

e re

lati

ons

hip

(Ch

arle

s’

Law

) to

det

erm

ine

the

fin

al t

emp

erat

ure

or

volu

me

wh

en

the

pres

sure

an

d a

mo

un

t o

f gas

are

co

nst

ant.

Ho

t ai

r b

allo

on

s…

Yo

u a

re g

oin

g to

tak

e a

rid

e in

a h

ot

air

bal

loo

n.

Th

e ca

ptai

n t

urn

s o

n a

pro

pan

e b

urn

er t

o h

eat

the

air

insi

de

the

bal

loo

n. A

s th

e ai

r is

hea

ted

, it

exp

and

s an

d b

eco

mes

less

den

se th

an t

he

air

ou

tsid

e, c

ausi

ng

the

bal

loo

n t

o r

ise…

Page 8: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Ch

arle

s’ L

aw

In 1

78

7, J

acq

ues

Ch

arle

s, a

bal

loo

nis

t an

d p

hys

icis

t,

pro

po

sed

that

th

e vo

lum

e o

f a g

as is

dir

ectl

y re

late

dto

te

mp

erat

ure

.

CCh

arle

s’ L

aw:

Th

e vo

lum

e (V

) of a

gas

is d

irec

tly

rela

ted

to

th

e te

mp

erat

ure

(T) w

hen

th

ere

is n

o

chan

ge in

th

e pr

essu

re (P

) or

amo

un

t (n

) of g

as.

29

Ch

arle

s’ L

aw

=co

nst

ant P

an

d n

*Use

Kel

vins

to a

void

neg

ativ

e nu

mbe

rs.

30

A sa

mpl

e of

hel

ium

gas

has

a v

olum

e of

5.4

0 L

and

a te

mpe

ratu

re o

f 15°

C.

Wha

t is

the

final

vol

ume,

in li

ters

, of t

he g

as if

the

tem

pera

ture

has

bee

n in

crea

sed

to 4

2°C

at c

onst

ant p

ress

ure

and

amou

nt o

f gas

.C

hap

ter

888

.1 -

Pro

pert

ies

of G

ases

8.2

–P

ress

ure

and

Vo

lum

e (B

oyle

’s L

aw)

8.3

–T

empe

ratu

re a

nd

Vo

lum

e (C

harl

es’ L

aw)

8.4

–T

empe

ratu

re a

nd

Pre

ssur

e (G

uy-L

ussa

c’s

Law

)8

.5 –

Th

e C

om

bine

d G

as L

ow

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

Page 9: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

8.4

Tem

per

atu

re a

nd

Pre

ssu

re

(Gay

-Lu

ssac

’s L

aw)

Go

al:

Use

th

e te

mp

erat

ure

-pre

ssu

re r

elat

ion

ship

(Gay

-Lu

ssac

’s L

aw) t

o d

eter

min

e th

e fi

nal

tem

per

atu

re o

r pr

essu

re

wh

en t

he

volu

me

and

am

ou

nt

of g

as a

re c

on

stan

t.

If w

e co

uld

ob

serv

e th

e m

ole

cule

s o

f a g

as a

s th

e te

mpe

ratu

re r

ises

, we

wo

uld

no

tice

th

at t

hey

mo

ve

fast

er a

nd

hit

th

e si

des

of t

he

con

tain

er m

ore

oft

en

and

wit

h g

reat

er fo

rce.

If v

olu

me

and

th

e am

ou

nt o

f gas

are

kep

t th

e sa

me,

w

e w

ou

ld s

ee a

n in

crea

se o

f pre

ssu

re.

34

Gay

-Lu

ssac

’s L

awGG

ay-L

ussa

c’s

Law

: th

e p

ress

ure

of a

gas

is d

irec

tly

rela

ted

to it

s K

elvi

n t

empe

ratu

re a

t a

con

stan

t vo

lum

e an

d a

mo

un

t of g

as =co

nst

ant n

an

d V

*All

tem

pera

ture

s in

Kel

vin

35

An o

xyge

n ta

nk h

as a

pre

ssur

e of

120

atm

at ro

om te

mpe

ratu

re o

f 25.

0°C

. If

a fir

e in

the

room

cau

ses

the

tem

pera

ture

of t

he g

as in

the

tank

to re

ach

402°

C, w

hat w

ill be

its

pres

sure

?

Tank

s ca

n ru

ptur

e if

pres

sure

exc

eeds

180

atm

. Will

it ex

plod

e?

Page 10: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Vap

or

Pre

ssu

re

Wh

en li

qu

id m

ole

cule

s ga

in s

uff

icie

nt

kin

etic

en

ergy

, th

ey b

reak

way

fro

m t

he

surf

ace

and

b

eco

me

gas

part

icle

s o

r va

por.

In a

n o

pen

co

nta

iner

, all

the

liqu

id w

ill

even

tual

ly e

vapo

rate

.

In a

clo

se c

on

tain

er, t

he

vapo

r ac

cum

ula

tes

abo

ve t

he

liqu

id a

nd

cre

ates

pre

ssu

re c

alle

d

vvapo

r pre

ssur

e.

37

Vap

or

Pre

ssu

reE

ach

typ

e o

f liq

uid

exe

rts

its

ow

n v

apo

r pr

essu

re a

t a

give

n t

empe

ratu

re.

As

the

tem

pera

ture

incr

ease

s, m

ore

vap

or

form

s, a

nd

th

e va

por

pre

ssu

re in

crea

ses.

Bo

ilin

g p

oin

tA

liq

uid

rea

ches

its

bbo

iling

po

int w

hen

its

vapo

r p

ress

ure

bec

om

es e

qu

al t

o t

he

exte

rnal

(atm

osp

her

ic)

pres

sure

.

At

hig

h a

ltit

ud

es, w

her

e at

mo

sph

eric

pre

ssu

re is

lo

wer

, th

e va

por

pre

ssu

re to

rea

ch is

low

er, s

o w

ater

b

oils

at

a lo

wer

tem

pera

ture

!

Atm

osph

eric

pr

essu

reB

oilin

g po

int

of w

ater

Sea

Leve

l76

0 m

mH

g10

0°C

Den

ver

630

mm

Hg

95°C

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Law

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

Page 11: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

8.5

Th

e C

om

bin

ed G

as L

awG

oal

: U

se t

he

com

bin

ed g

as la

w t

o c

alcu

late

th

e fi

nal

V, P

, or

T o

f a g

as w

hen

ch

ange

s in

2 o

f th

ese

pro

pert

ies

are

give

n

and

the

amo

un

t o

f gas

is c

on

stan

t.

Co

mb

ined

Gas

Law

All

of t

he

Pre

ssu

re-V

olu

me-

Tem

pera

ture

rel

atio

nsh

ip

for

gase

s th

at w

e h

ave

stu

die

d m

ay b

e co

mb

ined

into

a

sin

gle

rela

tio

nsh

ip c

alle

d t

he

C Co

mbi

ned

Gas

Law

:

=co

nst

ant n

Co

mb

ined

Gas

Law

By

usi

ng

the

com

bin

ed g

as la

w, w

e ca

n d

eriv

e an

y o

f th

e ga

s la

ws

by

emit

tin

g th

e pr

ope

rtie

s th

at d

on

’t

chan

ge.

=co

nst

ant n

A 25

mL

bubb

le is

rele

ased

from

a d

iver

’s a

ir ta

nk a

t a p

ress

ure

of 4

.00

atm

and

a te

mpe

ratu

re o

f 11°

C. W

hat i

s th

e vo

lum

e, in

mL,

of t

he b

allo

on w

hen

it re

ache

s th

e oc

ean

surfa

ce w

here

the

pres

sure

is 1

.00

atm

and

the

tem

pera

ture

is 1

8°C

? (A

ssum

e th

e am

ount

of g

as in

the

bubb

le d

oes

not c

hang

e.)

Page 12: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Law

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

8.6

Vo

lum

e an

d M

ole

s (A

voga

dro

’s L

aw)

Go

al:

Use

Avo

gad

ro’s

Law

to

cal

cula

te t

he

amo

un

t o

f vo

lum

e of

a g

as w

hen

the

pre

ssur

e an

d t

emp

erat

ure

are

con

stan

t.

Up

tiln

ow

, we

hav

e al

way

s ke

pt t

he

amo

un

t of g

as (n

) co

nst

ant.

No

w w

e w

ill c

on

sid

er th

e af

fect

s w

hen

gr

ams

or

mo

les

chan

ge.

Wh

en y

ou

blo

w u

p a

bal

loo

n, i

ts v

olu

me

incr

ease

s b

ecau

se

you

ad

d m

ore

air

mo

lecu

les.

If t

he

bal

loo

n h

as a

ho

le in

it, a

ir le

aks

ou

t, c

ausi

ng

its

volu

me

to d

ecre

ase.

se

W

Page 13: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Avo

gad

ro’s

Law

In 1

81

1, A

med

eoA

voga

dro

pro

pose

d:

AAvo

gadr

o’s

Law

: Th

e vo

lum

e o

f a g

as is

dir

ectl

y re

late

d t

o t

he

nu

mb

er o

f mo

les

of a

gas

wh

en T

an

d P

d

o n

ot

chan

ge.

Fo

r ex

amp

le, i

f th

e n

um

ber

of m

ole

s o

f gas

do

ub

les,

th

en t

he

volu

me

will

do

ub

le t

oo

, as

lon

g as

P a

nd

T d

o

no

t ch

ange

.

=co

nst

ant

P a

nd

T

A w

eath

er b

allo

on w

ith a

vol

ume

of 4

4 L

is fi

lled

with

2.0

mol

es o

f He.

Wha

t is

the

final

vol

ume

if 3.

0 m

oles

are

add

ed fo

r a to

tal o

f 5.0

mol

es?

(P a

nd T

don

’t ch

ange

.)

Usi

ng

Avo

gad

ro’s

Law

, we

can

say

an

y tw

o g

ases

will

h

ave

equ

al v

olu

mes

if t

hey

co

nta

in t

he

sam

e n

um

ber

o

f mo

les

of g

as (a

t th

e sa

me

T a

nd

P).

STP

Stan

dar

d T

emp

erat

ure

an

d P

ress

ure

“ST

P” i

s a

han

dy

abb

revi

atio

n fo

r 3

73

K (O

°C) a

nd

1 a

tm. A

co

mm

on

set

o

f un

its.

At

STP

, on

e m

ole

of a

ny

gas

occ

up

ies

a vo

lum

e o

f 22

.4 L

(r

ou

ghly

th

e vo

lum

e o

f th

e 3

bas

ketb

alls

).

Page 14: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Mo

lar

Vo

lum

eT

he

volu

me,

22

.4 L

, of a

ny

gas

at S

TP

is c

alle

d it

s mm

ola

r vo

lum

e.

Wh

en a

gas

is a

t ST

P c

on

dit

ion

s (O

C a

nd

1 a

tm),

its

mo

lar

volu

me

can

be

use

d a

s a

con

vers

ion

fact

or

bet

wee

n #

of m

ole

s an

d v

olu

me:

1 22.4

Wha

t is

the

volu

me,

in li

ters

, in

64.0

g o

f O2

gas

at S

TP?

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Law

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

8.7

Th

e Id

eal G

as L

awG

oal

: U

se t

he

idea

l gas

law

eq

uat

ion

to

so

lve

for

P, V

, T, o

r n

of a

ga

s w

hen

giv

en 3

of t

he

4 v

alu

es in

th

e id

eal g

as la

w e

qu

atio

n.

Cal

cula

te t

he

mas

s o

r vo

lum

e o

f a g

as in

a c

hem

ical

rea

ctio

n.

Page 15: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Idea

l Gas

Law

Th

eiid

eal g

as la

wis

th

e co

mb

inat

ion

of t

he

4

pro

per

ties

use

d to

mea

sure

gas

es -

P, V

, T, n

–to

giv

e a

sin

gle

equ

atio

n:

=

Idea

l Gas

Co

nst

ant

=

N2O

is a

n an

esth

etic

(lau

ghin

g ga

s).

Wha

t is

the

pres

sure

, in

atm

, of 0

.350

mol

e of

N2O

at 2

2°C

in a

5.0

0 L

cont

aine

r?

Page 16: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Oft

en w

e n

eed

to

kn

ow

th

e am

ou

nt o

f gas

(in

gra

ms)

in

volv

ed in

a r

eact

ion

.

Th

en t

he

Idea

l Gas

Law

can

be

rear

ran

ged

to

so

lve

for

mo

les

(n) t

hen

co

nve

rt t

o g

ram

s u

sin

g m

ola

r m

ass.

61

Buta

ne, C

4H10

, is

used

as

a fu

el fo

r cam

p st

oves

. If

you

have

108

mL

of b

utan

e ga

s at

715

mm

Hg

and

25°C

, wha

t is

the

mas

s, in

gr

ams,

of b

utan

e.

Gas

Law

s an

d

Ch

emic

al R

eact

ion

sG

ases

are

invo

lved

as

reac

tan

ts a

nd

pro

du

cts

in m

any

chem

ical

rea

ctio

ns.

Typ

ical

ly t

he

info

rmat

ion

giv

en

for

a ga

s is

its

P, V

, an

d T

. Th

en w

e ca

n u

se t

he

idea

l ga

s la

w t

o d

eter

min

e th

e m

ole

s o

f a g

as in

a r

eact

ion

.

If w

e kn

ow

th

e n

um

ber

of m

ole

s fo

r o

ne

of t

he

gase

s,

we

can

use

mo

le-m

ole

fact

ors

to

det

erm

ine

the

mo

les

of a

ny

oth

er s

ub

stan

ce.

63

Cal

cium

car

bona

te (C

aCO

3) in

ant

acid

s re

acts

with

HC

lin

the

stom

ach

to re

duce

ac

id re

flux.

How

man

y L

of C

O2

are

prod

uced

at 7

52 m

mH

g an

d 24

°C fr

om a

25.

0 g

sam

ple

of c

alci

um c

arbo

nate

.

CaC

O3(

s) +

2H

Cl(a

q)

CO

2(g)

+ H

2O(l)

+ C

aCl 2(

aq)

Page 17: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Law

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)

8.8

Par

tial

Pre

ssu

res

(Dal

ton

’s L

aw)

Go

al:

Use

Dal

ton

’s L

aw o

f par

tial

pre

ssu

res

to c

alcu

late

th

e to

tal

pres

sure

of a

mix

ture

of g

ases

.

Gas

Mix

ture

sM

any

gas

sam

ple

s ar

e a

mix

ture

of g

ases

.

Fo

r ex

ampl

e : t

he

air

we

bre

ath

e is

a m

ix o

f mai

nly

n

itro

gen

an

d o

xyge

n.

In g

as m

ixtu

res,

sci

enti

sts

ob

serv

ed t

hat

all

gas

part

icle

s b

ehav

e in

th

e sa

me

way

.

Th

eref

ore

th

e to

tal p

ress

ure

of t

he

gase

s in

a m

ixtu

re

is a

res

ult

of t

he

colli

sio

ns

of t

he

gas

par

ticl

es

rega

rdle

ss o

f wh

at t

ype

of g

as t

hey

are

.

67

Dal

ton

’s L

awIn

a g

as m

ixtu

re, e

ach

gas

exe

rts

its

ppar

tial

pre

ssur

e(t

he

pres

sure

it w

ou

ld e

xert

if it

wer

e th

e o

nly

gas

in

the

con

tain

er).

Dal

ton’

s La

w s

tate

s th

at t

he

tota

l pre

ssu

re o

f a g

as is

th

e su

m o

f th

e pa

rtia

l pre

ssu

res

of t

he

gase

s in

th

e m

ixtu

re.

Pto

tal=

P1

+ P

2+

P3

+ …

68

Page 18: Chapter 8 Gases - Chemistry Department - chem.usu.eduion.chem.usu.edu/~scheiner/LundellChemistry/lectureslides/ch08... · 8.2 Pressure and Volume (Boyle’s Law) Goal: Use the pressure-volume

Exa

mp

le

If w

e co

mb

ine

the

gase

s in

to o

ne

tan

k, w

ith

th

e sa

me

V a

nd

T, t

he

nu

mb

er o

f gas

mo

lecu

les

(n) d

eter

min

e th

e p

ress

ure

of t

he

tan

k.

It d

oes

no

t m

atte

r w

hat

typ

e o

f gas

(He

or

Ar)

. Sim

ply

h

ow

man

y at

om

s o

f gas

th

ere

are.

69

A he

liox

brea

thin

g m

ixtu

re o

f oxy

gen

and

heliu

m is

pre

pare

d fo

r a p

atie

nt. T

he g

as

mix

ture

has

a to

tal p

ress

ure

of 7

.00

atm

. If t

he p

artia

l pre

ssur

e of

the

oxyg

en is

114

m

mH

g, w

hat i

s th

e pa

rtial

pre

ssur

e of

the

heliu

m?

Ch

apte

r 8

88.1

-P

rope

rtie

s o

f Gas

es8

.2 –

Pre

ssur

e an

d V

olu

me

(Boy

le’s

Law

)8

.3 –

Tem

pera

ture

an

d V

olu

me

(Cha

rles

’ Law

)8

.4 –

Tem

pera

ture

an

d P

ress

ure

(Guy

-Lus

sac’

sLa

w)

8.5

–T

he

Co

mbi

ned

Gas

Law

8.6

–V

olu

me

and

Mo

les

(Avo

gadr

o’s

Law

)8

.7 –

Th

e Id

eal G

as L

aw8

.8 –

Par

tial

Pre

ssur

es (D

alto

n’s

Law

)