Review Session-3

Review Session-3 -...

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Unformatted text preview: 10.32)
Suppose
you
are
given
2
flasks
at
same
Temperature,
one
of

 volume
2L
and
the
other
of
volume
3L.
The
2L
flask
contains
4.8g
of
 gas
at
X
atm
pressure.
The
3L
flask
contains
0.36g
of
a
gas
at
0.1X
atm.
 Do
the
two
gases
contain
the
same
molar
mass?
If
not
which
gas
 contains
higher
molar
mass?
 10.32)
Suppose
you
are
given
2
flasks
at
same
Temperature,
one
of

 volume
2L
and
the
other
of
volume
3L.
The
2L
flask
contains
4.8g
of
 gas
at
X
atm
pressure.
The
3L
flask
contains
0.36g
of
a
gas
at
0.1X
atm.
 Do
the
two
gases
contain
the
same
molar
mass?
If
not
which
gas
 contains
higher
molar
mass?
 PV=nRT
 n=
PV/RT
 Wt/MWt=
PV/RT
 Mwt
=
Wt.
RT/PV

 10.32)
Suppose
you
are
given
2
flasks
at
same
Temperature,
one
of

 volume
2L
and
the
other
of
volume
3L.
The
2L
flask
contains
4.8g
of
 gas
at
X
atm
pressure.
The
3L
flask
contains
0.36g
of
a
gas
at
0.1X
atm.
 Do
the
two
gases
contain
the
same
molar
mass?
If
not
which
gas
 contains
higher
molar
mass?
 PV=nRT
 2L
Flask:
Mwt
=
(4.8)
RT/2X
=
(2.4)
RT/X

 n=
PV/RT
 3L
Flask:
Mwt
=
(0.36)
RT/3
(0.1X)
=
(1.2)
RT/X

 Wt/MWt=
PV/RT
 The
Molar
mass
of
the
gas
in
2L
flask
is
twice
 as
large
as
the
molar
mass
of
the
gas
in
3L
flask
 Mwt
=
Wt.
RT/PV

 10.59)
 N2
 O2
 2L
 1.0
atm
 25oC
 3L
 2.0
atm
 25oC
 (a)
When
the
stopcock
between
the
two
containers
is
opened
and
 gases
allowed
to
mix,
how
does
the
volume
occupied
by
N2
gas
 changes?
What
is
the
parXal
P
of
N2
gas
aYer
mixing?
 10.59)
 N2
 O2
 2L
 1.0
atm
 25oC
 3L
 2.0
atm
 25oC
 (a)
When
the
stopcock
between
the
two
containers
is
opened
and
 gases
allowed
to
mix,
how
does
the
volume
occupied
by
N2
gas
 changes?
What
is
the
parXal
P
of
N2
gas
aYer
mixing?
 Volume
occupied
by
N2
will
change
from
2L
to
5L

(2L+3L)
 At
Constant
T,
P1V1=
P2V2
 1atm
X
2L
=
P2X
5L


P2
=
0.4
atm
 10.59)
 N2
 O2
 2L
 1.0
atm
 25oC
 3L
 2.0
atm
 25oC
 (b)
How
does
the
volume
occupied
by
O2
gas
change
when
gases
 mix?
What
is
the
parXal
P
of
O2
gas
aYer
mixing?
 10.59)
 N2
 O2
 2L
 1.0
atm
 25oC
 3L
 2.0
atm
 25oC
 (b)
How
does
the
volume
occupied
by
O2
gas
change
when
gases
 mix?
What
is
the
parXal
P
of
O2
gas
aYer
mixing?
 Volume
occupied
by
O2
will
change
from
3L
to
5L

(2L+3L)
 At
Constant
T,
P1V1=
P2V2
 2atm
X
3L
=
P2X
5L


P2
=
1.2
atm
 10.59)
 N2
 O2
 2L
 1.0
atm
 25oC
 3L
 2.0
atm
 25oC
 (c)
What
is
the
total
P
of
the
container
aYer
the
gases
mix?
 PT
=
PN2
+
PO2
=
0.4+1.2
=
1.6
atm
 10.81)
Arsenic
(III)
sulfide
sublimes
readily,
even
below
its
melXng
 point
of
320oC.
The
molecules
of
the
vapor
phase
are
found
to
effuse
 through
a
Xny
hole
at
0.28
Xmes
the
rate
of
effusion
of
Argon
atoms
 under
the
same
condiXons
of
T
and
P.
What
is
the
molecular
formula
of
 As(III)
sulfide
in
the
gas
phase?
 10.81)
Arsenic
(III)
sulfide
sublimes
readily,
even
below
its
melXng
 point
of
320oC.
The
molecules
of
the
vapor
phase
are
found
to
effuse
 through
a
Xny
hole
at
0.28
Xmes
the
rate
of
effusion
of
Argon
atoms
 under
the
same
condiXons
of
T
and
P.
What
is
the
molecular
formula
of
 As(III)
sulfide
in
the
gas
phase?
 r(AS)/r(Ar)
=0.28
=
(MAr/
MAS)
½
 MAs
=
(39.9/0.28)2
=
510g/mol


 Typical
formula
of
As(III)sulfide:

As2S3
=
246.1g/mol
 So
it
exists
as
dimer
in
vapor
state:
As4S6
 11.63)
An
element
crystallizes
in
a
BCC
ladce.
The
edge
of
the
unit
cell
 is
2.86Ao
and
the
density
of
the
crystal
is
7.92g/cm3.
Calculate
the
 atomic
weight
of
the
element.
 11.63)
An
element
crystallizes
in
a
BCC
ladce.
The
edge
of
the
unit
cell
 is
2.86Ao
and
the
density
of
the
crystal
is
7.92g/cm3.
Calculate
the
 atomic
weight
of
the
element.
 BCC


1(Center)
+
8
(1/8)
(corners)
=
1+1
=
2
atoms
 Mass
of
unit
cell:

(m)=
Volume
X
density
 m=
(2.86Ao)3
(7.92g/cm3)
(10‐8
cm)3
 m
=
1.85X10‐22g/unit
cell
 2
atoms
present
in
unit
cell
 (1.85X10‐22g/2)
X6.02X1023atoms/mol
 =
55.8g/mol
 It
could
be
Iron!
(Fe:
55.85g/mol)
 11.67)
Clausthalite
is
a
mineral
composed
of
lead
Selenide
(PbSe).
The
 mineral
adopts
a
NaCl
type
structure.
The
density
of
PbSe
is
8.27g/cm3.

 Calculate
the
length
of
an
edge
of
the
PbSe
unit
cell?

 11.67)
Clausthalite
is
a
mineral
composed
of
lead
Selenide
(PbSe).
The
 mineral
adopts
a
NaCl
type
structure.
The
density
of
PbSe
is
8.27g/cm3.

 Calculate
the
length
of
an
edge
of
the
PbSe
unit
cell?

 NaCl
type:
means
4
Pb
and
4
Selenium
present
in
the
unit
cell
 4(207.2)
+
4(78.96)
=
1144.6
amu
 d=
m/V


V=
m/d
‐
a3=
m/d
 8.27g/cm3

=
1144.6amu
(1g)
/(axaxa)
(6.02X1023)(amu)
 a3=
22.99X10‐23cm3
=
223X10‐24
 a=
6.12
X
10‐8
cm
=
6.12Ao
 11.67)
Iridium
crystalizes
in
FCC
that
has
an
edge
length
of
3.833Ao.
 Calculate
the
atomic
radius
of
Iridium
(b)
calculate
the
Density
?
 11.67)
Iridium
crystalizes
in
FCC
that
has
an
edge
length
of
3.833Ao.
 Calculate
the
atomic
radius
of
Iridium
(b)
calculate
the
Density
?
 Length
of
the
face
diagonal:
 a
 a
 (a2+a2)
½
=

√2.
a
 11.67)
Iridium
crystalizes
in
FCC
that
has
an
edge
length
of
3.833Ao.
 Calculate
the
atomic
radius
of
Iridium
(b)
calculate
the
Density
?
 Length
of
the
face
diagonal
=
4
(radius
of
atom)
 √2.
a
=
4r
 r=
√2.(3.833)/4
=1.355Ao
 r
 2r
 r
 11.67)
Iridium
crystalizes
in
FCC
that
has
an
edge
length
of
3.833Ao.
 Calculate
the
atomic
radius
of
Iridium
(b)
calculate
the
Density
?
 Length
of
the
face
diagonal
=
4
(radius
of
atom)
 √2.
a
=
4r
 r=
√2.(3.833)/4
=1.355Ao
 r
 Mass=

4
Ir
atoms
=4(192.22)amu
 Volume
=
(1.355X10‐8cm)3
 d=
4(192.22)/(1.355X10‐8)(6.02X1023)
 D=
22.67g/cm3
 2r
 r
 Which
one
has
the
highest
total
molecular
volume
relaXve
to
the
space

 occupied
by
the
gas?
Ne,
N2,
SF6,
CH4
 Which
one
has
the
highest
total
molecular
volume
relaXve
to
the
space

 occupied
by
the
gas?
Ne,
N2,
SF6,
CH4
 Neon
:
Noble
gas,
Unimolecular
gas
 N2:
Diatomic
Gas
 SF6:
Sulfur
akached
to
6
fluorines.

 CH4:
Carbon
akached
to
4
Hydrogens
 SF6>
CH4>
N2>
Ne
 Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These Compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate to freeze 100 g of water initially at 18oC? (a) The heat required to reduce the water to 0oC is (b) The heat required to freeze the water at 0oC is (c) The required CFC mass is 21
 Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These Compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate to freeze 100 g of water initially at 18oC? (a) The heat required to reduce the water to 0oC is (100 g)( 4.18 J )(18 K ) = 7.5 kJ g−K q=
msΔT
 (b) The heat required to freeze the water at 0oC is € (c) The required CFC mass is 22
 Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These Compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate to freeze 100 g of water initially at 18oC? (a) The heat required to reduce the water to 0oC is (100 g)( 4.18 J )(18 K ) = 7.5 kJ g−K q=
msΔT
 (b) The heat required to freeze the water at 0oC is J (100 g)( 334 ) = 33.4 kJ g € q=mΔHfus
 (c) The required CFC mass is € 23
 Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These Compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate to freeze 100 g of water initially at 18oC? (a) The heat required to reduce the water to 0oC is (100 g)( 4.18 J )(18 K ) = 7.5 kJ g−K q=
msΔT
 (b) The heat required to freeze the water at 0oC is J (100 g)( 334 ) = 33.4 kJ g € q=mΔHfus
 (c) The required CFC mass is € ( 33.4 + 7.5) kJ = 142 g kJ 0.289 g mCFC=
Q/ΔHvap
 24
 ...
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