Page 1
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Physical
Chemistry
TOPIC: GASEOUS STATE CHEMISTRY
IIT-JAM/DU M.Sc./CSIR-NET/GATE
ALL FACULTY FROM IIT
2637, Hudson Lane, Behind Khalsa College, Near
G.T.B. Nagar Metro Station Gate No. 3 & 4, New
Delhi – 110009
Mob. 09555785548, 08860929430, e-mail:
info@asfinstitute.com, www.asfinstitute.com
Page 2
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Physical
Chemistry
TOPIC: GASEOUS STATE CHEMISTRY
IIT-JAM/DU M.Sc./CSIR-NET/GATE
ALL FACULTY FROM IIT
2637, Hudson Lane, Behind Khalsa College, Near
G.T.B. Nagar Metro Station Gate No. 3 & 4, New
Delhi – 110009
Mob. 09555785548, 08860929430, e-mail:
info@asfinstitute.com, www.asfinstitute.com
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
GASEOUS STATE
The state of matter in which the molecular forces of attraction between the particles of matter are
minimum, is known as gaseous state. It is the simplest state and shows great uniformity in behaviour.
Characteristics of gases.
(A) Gases or their mixtures are homogeneous in composition.
(B) Gases have very low density due to negligible intermolecular forces.
(C) Gases have infinite expansibility and high compressibility.
(D) Gases exert pressure.
(E) Gases possess high diffusibility.
(F) Gases do not have definite shape and volume like liquids.
(G) Gaseous molecules move very rapidly in all directions in a random manner i.e., gases have highest kinetic
energy.
(H) Gaseous molecules are loosely packed having large empty spaces between them.
(I) Gaseous molecules collide with one another and also with the walls of container with perfectly elastic
collisions.
(J) Gases can be liquified, if subjected to low temperatures (below critical) or high pressures.
(K) Thermal energy of gases >> molecular attraction.
(L) Gases undergo similar change with the change of temperature and pressure. In other words, gases obey
certain laws known as gas laws.
Measurable properties of gases.
(A) The characteristics of gases are described fully in terms of four parameters or measurable properties :
(i) The volume, V, of the gas.
(ii) Its pressure, P
(iii)Its temperature, T
(iv) The amount of the gas (i.e., mass or number of moles).
(B) Volume : (a)Since gases occupy the entire space available to them, the measurement of volume of a
gas only requires a measurement of the container confining the gas.
(b) Volume is expressed in litres (L), millilitres (mL) or cubic centimetres ) (
3
cm or cubic metres ) (
3
m .
(c) mL L 1000 1 ? ; L mL
3
10 1
?
?
3 3 3
10 1 1 cm dm L ? ?
L mL cm dm m
3 6 3 6 3 3 3
10 10 10 10 1 ? ? ? ?
(C) Mass : (a) The mass of a gas can be determined by weighing the container in which the gas is enclosed
and again weighing the container after removing the gas. The difference between the two weights gives the
mass of the gas.
(b) The mass of the gas is related to the number of moles of the gas i.e.
Page 3
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Physical
Chemistry
TOPIC: GASEOUS STATE CHEMISTRY
IIT-JAM/DU M.Sc./CSIR-NET/GATE
ALL FACULTY FROM IIT
2637, Hudson Lane, Behind Khalsa College, Near
G.T.B. Nagar Metro Station Gate No. 3 & 4, New
Delhi – 110009
Mob. 09555785548, 08860929430, e-mail:
info@asfinstitute.com, www.asfinstitute.com
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
GASEOUS STATE
The state of matter in which the molecular forces of attraction between the particles of matter are
minimum, is known as gaseous state. It is the simplest state and shows great uniformity in behaviour.
Characteristics of gases.
(A) Gases or their mixtures are homogeneous in composition.
(B) Gases have very low density due to negligible intermolecular forces.
(C) Gases have infinite expansibility and high compressibility.
(D) Gases exert pressure.
(E) Gases possess high diffusibility.
(F) Gases do not have definite shape and volume like liquids.
(G) Gaseous molecules move very rapidly in all directions in a random manner i.e., gases have highest kinetic
energy.
(H) Gaseous molecules are loosely packed having large empty spaces between them.
(I) Gaseous molecules collide with one another and also with the walls of container with perfectly elastic
collisions.
(J) Gases can be liquified, if subjected to low temperatures (below critical) or high pressures.
(K) Thermal energy of gases >> molecular attraction.
(L) Gases undergo similar change with the change of temperature and pressure. In other words, gases obey
certain laws known as gas laws.
Measurable properties of gases.
(A) The characteristics of gases are described fully in terms of four parameters or measurable properties :
(i) The volume, V, of the gas.
(ii) Its pressure, P
(iii)Its temperature, T
(iv) The amount of the gas (i.e., mass or number of moles).
(B) Volume : (a)Since gases occupy the entire space available to them, the measurement of volume of a
gas only requires a measurement of the container confining the gas.
(b) Volume is expressed in litres (L), millilitres (mL) or cubic centimetres ) (
3
cm or cubic metres ) (
3
m .
(c) mL L 1000 1 ? ; L mL
3
10 1
?
?
3 3 3
10 1 1 cm dm L ? ?
L mL cm dm m
3 6 3 6 3 3 3
10 10 10 10 1 ? ? ? ?
(C) Mass : (a) The mass of a gas can be determined by weighing the container in which the gas is enclosed
and again weighing the container after removing the gas. The difference between the two weights gives the
mass of the gas.
(b) The mass of the gas is related to the number of moles of the gas i.e.
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
moles of gas (n)
M
m
? ?
mass Molar
grams in Mass
(iii)Mass is expressed in grams or kilograms, g Kg
3
10 1 ?
(D) Temperature : (a) Gases expand on increasing the temperature. If temperature is increased twice, the
square of the velocity ) (
2
v also increases two times.
(b) Temperature is measured in centigrade degree ) ( C
o
or celsius degree with the help of
thermometers. Temperature is also measured in Fahrenheit (F
o
).
(c) S.I. unit of temperature is kelvin (K) or absolute degree.
273 ? ? C K
o
(iv) Relation between F and C
o
is
9
32
5
?
?
o o
F C
(E) Pressure : (a) Pressure of the gas is the force exerted by the gas per unit area of the walls of the
container in all directions. Thus, Pressure (P)
) ( Area
) ( on Accelerati ) ( Mass
) Area(
) Force(
a
a m
A
F ?
? ?
(b) Pressure exerted by a gas is due to kinetic energy )
2
1
(
2
mv KE ? of the molecules. Kinetic energy of
the gas molecules increases, as the temperature is increased. Thus, Pressure of a gas ? Temperature (T).
(c) Pressure of a pure gas is measured by manometer while that of a mixture of gases by barometer.
(d) Commonly two types of manometers are used,
(a) Open end manometer; (b) Closed end manometer
(e) The S.I. unit of pressure, the pascal (Pa), is defined as 1 newton per metre square. It is very small
unit.
2 1 2
1 1 1
? ? ?
? ? s m kg Nm Pa
(f) C.G.S. unit of pressure is dynes
2 ?
cm .
(g) M.K.S. unit of pressure is
2
/ m kgf . The unit
2
/ cm kgf sometime called ata (atmosphere technical
absolute).
(h) Higher unit of pressure is bar, KPa or MPa.
KPa KNm Nm Pa bar 100 100 10 10 1
2 2 5 5
? ? ? ?
? ?
(i) Several other units used for pressure are,
Name Symbol Value
bar bar Pa bar
5
10 1 ?
atmosphere atm Pa atm
5
10 01325 . 1 1 ? ?
Torr Torr
Pa Pa Torr 322 . 133
760
101325
1 ? ?
millimetre of mercury mm Hg
Pa Hg mm 322 . 133 1 ?
(j) The pressure relative to the atmosphere is called gauge pressure. The pressure relative to the
perfect vacuum is called absolute pressure.
Page 4
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Physical
Chemistry
TOPIC: GASEOUS STATE CHEMISTRY
IIT-JAM/DU M.Sc./CSIR-NET/GATE
ALL FACULTY FROM IIT
2637, Hudson Lane, Behind Khalsa College, Near
G.T.B. Nagar Metro Station Gate No. 3 & 4, New
Delhi – 110009
Mob. 09555785548, 08860929430, e-mail:
info@asfinstitute.com, www.asfinstitute.com
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
GASEOUS STATE
The state of matter in which the molecular forces of attraction between the particles of matter are
minimum, is known as gaseous state. It is the simplest state and shows great uniformity in behaviour.
Characteristics of gases.
(A) Gases or their mixtures are homogeneous in composition.
(B) Gases have very low density due to negligible intermolecular forces.
(C) Gases have infinite expansibility and high compressibility.
(D) Gases exert pressure.
(E) Gases possess high diffusibility.
(F) Gases do not have definite shape and volume like liquids.
(G) Gaseous molecules move very rapidly in all directions in a random manner i.e., gases have highest kinetic
energy.
(H) Gaseous molecules are loosely packed having large empty spaces between them.
(I) Gaseous molecules collide with one another and also with the walls of container with perfectly elastic
collisions.
(J) Gases can be liquified, if subjected to low temperatures (below critical) or high pressures.
(K) Thermal energy of gases >> molecular attraction.
(L) Gases undergo similar change with the change of temperature and pressure. In other words, gases obey
certain laws known as gas laws.
Measurable properties of gases.
(A) The characteristics of gases are described fully in terms of four parameters or measurable properties :
(i) The volume, V, of the gas.
(ii) Its pressure, P
(iii)Its temperature, T
(iv) The amount of the gas (i.e., mass or number of moles).
(B) Volume : (a)Since gases occupy the entire space available to them, the measurement of volume of a
gas only requires a measurement of the container confining the gas.
(b) Volume is expressed in litres (L), millilitres (mL) or cubic centimetres ) (
3
cm or cubic metres ) (
3
m .
(c) mL L 1000 1 ? ; L mL
3
10 1
?
?
3 3 3
10 1 1 cm dm L ? ?
L mL cm dm m
3 6 3 6 3 3 3
10 10 10 10 1 ? ? ? ?
(C) Mass : (a) The mass of a gas can be determined by weighing the container in which the gas is enclosed
and again weighing the container after removing the gas. The difference between the two weights gives the
mass of the gas.
(b) The mass of the gas is related to the number of moles of the gas i.e.
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
moles of gas (n)
M
m
? ?
mass Molar
grams in Mass
(iii)Mass is expressed in grams or kilograms, g Kg
3
10 1 ?
(D) Temperature : (a) Gases expand on increasing the temperature. If temperature is increased twice, the
square of the velocity ) (
2
v also increases two times.
(b) Temperature is measured in centigrade degree ) ( C
o
or celsius degree with the help of
thermometers. Temperature is also measured in Fahrenheit (F
o
).
(c) S.I. unit of temperature is kelvin (K) or absolute degree.
273 ? ? C K
o
(iv) Relation between F and C
o
is
9
32
5
?
?
o o
F C
(E) Pressure : (a) Pressure of the gas is the force exerted by the gas per unit area of the walls of the
container in all directions. Thus, Pressure (P)
) ( Area
) ( on Accelerati ) ( Mass
) Area(
) Force(
a
a m
A
F ?
? ?
(b) Pressure exerted by a gas is due to kinetic energy )
2
1
(
2
mv KE ? of the molecules. Kinetic energy of
the gas molecules increases, as the temperature is increased. Thus, Pressure of a gas ? Temperature (T).
(c) Pressure of a pure gas is measured by manometer while that of a mixture of gases by barometer.
(d) Commonly two types of manometers are used,
(a) Open end manometer; (b) Closed end manometer
(e) The S.I. unit of pressure, the pascal (Pa), is defined as 1 newton per metre square. It is very small
unit.
2 1 2
1 1 1
? ? ?
? ? s m kg Nm Pa
(f) C.G.S. unit of pressure is dynes
2 ?
cm .
(g) M.K.S. unit of pressure is
2
/ m kgf . The unit
2
/ cm kgf sometime called ata (atmosphere technical
absolute).
(h) Higher unit of pressure is bar, KPa or MPa.
KPa KNm Nm Pa bar 100 100 10 10 1
2 2 5 5
? ? ? ?
? ?
(i) Several other units used for pressure are,
Name Symbol Value
bar bar Pa bar
5
10 1 ?
atmosphere atm Pa atm
5
10 01325 . 1 1 ? ?
Torr Torr
Pa Pa Torr 322 . 133
760
101325
1 ? ?
millimetre of mercury mm Hg
Pa Hg mm 322 . 133 1 ?
(j) The pressure relative to the atmosphere is called gauge pressure. The pressure relative to the
perfect vacuum is called absolute pressure.
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Absolute pressure = Gauge pressure + Atmosphere pressure.
(k) When the pressure in a system is less than atmospheric pressure, the gauge pressure becomes
negative, but is frequently designated and called vacuum. For example, 16 cm vacuum will be
bar 80 . 0 013 . 1
76
16 76
? ?
?
.
(l) If ‘h’ is the height of the fluid in a column or the difference in the heights of the fluid columns in
the two limbs of the manometer d the density of the fluid ) / 6 . 13 / 10 6 . 13 (
3 3 3
cm g m Kg Hg ? ? ? and g is the
gravity, then pressure is given by, dg h P P ? ?
atm gas
(m) Two sets of conditions are widely used as 'standard' values for reporting data.
Condition T P V
m
(Molar volume)
S.T.P./N.T.P. 273.15 K 1 atm 22.414 L
S.A.T.P
*
. 298.15 K 1 bar 24.800 L
* Standard Ambient temperature and pressure.
Boyle's law.
(A) In 1662, Robert Boyle discovered the first of several relationships among gas variables (P, T, V).
(B) It states that, “For a fixed amount of a gas at constant temperature, the gas volume is inversely
proportional to the gas pressure.”
Thus,
V
P
1
? at constant temperature and mass
or
V
K
P ? (where K is constant)
or K PV ?
For two or more gases at constant temperature and mass.
K V P V P ? ? ? .......
2 2 1 1
Boyle's law can also be given as,
2
v
K
dV
dP
T
? ? ?
?
?
?
?
?
Height (h) of
mercury column
Atmospheric
pressure
Vacuum
Mercury Barometer
h
?gas
?gas
?gas= ?gashdg
Hg
An open arm
manometer
Gas
Page 5
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Physical
Chemistry
TOPIC: GASEOUS STATE CHEMISTRY
IIT-JAM/DU M.Sc./CSIR-NET/GATE
ALL FACULTY FROM IIT
2637, Hudson Lane, Behind Khalsa College, Near
G.T.B. Nagar Metro Station Gate No. 3 & 4, New
Delhi – 110009
Mob. 09555785548, 08860929430, e-mail:
info@asfinstitute.com, www.asfinstitute.com
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
GASEOUS STATE
The state of matter in which the molecular forces of attraction between the particles of matter are
minimum, is known as gaseous state. It is the simplest state and shows great uniformity in behaviour.
Characteristics of gases.
(A) Gases or their mixtures are homogeneous in composition.
(B) Gases have very low density due to negligible intermolecular forces.
(C) Gases have infinite expansibility and high compressibility.
(D) Gases exert pressure.
(E) Gases possess high diffusibility.
(F) Gases do not have definite shape and volume like liquids.
(G) Gaseous molecules move very rapidly in all directions in a random manner i.e., gases have highest kinetic
energy.
(H) Gaseous molecules are loosely packed having large empty spaces between them.
(I) Gaseous molecules collide with one another and also with the walls of container with perfectly elastic
collisions.
(J) Gases can be liquified, if subjected to low temperatures (below critical) or high pressures.
(K) Thermal energy of gases >> molecular attraction.
(L) Gases undergo similar change with the change of temperature and pressure. In other words, gases obey
certain laws known as gas laws.
Measurable properties of gases.
(A) The characteristics of gases are described fully in terms of four parameters or measurable properties :
(i) The volume, V, of the gas.
(ii) Its pressure, P
(iii)Its temperature, T
(iv) The amount of the gas (i.e., mass or number of moles).
(B) Volume : (a)Since gases occupy the entire space available to them, the measurement of volume of a
gas only requires a measurement of the container confining the gas.
(b) Volume is expressed in litres (L), millilitres (mL) or cubic centimetres ) (
3
cm or cubic metres ) (
3
m .
(c) mL L 1000 1 ? ; L mL
3
10 1
?
?
3 3 3
10 1 1 cm dm L ? ?
L mL cm dm m
3 6 3 6 3 3 3
10 10 10 10 1 ? ? ? ?
(C) Mass : (a) The mass of a gas can be determined by weighing the container in which the gas is enclosed
and again weighing the container after removing the gas. The difference between the two weights gives the
mass of the gas.
(b) The mass of the gas is related to the number of moles of the gas i.e.
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
moles of gas (n)
M
m
? ?
mass Molar
grams in Mass
(iii)Mass is expressed in grams or kilograms, g Kg
3
10 1 ?
(D) Temperature : (a) Gases expand on increasing the temperature. If temperature is increased twice, the
square of the velocity ) (
2
v also increases two times.
(b) Temperature is measured in centigrade degree ) ( C
o
or celsius degree with the help of
thermometers. Temperature is also measured in Fahrenheit (F
o
).
(c) S.I. unit of temperature is kelvin (K) or absolute degree.
273 ? ? C K
o
(iv) Relation between F and C
o
is
9
32
5
?
?
o o
F C
(E) Pressure : (a) Pressure of the gas is the force exerted by the gas per unit area of the walls of the
container in all directions. Thus, Pressure (P)
) ( Area
) ( on Accelerati ) ( Mass
) Area(
) Force(
a
a m
A
F ?
? ?
(b) Pressure exerted by a gas is due to kinetic energy )
2
1
(
2
mv KE ? of the molecules. Kinetic energy of
the gas molecules increases, as the temperature is increased. Thus, Pressure of a gas ? Temperature (T).
(c) Pressure of a pure gas is measured by manometer while that of a mixture of gases by barometer.
(d) Commonly two types of manometers are used,
(a) Open end manometer; (b) Closed end manometer
(e) The S.I. unit of pressure, the pascal (Pa), is defined as 1 newton per metre square. It is very small
unit.
2 1 2
1 1 1
? ? ?
? ? s m kg Nm Pa
(f) C.G.S. unit of pressure is dynes
2 ?
cm .
(g) M.K.S. unit of pressure is
2
/ m kgf . The unit
2
/ cm kgf sometime called ata (atmosphere technical
absolute).
(h) Higher unit of pressure is bar, KPa or MPa.
KPa KNm Nm Pa bar 100 100 10 10 1
2 2 5 5
? ? ? ?
? ?
(i) Several other units used for pressure are,
Name Symbol Value
bar bar Pa bar
5
10 1 ?
atmosphere atm Pa atm
5
10 01325 . 1 1 ? ?
Torr Torr
Pa Pa Torr 322 . 133
760
101325
1 ? ?
millimetre of mercury mm Hg
Pa Hg mm 322 . 133 1 ?
(j) The pressure relative to the atmosphere is called gauge pressure. The pressure relative to the
perfect vacuum is called absolute pressure.
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
Absolute pressure = Gauge pressure + Atmosphere pressure.
(k) When the pressure in a system is less than atmospheric pressure, the gauge pressure becomes
negative, but is frequently designated and called vacuum. For example, 16 cm vacuum will be
bar 80 . 0 013 . 1
76
16 76
? ?
?
.
(l) If ‘h’ is the height of the fluid in a column or the difference in the heights of the fluid columns in
the two limbs of the manometer d the density of the fluid ) / 6 . 13 / 10 6 . 13 (
3 3 3
cm g m Kg Hg ? ? ? and g is the
gravity, then pressure is given by, dg h P P ? ?
atm gas
(m) Two sets of conditions are widely used as 'standard' values for reporting data.
Condition T P V
m
(Molar volume)
S.T.P./N.T.P. 273.15 K 1 atm 22.414 L
S.A.T.P
*
. 298.15 K 1 bar 24.800 L
* Standard Ambient temperature and pressure.
Boyle's law.
(A) In 1662, Robert Boyle discovered the first of several relationships among gas variables (P, T, V).
(B) It states that, “For a fixed amount of a gas at constant temperature, the gas volume is inversely
proportional to the gas pressure.”
Thus,
V
P
1
? at constant temperature and mass
or
V
K
P ? (where K is constant)
or K PV ?
For two or more gases at constant temperature and mass.
K V P V P ? ? ? .......
2 2 1 1
Boyle's law can also be given as,
2
v
K
dV
dP
T
? ? ?
?
?
?
?
?
Height (h) of
mercury column
Atmospheric
pressure
Vacuum
Mercury Barometer
h
?gas
?gas
?gas= ?gashdg
Hg
An open arm
manometer
Gas
2637, Hudson Lane, Behind Khalsa College, Near G.T.B. Nagar Metro Station Gate No. 3 & 4, New Delhi – 110009
Mob. 09555785548, 08860929430, e-mail: info@asfinstitute.com, www.asfinstitute.com
(C) Graphical representation of Boyle's law : Graph between P and V at constant temperature is called
isotherm and is an equilateral (or rectangular) hyperbola. By plotting P versus
V
1
, this hyperbola can be
converted to a straight line. Other types of isotherms are also shown below,
(D) At constant mass and temperature density of a gas is directly proportional to its pressure and inversely
proportional to its volume.
Thus,
V
P d
1
? ?
?
?
?
?
?
?
?
d
V
mass
?
or K
V
V
P
P
d
d
? ? ? ? .......
1
2
2
1
2
1
(E) At altitudes, as P is low d of air is less. That is why mountaineers carry oxygen cylinders.
(F) Air at the sea level is dense because it is compressed by the mass of air above it. However the density
and pressure decreases with increase in altitude. The atmospheric pressure at Mount Everest is only 0.5 atm.
Example : At constant temperature, if pressure increases by 1%, the percentage decrease of volume is
(a) 1% (b) 100/101% (c) 1/101% (d) 1/100%
Solution: (b)
2 2 1 1
V P V P ?
If mm P 100
1
? ,
2
P will be 101 mm
Hence
2
101 100 V V ? ? ? ,
V V ? ?
101
100
2
,
Decrease in volume
101
1
101
100
? ? ?
V
V of V i.e. %
101
100
Charle's law.
(A) French chemist, Jacques Charles first studied variation of volume with temperature, in 1787.
(B) It states that, “The volume of a given mass of a gas is directly proportional to the absolute temperature
) 273 ( ? ? C
o
at constant pressure”.
Thus, T V ? at constant pressure and mass
or ) 15 . 273 ) ( ( ? ? ? C t K KT V
o
, (where k is constant),
T1< T2< T3
T3
T2
T1
V or 1/d
P
O
T1< T2< T3
T3
T2
T1
1/V or d
P
O
T1< T2< T3
T3
T2
T1
P
PV
O
log P
O
log 1/V
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