Tuesday, 31 July 2012
Notes:Liquid State
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States of Mattre II(Liquid State)
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S.No
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SLO’s
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liquid state
Behaviors of Liquids:
The
liquids show the following behaviors or properties by which they are
distinguished from other substances.
1. Diffusibility:
Liquids can diffuse into one
another, they mix with each other to form a homogeneous mixture e.g. if a
drop of ink is added in water it spreads out in all direction, till a
homogenous colour mixture is formed. But the rates of diffusion are much
lesser than those of gases, because the liquids molecules have inter
molecular attraction and are not free to move like gases.
2. Compressibility:
Unlike gases, liquids are
normally incompressible. However, at very high pressure the volume of a
liquid is reduced very slightly.
This
behavior of liquids is due to the close packing of their molecules. The
molecules of liquids are so close to each other that the repulsions of
electron clouds resist all attempts at bringing tem further closer.
3. Expansion & Contraction:
Some of the liquids show
expansion on heating or they show increase in their volumes. The temperature
increases the K.E. of the liquid molecules increase due to this they move
apart, causing increase in volume or the liquid show expansion.
On,
the other hand on cooling liquids show decrease in their volumes, i.e. the
show contraction. It is due to cooling process, where thermal energy of molecules
is removed. This causes decrease in Kinetic energy of the molecules and
decreases in inter – spaces, and the liquid is contracted.
Viscosity:
It
is common observation that some liquids flow more readily than the other. For
example water moves over a glass plate more quickly than glycerine.
Similarly, honey and mobil oil flow more slowly than water. Hence, liquids
which flow easily are called “
“The internal
resistance to the flow of a liquid is called its viscosity”
Viscosity
is represented by ‘h’
and its unit is “POLSE”. Normally smaller units “CENTIPOISE” or “MILLIPOISE”
are used.
1
POISE = 1
gm/cm
&
1 POISE = 100 CENTIPOISE
= 1000 MILLIPOISE
Explanation:
Imagine a liquid flowing
through a tube and consists of concentric layers. The layers
in
contact with the walls of the tube remain almost stationary, whereas the
layers in the centre have the highest velocity and the intermediate layers
move with a gradation of velocities. Hence each layer exerts a drag on the
next layer which causes resistance to the flow.
The
liquid whose layers offer more resistance to its flow is more viscous than
the liquids whose layer offer less resistance. Therefore glycerine and honey
are more viscous than water, ether & alcohol.
Factors affecting Viscosity:
On
the following factors affect the viscosity of a liquid.
a) Molecular Size:
Viscosity
increases with increase in molecular size, because it is difficult for the
layer molecules to slide over another and to go from one layer to the other.
b) Molecular Shape:
An
irregular shape of molecules also causes the molecules to offer more
resistance than the molecules of regular shape. Thus the nonlinear molecules have
greater viscosity than linear ones.
c) Inter-Molecular Attraction:
Greater
the inter – molecular attraction in a liquid, greater will be force to resist
the flow. Thus the viscosity will also be higher.
d) Temperature:
Viscosities
of the liquids decrease with the increasing the temperature and vice-versa.
This is due to the increase of average K.E. of the molecules at higher
temperature.
Surface Tension:
“The inter-molecular force
that drawn the molecules on the surface of a liquid together causing the
surface to act like a thin elastic skin, this phenomenon is called SURFACE
TENSION”.
OR
“The
force per unit length or energy per unit area of the surface of a liquid is
called SURFACE TENSION”.
Surface
tension of the liquid is represented by
g OR
s,
and its units are dynes / cm OR erg / cm2.
Explanation:
 We
consider a molecule ‘A’ at the surface and ‘B’ inside the liquid. The
resultant force on ‘B’ is zero, because, it is attracted equally in all
direction. On the other hand, molecule ‘A’ is attracted laterally by
neighbouring molecules with equal forces. The molecule ‘A’ is also attracted
downward at right angle by the molecules underneath it. As there is no liquid
on its to balance the downward attractive forces, therefore, therefore the
molecules ‘A’ is pulled inside the liquid. A similar pull is also experienced
by other molecules on the surface of the liquid. However, the inward movement
of these molecules is not possible, because of the lateral forces of
neighbouring molecules. This creates a constant tension in the molecules of
the surface of the liquid, called “SURFACE TENSION”.
The surface of liquid thus
appears like a stretched membrane. It is so strong that a needle or a shaving
blade can float on it.
Factors Effecting Surface Tension:
The
surface tension of a liquid depends upon two factors:
a) Inter-Molecular Attraction:
Stronger
the inter-molecular attractive forces, greater is the surface tension, and
vise versa. For example, water possesses higher surface tension than most of
the organic solvents. This is because of strong inter – molecular forces in
water due to hydrogen bonding.
b) Temperature:
Surface
tension of a liquid also depends on temperature, it decreases with the
increase of temperature and vise – versa.
Vapours Pressure:
“The
Pressure exerted by the vapours of a liquid, in equilibrium state with the
pure liquid itself at a given temperature is called VAPOURS PRESSURE” of a
liquid”.
Explanation:
Consider
a volatile liquid in a closed container. Due to evaporation, the vapours are
accumulated in the space above the surface of the liquid. During their
motion, vapours lose a part of K.E. and are condensed again. After sometime,
the space above the surface of the liquid is saturated with vapours. At this
stage the rate of condensation becomes equal to the rate of evaporation. This
is called the “
Liquid Vapours
The
vapours due to their continuous state of random motion exert pressure on the
surface of the liquid. This pressure of vapours at the equilibrium is called
“Vapours Pressure”.
Boiling Point:
The vapours pressure of a
liquid increases with the increase in its temperature. A certain temperature
is reached when the vapours pressure of the liquid becomes equal to the
atmospheric pressure. At this temperature, the gas bubbles can be seen coming
out of the liquid. It is called the Boiling of the Liquid & the
temperature is called Boiling Point, so it can be defined as
“Boiling Point is
the temperature at which the vapours pressure of a liquid becomes equal to
the atmospheric pressure”.
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\
4. CRQs of Gaseous State
Numbericals:
1.
A mixture of Helium and Hydrogen
is confined in a 12dm3 flask at 30oC if 0.2 mole of the
Helium is present. Find out the partial pressure of each gas where the pressure
of mixture of gases is 2atm.
2. The
volume of the Oxygen gas collected over water at 24oC and 762 torr
(mm of Hg)
pressure
is 128 ml volume. Calculate the mass Oxygen gas
3.
13.2g of gass occupies a volume of
0.918dm3 at 25oC and 8atm pressure. Calculate the
molecular mass of the gas
4. 400cm3 of Helium gas take to
effuses from a porous container in 20 second. How long will be SO2
gas take to effuses from same container?
5.
A quantity of gas measure 500ml at
35oC and 600mm (Hg).
What would be the volume of the as at
45oC and 800mm (Hg)?
6
. 1.4dm3 volume of gas
measure at temperature of 27oC. and pressure 900 torr was
found to a mass
of gas 2.273g. Calculate the molecular mass of gas.
Three
container of equal volume are filled as follows.
a)2 mole of H2 gas at 0oC
b)1 mole of N2 gas at 273
K c) 3 mole of O2 gas at 27oC
7.
Calculate the molecular mass of a
gas whose rate of diffuse in twice of that of CH4
8. 380 cm3 of hydrogen gas was
collected over water at 23oC and 613 torr: find the volume of dry
hydrogen at S.T.P. (vapour pressure of water at 23oC is 21 torr.)
9. What is the volume of 2.5 mole of N2 gas at S.T.P.?
10. State the Dalton’s law of partial
pressure. A mixture of .2 mole of gas “A” and 1.1 gm of anther gas “”B” (mol.
Mass = 44) exerts a pressure of 750 torr: calculate the partial pressure of the
two gases.
11. A 500cm3 vessel contains H2
gas at 400 torr and another 1.0dm# Vessel contains O2
gas at 600 torr. If these gases are transferred to 2dm3 empty
vessel, calculate the total pressure of the mixture of the gases.
12. A given mass of a gas occupies 76 cm3
at 16oC and 760 torr pressure; calculate its volume at S.T.P.
13. A 100 cm3 gas, cylinder
filled with chlorine under 160 torr pressure is connected by stop-cock with another cylinder of 400
cm3 filled with nitrogen under pressure of 200 torr. What will be the total pressure
when stop cock is opened?
Assignments
Hand out #4.1.2
Q. 1Draw the plot from following data
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Pressure (atm)
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0.2
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0.25
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0.40
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0.60
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0.80
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1.0
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Volume (dm3)
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112
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89.2
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56.25
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37.40
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28.1
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22.4
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(a)volume against pressure (b)volume
against inverse of pressure (1/p)
Q.2 weather balloon has a volume of 175 dm3 when
filled with hydrogen at pressure of 1.00 atm. Calculate the volume of the balloon
where it rise to a height of 2000 m ‘where the atmospheric pressure is 0.800atm
.Assume that the temperature is constant.
Q.3 What is the volume of given mass of hydrogen at a
pressure of 2.50 atm , if it is volume
is 3.15 dm3 at 1.00 atm
Q.4 A sample of oxygen has a volume of 880 ml and pressure
of 740 torr .What addition pressure is required to reduce the volume to 440ml
Hand out # 4.2.1
Q. 1Draw the plot Volume and Absolute temperature from following data
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Temperature (K)
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135
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200
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270
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395
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450
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540
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Volume (dm3)
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250
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372
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500
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731
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838
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1000
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Q.2 A sample of helium of gas has volume of 520 cm3
at 373k . Calculate the temperature at which the volume will become 260 cm3
at constant pressure .
Q.3 A mass of Neon occupies 200cm3 at 100oC
.Find its volume at 0oC the pressure remain constant .
Q.4 Anesthetic gas is normally given a patients when the
room temperature is 20 oC and the patient s body temperature is 37o C. What would this temperature change do to 1600ml
of gas at constant pressure and mass remain
constant.
Q.5 What will be the volume at 450K of a gas which occupies
200cm3 at 300K the pressure remaining constant throughout.
Q.6 A sample of oxygen gas occupies 250 cm3at
300K.What volumes it will occupy at 35oC if there is no change in pressure.
Hand out 4.4.1
Q.1 What is the final volume of one mole of nitrogen
initially at S.T.P. If it is subjected to pressure of 2 atm and heated to a
temperature of 546 K
Q.2 7.0 gram of a gas at 300K and one atmospheric
pressure occupies a volume of 4.1 dm3.What is molecular mass of gas
.
Q.3 10.0 gram of oxygen gas are introduced in a vessel of 5
dm3 capacity at 27oC.Calculate pressure of the gas in atmospheric
pressure in the container.
Q.4 Two gas bulbs of the same size are mantainated at same temperature .bulb “A “contain Carbon
dioxide and bulb “B” Contain an equal mass of ethane .
(a)What is the ratio of the number of molecules in the
bulbs?
(b) What is the ratio of the pressures in the bulbs?
Q.5 A sample of nitrogen gas occupies a volume of 1.0 dm3
at pressure of 0.5 atm at 40oC .Calculate the pressure if the gas
compressed to 0.225 cm3 at -6oC.
Chapter # 04 Important Web site
Kinetic Molecular Theory:
http://preparatorychemistry.com/KMT_flash.htm
Ideal Gas Laws :
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/ideal_gas_law/interface.swf
Dalton's Law:
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/daltons_law/interface.swf
Molecular speed:
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/molecular_speed/interface.swf
Molecular motion :
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_10&folder=molecular_motion
Absolute Zero:
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_10&folder=molecular_motion
Henry's Law :
http://media.wwnorton.com/college/chemistry/chemtours/chapter_10/henrys_law/interface.swf
http://preparatorychemistry.com/KMT_flash.htm
Ideal Gas Laws :
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/ideal_gas_law/interface.swf
Dalton's Law:
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/daltons_law/interface.swf
Molecular speed:
http://media.wwnorton.com/college/chemistry/chemtours/chapter_06/molecular_speed/interface.swf
Molecular motion :
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_10&folder=molecular_motion
Absolute Zero:
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_10&folder=molecular_motion
Henry's Law :
http://media.wwnorton.com/college/chemistry/chemtours/chapter_10/henrys_law/interface.swf
Notes of Chapter # 04
SLOs
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Topic
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4.1
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Kinetic
Molecular Theory:
This
Theory describes the behavior of different stats of matter. However it is a
best model for an ideal gas. So, it is also called kinetic molecular theory
of gases.
The main postulates of this theory are
as given below:
Postulates:
1)
Gases are composed of a large number of particles
that behave like hard, spherical
objects in a state of constant, random motion.
2)
These particles move in a straight line until they
collide with another particle or the walls of the container.
3)
These particles are much smaller than the distance
between particles. Most of the volume of a gas is therefore empty space.
4)
There is no force of attraction between gas
particles or between the particles and the walls of the container.
5)
Collisions between gas particles or collisions
with the walls of the container are perfectly elastic. None of the energy of
a gas particle is lost when it collides with another particle or with the
walls of the container.
6)
The average kinetic energy of a collection of gas
particles depends on the temperature of the gas and nothing else.
7)
Gases exert pressure which the result of collision of molecule
of gas to the walls of container
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4.1.2
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GAS
LAW:
The gases have volume,
pressure, temperature etc. All these quantity are related to one and another
according to some statement, called “The gas laws”.. some of the important
gas laws are as follow:
ü Boyle’s law.
ü Charle’s law.
ü Avogadro’s
law.
ü Graham’s law
of diffusion.
ü Dalton’s law
of partial pressure.
Boyle’s
Law:
Robert
Boyle, in 1662, showed the relationship between the pressure and the volume
of a gas at constant temperature. This is called “BOYLE’S LAW.”
Statement
1:
According
to the Boyle’s law
“At
constant temperature, the volume of a given mass of gas is inversely
proportional to the pressure applied on it.”
Explanation:
It
means that the increase in pressure would result in a decrease of volume of a
gas, similarly the decrease in pressured result in the increase in the
volume.
Simply we can say, if the
pressure is doubled, the volume becomes half and if the pressure is reduce to
half, the volume becomes double.
Mathematic
Expression:
Mathematically, Boyle’s law can
be expressed
as
(at constant
temperature) ð P x V =K
Where K = proportionality constant.
This equation gives another
statement Boyle’s law, which is as under:
Statement
2:
“At
constant temperature, the product of pressure and a volume of a given mass of
a gas is always constant.”
Therefore; if
P1 & V1
are initial pressure & volume, &
P2 & V2
are changed pressure & volume,
Then P1V1=P2V2 This
is called “Boyle’s law equation
Graphical
Representation:
When
pressure’ P’ of a given mass of a gas is plotted against it’s volume ‘V’, a
parabolic curve is obtained, showing the decrease in volume in increasing
temperature. On the contrary, when
pressure ‘P’ of a given mass oa a gas is plotted against reciprocal pf volume
i.e.
 a straight line is
obtained. This confirms the direct relationship between ‘P’ and ‘’.
Limitations of Boyle’s law: This law is
not obeyed by gases under conditions of high pressure & law temperature.
CHARLE’S
LAW:
In
1787, a French physicist, Charles’s showed the relationship between the
volume of a given mass of a gas and it’s temperature at a constant pressure.
This law is called Charles’s law
STATEMENT # 1:
According
to this law:
“At constant pressure, the
volume of a given mass of a gas is directly proportional to the absolute temperature.”
EXPLAINATION:
It
means, if the pressure is kept constant, the increase in temperature would
result also in increase the volume of a given mass of a gas. Similarly, the
decrease in temperature results also in decrease in the volume of a gas.
MATHEMATICAL
EXPRESSION:
Mathematically, Charle’s law can be
expressed as:
VaT (At. Constant Pressure)
OR V=KT OR
This expression gives another
statement of Charle’s law, which is as under.
STATEMENT#2:
“At
constant pressure, the ratio of volume to the absolute temperature of given
mass of a gas is always constant.”
Therefore; if
V1&T1
are initial volume & temperature & V2 &T2
are changed volume & temperature.
Then
This is called “CHARLES’S law
equation.”
EXPERIMENTAL
VERIFICATION:
Consider
a gas cylinder fitted with a move able piston. The volume of the gas enclosed
in the cylinder is V1 at temp. T1 . When the gas is
heated to T2, its volume is increase to V2 by moving
the piston upward. It the pressure on the piston is kept constant, then it is
observed that the ratio between V1 andT1 is equal to
the ratio V2 and T2.i.e.
This verifies the Charle’s law.
     
-300
-200 -100 0 100
200 300
GRAHAM’S LAW
OF DIFFUSION:
Diffusion
is the natural process by which gases intermix with one another to form a
homogenous mixture.
In
1833, Graham established a relation ship between the rate of diffusion of
gases and their densities which is terms as “Gaham’s law of diffusion”.
STATEMENT:
According
to this law,
“The rates of
diffusion of gases are inversely proportional to the square root of their
densities under same condition of temperature and pressure”.
MATHEMATICAL Expression:
Mathematically,
graham’s law can be expressed as:
OR
Where r = rate of diffusion of gas,
d= density of gas,
K= Proportionality
constant.
Suppose two gases with densities d1
& d2, diffuse into each other. If the rate of diffusion of the
gases are r1 & r2 respectively, then according to
graham’s law:
For gas 1,
& For gas 2,
By
combining the two equations, we get
Since the density of a gas is
proportional to its molecular mass, so Graham’s law may also be expressed as:
Experimental Verification:
Take
a 100 cm long glass tube. Plug one end of it with a piece of cotton soaked in
NH3 solution and the other with a piece of cotton soaked in HCl
solution as shown in the diagram.
The
vapours of NH3 and HCl escape into the glass tube simultaneously.
A white ring of NH4Cl appears at the meeting point of the two gases.
Measure out the distance of te white ring from two ends.
Suppose,
the distance covered by NH3 = 60 cm
&
the distance covered by HCl = 40 cm
Since
the time ‘t’ is the same, therefore The rate of diffusion of NH3
gas =
&
the rate of diffusion of HCl gas =
\ Molecular Mass of NH3
=
 = 17
&
Molecular Mass of HCl =
 = 36.5
\ According to Graham’s law of
diffusion,
 
1.5 = 1.5
Since
L.H.S. = R.H.S., therefore Graham’s law of diffusion of gases is verified.
Dalton’s Law of Partial Pressure:
The
behavior observed, when two or more gases are placed in same container is
summarize in Dalton’s Law of Partial Pressure.
Statement: In 1801, Dalton’s found that
“The total pressure of a gaseous
mixture is the sum of the
partial pressure, exerted by each of the
gases present in
the mixture”.
Mathematical
Expression:
Mathematically
this law can be expressed as,
P
= P1 + P2 + P3 + ………………
Where
P =
Total pressure of gaseous mixture
P1 = Partial Pressure of gas 1.
P2 = Partial Pressure of gas 2.
P3 = Partial Pressure of gas 3.
Explanation:
When
two or more gases which do not react chemically, are mixed in the same container,
then each gas will exert the same pressure as it would exert if it alone
occupied the volume containing the mixed gases, under the same condition.
This portion of the total pressure of a mixture is known as PARTIAL PRESSURE.
Dalton observed that the total pressure of a mixture of different gases is
always equal to the sum of individual or partial pressure of each gas present
in a mixture.
Experimental
Verification:
Let
us suppose that two different gases A & B are confined in two separate
compartments as shown, in the figure. Both the compartments are of same size
with a pressure measuring device.
Now
suppose that the pressure of a gas is ‘A’ is 800 torr and that of gas ‘B’ is
900 torr in their separate compartments. If gas ‘A’ was transferred into the
compartment ‘B’ with the help of a movable piston through the total pressure
in this compartment would be the sum of the original pressure in the two
compartments when the gases were occupying same volume separately.
i.e. Ptotal = PA + PB
1700 = 800 + 900
1700 = 1700
Hence,
law is verified.
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4.1.3
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KMT
EXPLAINATION FOR BOYLE’S LAW
Boyle’s
law can easily be explained on the basis of the kinetic theory of gases, when
the volume of a given amount of a gas is decrease, there is more crowding of
the molecules in that space. This result in more frequent collision between
the molecules and the walls of the container and thus the pressure of the gas
is increased and vise-versa.
Limitations of Boyle’s law: This law is
not obeyed by gases under conditions of high pressure & law temperature.
KMT
EXPLAINATION FOR CHARLES’ LAW
This
law can be easily explained with the help of Kinetic molecular theory as:
An
increase in temperature increases the K.E. of gas molecules which results in
their more collision per second against the walls of the container. But if
the pressure is kept constant the extra force of the colliding molecules is
utilized for the expansion of gas, i.e. increase in volume.
KMT
EXPLAINATION FOR AVOGADRO ‘S LAW
It
means that, if we take different sample of different gases at same
temperature and pressure, then if the volume of each gas sample is equal, the
no. of molecules of each sample will be also equal evidently, if we increase
the volume of gas sample, the no, of molecules will be also increase.
Avogadro’s
also found that at the some condition of temperature and pressure, the one
mole of any gas occupies always 22.4dm3
volume, this volume is called molar gas volume. Also, this volume contain
always constant no. of particles of gas, and its value is 6.02 x 1023.
This value is called Avagadro’s number.
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4.2.1
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Charles’s
law can also be explained by graphical method, if the volume of the given
mass of a gas is plotted against its absolute temperature values at a
constant pressure, a straight line is obtained, showing the direct
relationship between ‘V’ and ’T’.
If
the straight line is extra plotted it intercepts the temperature axis at
-273.16oC. This temperature is called “ABSOLUTE ZERO”.
ABSOLUTE ZERO:
It
is a hypothetical temperature, at which the volume of all gases become zero.
Its value is -273.16oC.This temperature can never be achieved.
The
scale on which -273.16oC is taken as zero is called “KELVIN SCALE”
and is indicated by K. Centigrade is related to Kelvin scale as;
oK = oC
+ 273
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4.2.2
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NUMBERICAL
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4.3.1
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AVAGADRO’S LAW:
In
1811, Amadeo Avagadro stated the relation ship between the volume and the no.
of molecules of the gas. This is called “AVAGADRO’S LAW”.
Statement:
According
to Avogadro’s law;“The Volume of a gas is directly proportional to the number
of molecules of the gas at constant temperature & pressure”.
Explanation:
It
means that, if we take different sample of different gases at same
temperature and pressure, then if the volume of each gas sample is equal, the
no. of molecules of each sample will be also equal evidently, if we increase
the volume of gas sample, the no, of molecules will be also increase.
Avogadro’s
also found that at the some condition of temperature and pressure, the one
mole of any gas occupies always 22.4dm3
volume, this volume is called molar gas volume. Also, this volume contain
always constant no. of particles of gas, and its value is 6.02 x 1023.
This value is called Avagadro’s number.
Mathematical
Expression:
Mathematically,
Avogadro’s law can be written as,
V
µ
n
OR
V = K n
Where
n= no. of molecules of gas
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4.4.1
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General Gas
Equation:
Boyle’s
law, Charles law and Avogadro’s law may be combined together to give a
general relation between the pressure, volume, temperature and no. of moles
of a gas. This relationship is called “General
Gas Equation”
According to Boyle’s law
According to Charle’s law V µ T
On
combining these three laws. We get
OR
OR PV= nRT
This expression is called ‘GENERAL
GAS EQUATION’. Where ‘R’ is a proportionally constant and is called gas
constant.
For
1mole of a gas, n=1.
\PV=RT
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4.4.2
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When
the temperature of a gas changes from T1 to T2, then
its volume as well as pressure changes from V1 to V2
and P1 to P2.
\ For initial
state:
& For final state:
Combine
these two, we have
This
relationship is used to solve problems regarding changes of volume of gases,
due to the changes in the pressure & temperature.
VALUES &
UNIT’S OF ‘R’:
(a)
According to Avagadro’s law, at S.T.P the one mole
of any gas occupies a volume of 22.4dm3.
i.e. T=0˚C=273oK , P=1atm., n=1mole and V=22.4dm3
Then the value and unit of gas
constant will be;
   
(b)
When ‘P’ is expressed in
 and volume ‘V’ in m3,then at S.T.P,
P=101300
,V=0.0224m3 , n=1mol. And T=273oK.
Then the value and
unit of gas constant will be.
\
 
R
= 8.314 N.m / mole x K
R
= 8.314 J/mole x K
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4.4.3
|
U
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4.4.4
|
A
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4.5
|
4.5.1
|
Deviations
from ideal behavior
Ideal gas : a gas which obeys the general gas
equation and other gas laws under all conditions of temperature and pressure
is known as Ideal gas or perfect gas.
The molecules of an ideal gas :
(i)
Occupy negligible or no volume
(ii)
Have no inter-molecular
attractive forces.
Real gas : a gas
which does not obeys general gas
equation and all other gas laws strictly but tends towards ideality at low
pressure and high temperature is knonw as real gas .
Cause
of deviations from ideal behavior
In order to explain deviations from ideal behavior
,Vander waal pointed out that the following two assumptions in kinetic theory
are faulty.
(i)
The volume occupied by the gas
molecules themselves is negligible as compared to total volume of the gas
The above assumption
is nearly valid if the pressure is low .At low pressure ,the gas molecules
are widely separated and the free
space between the molecules is very large in comparison to the actual volume
of molecules of the gas. Under such condition, the volume of the gas
molecules can be neglected in comparison to the total volume. At the high
pressure, the molecules of gas are relatively closed together and the total
volume is significantly less . However
the actual volume of the gas
molecules remains unchanged because the gas molecules are
incompressible. Under these conditions, the volume of a real gas is larger than that for an ideal
gas.
(ii)
The molecules of a gas exert no
appreciable attraction upon each other .
This assumption is
nearly valid when the pressure is low and the temperature is high so
that the molecules are far away from
each other . if the pressure is high and the temperature is low , the volume
of the gas decrease .Gas molecules come closer to each other .The attractive
force between the gas molecules under
these conditions are quite appreciable and can not neglected .
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U
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4.5.2
|
Numerical for
ideal equation
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4.6
|
4.6.1
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4.7
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4.8
|
4.8.1
|
Plasma
state
Plasma is often called the “Fourth State of Matter”, the
other three being solid, liquid and gas. Plasma was identified by English
Scientist William Crookes in 1879. In addition to being important in many
aspects of our daily life , plasma are estimated to constitute more than 99
percent of visible universe. Although, naturally occurring plasma is rare on
Earth, there are many men –made examples.
Inventors
have used plasma to conduct electricity in neon signs and fluorescent bulbs
.Scientists has constructed special chambers to experiment with plasma in
laboratories. It occurs only in lighting discharges and in artificial devices
like fluorescent lights neon signs etc. It is everywhere in our space
environment.
When
more heat is supplied, the atoms or molecules may be ionized. An electron may
gain enough energy to escape its atom. This atom loses one electron and
develops a net positive charge ,It
become an ion .In a sufficiently heated gas, ionization happens many times
,creating clouds of free electron an ions .However, all the atoms are not
necessarily ionized ,and some of them may remain completely intact with no
net charge.
This ionized gas
mixture, consisting of ion, electron and neutral atoms is called PLASMA.
It means that a
plasma is distinct state of matter
containing a significant number of
electrical charged particle a number of electric
Reference from:
Topic # 3.11 Page #73 of Chemistry 11 PUNJAB TEXTBOOK BOARD,LAHORE
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