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TRANSCRIPT
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N.P.R. COLLEGE OF ENGINEERING AND
TECHNOLOGY
DEPARTMENT OF CHEMISTRY
ENOTES
Subject Name : ENGINEERING CHEMISTRY I
Subject Code : 10ACH01
Year : I Year (Common to all branches)
Semester : I
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10ACH01 ENGINEERING CHEMISTRY
UNIT I WATER TECHNOLOGY
Water Types Alkalinity types of alkalinity and determination
hardness types CaCO3 equivalents Estimation by EDTA method(problems)Boiler feed waterrequirementsDisadvantages of using
hard water in boiler Internal conditioning(Phosphate, Carbon and
Carbonate)External conditioningZeolite processDemineralization
processDesalinationReverse Osmosis (Chlorination, UV
treatment, ozonation).
UNIT II POLYMERS AND COMPOSITES
PolymersTypesPolymerizationAddition and condensation
polymerizationFree
radical polymerization mechanismPlasticsclassification-
preparation, properties and
uses of PVC, Teflon, Polyurethane, Nylon 6:6, PET, Bakelite, and
Epoxy resin
Compounding of Plastics- Compression mouldingInjection moulding
Composites
definitiontypes of Polymer matrix compositesFRP only.
UNIT III SURFACE CHEMISTRY
AdsorptionTypesAdsorption of gases on solidsAdsorption
isothermsFreundlich
and Langmuir isothermsAdsorption of solids from solutionRole of
adsorption in
catalysis - Ion exchange adsorptionPollution abatement.
UNIT IV NON CONVENTIONAL ENERGY SOURCES AND
STORAGE DEVICES
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Nuclear energyfission and fusion reactionsLight water nuclear
reactor for power
generation (Block diagram only)Breeder reactorSolar energy
conversionSolarcellsWind energyFuel cellsHydrogenOxygen fuel cell
BatteriesAlkaline
batteriesLead acid storage batteryNickelCadmium and Lithium
batteries.
UNIT V ENGINEERING MATERIALS
RefractoriesClassification-( acidic, basic and neutral)Properties
(refractoriness,
refractoriness under load, porosity, dimensional stability, thermal
spalling)manufacture
of alumina, magnesite and Zirconia bricksAbrasivesNatural
abrasives(Quartz,
corundum, emery, garnet, diamond)Artificial abrasives (silicon
carbide, boron carbide)
Lubricants- Mechanism of lubricationLiquid lubricantsProperties
(Viscosity,
viscosity index, flash and fire points, cloud and pour points, oilness ,
aniline number)
solid lubricants (graphite & molybdenum disulphide).
TEXT BOOKS:
1. Engineering Chemistry, P.C.Jain and Monica Jain, Dhanpat Rai
Pub, Co.,New Delhi (2002).
2. A text book of engineering chemistry, S.S. Dara S.Chand &
Co.Ltd.,
New Delhi (2006).
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REFERENCES:
1. Engineering chemistry, B.K.Sharma Krishna Prakasan Media (P)
Ltd.,
Meerut (2001).2. Engineering Chemistry, B. Sivasankar ,Tate McGraw-Hill
Pub.Co.Ltd,
New Delhi (2008).
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UNIT I WATER TECHNOLOGY
Water Types Alkalinity types of alkalinity and determination
hardness types CaCO3 equivalents Estimation by EDTA method
(problems)Boiler feed waterrequirementsDisadvantages of usinghard water in boiler Internal conditioning(Phosphate, Carbon and
Carbonate)External conditioningZeolite processDemineralization
processDesalinationReverse Osmosis (Chlorination, UV
treatment, ozonation).
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Unit-1 Water Technology
The process of removing all types of impurities from water of
impurities from water and making fit for domestic (or)industrial
purpose is called water technology.
Types of impurities in water:
The impurities present in water may be broadly classified into three
types
(i)Physical impurities
(a)Suspended impurities(b) Colloidal impurities
(ii) Chemical impurities
(a)Dissolved salts
(b)Dissolved gases
(iii) Bacterial impurities
Boiler feed water
The water fed into the boiler for the production of steam is called boiler
feed water.
Requirements
Boiler feed water should be free from turbidity, oil, dissolved gases,
alkali and hardness causing substances.
Hard water:
Which does not produce lather with soap soln,but produce white
ppt(scum) is called hard watetr.
2C17H35COONa +Ca++
(C17H35COO)2Ca + 2Na+
Soft water:
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Which produce lather readily with soap soln is called soft water.
Absence of Ca&Mg salts.
Types of hardness:
1.Temporary hardness
2.permanent hardness
Units of hardnss:
Parts per million(ppm)
It is defined as the no.of parts of CaCo3 eqivalent hardness per10
6parts of water.
Milligram per litre(mg/lit)
It is defined as the no.of milligrams of CaCO3 equivalent
hardness per 1 litre of water.
Clarkes degree( Cl)
It is defined as the no.of parts of CaCO3 equivalent hardness
per 105
parts of water.
French degree( Fr)
It is defined as the no.of parts of CaCO3 equivalent hardness per
105
part of water.
1ppm=1mg/lit=0.10Fr=0.070cl
Alkalinity determination:
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PRINCIPLE
Alkalinity in water is due to the presence of soluble hydroxides,
bicarbonates and carbonates. Alkalinity can be determined by
Potentiometric methods
Using pH meter
Titrimetry using different indicators
Determination of various types and amounts of alkalinity is easily
carried out by titration with standard HCl employing the indicators
phenolphthalein and methyl orange independently or in succession.
The following reactions occur when different types of alkalinity are
neutralized with acid.
OH- + H+ H2O completed at pH 8.2-9.0 ----------- (1)
CO32- + H+ HCO3- -------------- (2)
HCO3-
+ H+ (H2CO3) H2O + CO2 , completed at pH
4.2-5.5---(3)
Neutralisation (1) & (2) will be notified by phenolphthalein end-
point while all the three will be accounted by methyl orange end-
point. Bicarbonate in eqn (3) may be due to the existence of soluble
free bicarbonate salts or bicarbonates resulting from half
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neutralization of soluble carbonates (eqn. (2))Various steps to be
followed:
A known volume of water sample is titrated against std. HCl using first
phenolphthalein indicator till end-point (P) and the titration is
continued without break using methyl orange indicator till the
equivalence end-point (M).
From the magnitudes of the P & M, the nature of alkalinity can be
arrived as follows:
(i) P = M => Presence of only OH-
(ii) 2P = M => Presence of only CO32-
(iii) P =0, M#0 => Presence of only HCO3-
(iv) 2P > M => Presence of OH- & CO32-
(v) 2P < M => Presence of HCO3-& CO3
2-
(Mixture of OH- & HCO3-are not listed since they do not exist
together and are considered equivalent to CO32-
).
PROCEDURE
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TITRATION I
STANDARDISATION OF HCl
Exactly 20 ml of the given standard NaOH solution is pipetted out intoa clean conical flask and 2 drops of phenolphthalein indicator is added.
The solution is titrated against the given HCl taken in the burette. The
pink colour of the solution in the conical flask disappears at the end-
point. The titre value is noted down from the burette and the titration
is repeated to get concordant value.
TITRATION II
ESTIMATION OF ALKALINITY IN WATER SAMPLE
Exactly 20 ml of water sample is pipetted out into a clean conical
flask. Few drops of phenolphthalein indicator are added and titrated
against the standardized HCl taken in the burette. The end-point is the
disappearance of pink colour, which is noted as P. Into the same
solution few drops of methyl orange indicator is added. The solution
changes to yellow. The titration is continued further by adding same
HCl without break till the end-point is reached. The end point is the
colour change from yellow to reddish orange. The titre value is noted
as M.
The experiment is repeated to get concordant values. From the
magnitudes of P & M values, the type of alkalinity present in the
water sample is inferred and the individual amounts are calculated
and reported.
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Estimation of hardness by EDTA method:
EDTA:ethylene diammine tetra acetic acid
(CH2COOH )2N-CH2-CH2-N(CH2COOH)2
Principle:
Hadness causing ions (Ca2+,mg2+)estimatimated by titrating the
water sample against EDTA.
Indicator: eriochromeblackT
Buffer soln: (NH4Cl-NH4OH):PH:8-10
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*Ca2,Mg2+EBT*Ca,Mg EBT+ complex(wine red
coloured weak complex)
*Ca ,Mg EBT+Complex EDTA*Ca Mg EDTD+EBT(Steel
blue)
The estimation is based on the complexometric titration.
(i) Total hardness of water is estimated by titrating it
against EDTA using EBT indicator.
EBT+Mn+[EBT-M] (complex)
EBT-M (unstable complex) +EDTA [EDTA-M] (stable complex)
+EBT
(Wine red) (Steel blue)
EBT indicator forms wine red coloured complex with hardness
causing metal ions present in water. On addition of EDTA, metal ions
preferably form complexes with EDTA and steel blue EBT indicator
is set free. Therefore change of colour from wine red to steel blue
denotes the end point.
(iii) Temporary hardness is removed by boiling the water.
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Ca (HCO3)2 CaCO3CO2 +H2O
Mg (HCO3)2Mg(OH)2 2CO2
The precipitate is filtered and the remaining permanent
hardness is estimated using EDTA.
Pipette out 20ml of standard CaCl2 into a 250ml conical flask.
(Standard hard water is prepared by dissolving 1 g of calcium
carbonate in one litre of distilled water) . Add 5ml of buffer solution
and 3 drops of eriochrome black T indictor. Titrate the solution with
EDTA from the burette until the colour changes from wine red to
steel blue at the end point. Repeat the titration for concordant
values. Let the titre value be V1ml.
TITRATION II
(ii) DETERMINATION OF TOTAL HARDNESS
Pipette out 20ml of sample hard water into a clean conical flask.
Add 5ml of buffer solution and 4 -5 drop of eriochrome black T
indicator. Titrate the wine red coloured solution with EDTA from the
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burette until the colour steel blue appears at the end point. Repeat
the titration for concordant values. Let the titre value be V2ml.
TITRATION III
(iii)DETERMINATIONOF PERMANENT HARDNESS
Take 250ml of hard water sample in a 250ml beaker and boil gently
for about 20 minutes. Cool, filter it into a 250ml standard flask and
make the volume upto the mark. Take 20ml of this solution and
proceed it in the same way as in titration (I). The volume of EDTA
consumed corresponds to the permanent hardness of the water
sample. Let the titre value be V3ml. Temporary hardness is
calculated by subtracting permanent hardness from total hardness.
Step 1- Arriving at standard equation,
1ml of Std CaCl 2 = 1 mg of CaCO3 ( given)
V1 ml of EDTA = 20 ml of Std. CaCl 2
1 ml of EDTA = (20 / V1) ml of Std. CaCl 2
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Therefore, ml of EDTA = (20 / V1) mg of CaCO3 (standard
equation.)
Step 2.- Calculation of total hardness.
Volume of EDTA consumed (V2) =-------- ml
20ml of sample hard water = V2 ml of EDTA
1000 ml of sample hard water =V2X(1000/20) ml of EDTA
As per standard equation,100ml of given hard water
= V2 X (1000/20) X (20 / V1) mg of CaCO3
=1000 x (V2 / V1 ) mg of CaCO3
Therefore, total hardness = ----------ppm
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Step 3.- Calculation of permanent hardness.
Volume of EDTA consumed (V3) =-------- ml
20ml of boiled water = V3 ml of EDTA
1000 ml of boiled water =V3 X (1000/20) ml of EDTA
As per standard equation,
1000ml of given hard water= V3 X (1000/20) X (20
/V1) mg of CaCO3
= 1000 x (V3 / V1 ) mg of CaCO3
Therefore, permanent hardness = ----------ppm
Step 4 Calculation of temporary hardness
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Temporary hardness of the given sample of water = Total hardness
Permanent hardness
=ppm
Treatment of water for domestic supply :
Screening:
It is a process of removing the fioating material like
leaves,woodpieces,etc.from water.
Aeration:
The process of mixing water with air is known as aeration.
To remove gases like CO2,H2S
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Sedimentation:
It is a process of removing suspended impurities by allowingthe water to stand un disturbed for 2-6 hours in a big tank.
Coagulation:
In this method certain chemicals called coagulats,like alum,
Al2(SO4)3+6H2OAl(OH)33H2SO4
Filtration :
It is the process of removing
bacteria,colour,taste,odour.passing water through filter beds.
Sterilization(or)disinfection:
The process of destroying the harmful bacteria is known assterilization.
By boiling:
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Water boiled for 10-15minitues all the harmful bacteria are
killed and the water becomes safe for use.
By ozonation
O3O2+[O]
Ozone is a powerful disinfectant and is readily absorbed by water,
By using UV radiation
Using for sterlisizing water in swimming pool.
Cl2+H2OHClHOCl
Cl2+NH3ClNH2+HCl
ClNH2+H2OHOClNH3
CaOCl2+H2OCa(OH)2+Cl2
Cl2+H2OHClHOCl
HOClBacteriabacterias are killed
Break point chlorination:
Water contains following impurities:
1.bacterias
2.organic impurities
3.redusing substances(Fe2+,H2S etc)
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4.Free ammonia
Boiler feed water:
The water feed into the boiler fo the production of steam is calledboiler feed water
Boiler troubles: 1.scale&sludge formation
2.priming&foaming
3.caustic embrittlement
4.boiler corrosion
Sludge: if the ppt is loose and slimy it is called sludge .sludge are
formed by substances like mgcl2,mgso4,cacl2
Scale: if the ppt forms hard&adherent coating on the inner walls of
the boiler like Mg(OH)2,caso4
S.NO sludge scale
1 sludge is a loose ,slimy and non
adherent precipitate.
scale is a hard,adherent coating.
2 The main sludge forming
substance are MgCO3,CaCl2 etc.
The main scale forming substances
areca(HCO3)2,Mg(OH)2
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3 Disadvantages:sludge are poor
conductors of heat.excess of
sludge formation decreases the
efficiency of boiler.
Disadvantages: scales act as a thermal
insulators.it decreases the efficiency of
the boiler.
4 sludge formation can be
prevented by using softened
water.
Sludge can also be removed by
using blow down operation.
scale formation can be prevented by
dissolving using acids like HCl,H2SO4
scale formation can also be removed by
external,internal treatment.
Priming&foaming:
Priming is the process of production of wet steam .priming is casued by
1.high steam velocity
2.very poor boiler design .
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Foaming (the formation of stable bubbles above the surface of
water is called foaming.
Foaming is caused by presence of oil.&grease.presence of finely
divided particle.
Caustic embrittlement:
It means intercrystaline cracking .boiler water containsNa2co3
Na2co3+H2O2NaOHCO2
Fe2NaOHNa2Feo2+H2
Boiler corrosion:
Corrosion in boilers is due to the presence of
1.Dissolved o2
2.Dissolved CO2
3.Dissolved salts
4Fe+6H2O+3O24Fe(OH)3
2Na2SO3+O22Na2SO4
N2H4+O2N2+2H2O
Mechanical de-aeration method:
The high temperature &low pressure produced inside the tower
dissolved oxygen content of the water.
CO2+H2OH2CO3
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2NH4OH+CO2 (NH4)2CO3+H2O
MgCl2+2H2OMg(OH)2+2HCl
Fe2HClFeCl2+H2
Softening(or)conditioning method:
The process of removing hardness producing salts from
water is known as softening(or)conditioning of water.
This method can be done in 2 methods
1.External conditioning
2.Internal conditioning
External conditioning:
Ion exchange (or)demineralization process.
Cation exchanger:
Resins contains acidic functional groups (COOH,SO3H) cation
exchange resin is presented as RH2
ex: 1.sulphonated coals.
2.sulphonated polystyrene RSO3H
Anion exchanger
Resin contain basic functional groups (NH2,OH)Anion exchange
resin is representated as R(OH)2
RH2+CaCl2RCa2HCl
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RH2+mgso4RmgH2SO4
RHNaClRNaHCl
Regeneration:
RCa2HClRH2+CaCL2
RNaHClRHNaCl
RCl22NaOHR(OH)2+2NaCl
Carbonate conditioning: scale formation can be avoided by adding
Na2CO3 to the boiler water.
CaSO4+Na2CO3CaCO3+Na2SO4
Phosphate conditioning: scale formation can be avoided by adding
sodium phosphate.
3CaSO4+2Na3po4Ca3(po4)2
Trisodiumphospate Na3po4(Weaklyalkaline) used for too acidic water.
Disodium hydrogen phosphate-Na2HPO4(weakly alkaline) used for alka
weakly acdic water.
Sodium dihydrogen phosphate-NaH2PO4(acidic) used for alkaline
water.
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Calogen conditioning
Calogen is sodium hexa meta phosphateNa2[Na4(PO3)6]
2Caso4+Na2[Na4(po3)6+Na2[Ca2(PO3)6]+2Na2SO4
The complex Na2[Na4(po3)6] is soluble in water and ther is no problem
of sludge disposal. So calogen conditioning is better than phosphate
conditioning.
Zeolite process:
Hard water contains Ca2
+&Mg2
+ ions this ions form hard soap(in soluble)with soap which does not produce lather with soap soln.
Hard water is softened by passing it through a column packed with
sodium cation exchange resin (called sodium zeolite )
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Na2Ze+Ca2CaZe2Na
Synthetic zeolite is represented by Na2Ze. The sodium ions which are
loosely held in Na2Ze are replaced by Ca2+
and Mg2+
ions present in the
water.
Process:
Sodium ions with Ca2+
and Mg2+
ions present in the water to form Ca
and Mg ions present in the water.
Ca(HCO3)+Na2Ze CaZe2NaHCO3
Mg (HCO3)+Na2Ze MgZe2NaHCO3
CaSO4+ Na2Ze CaZeNa2SO4
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Mg SO4+ Na2Ze Mg ZeNa2SO4
CaCl2 +Na2Ze CaZe2NaCl
Mg Cl2 +Na2Ze Mg Ze+2NaCl
Regeneration:
CaZe+2Na+Cl
-Na2Ze+CaCi2
Desalination of brackish water:
The process of removing common salt from the water is
known as desalination.
1.Fresh water -1000ppm but 35000ppm of dissolved solids.
Reverse osmosis(RO)
Two solns of different concentrations are separated by a semi
permeable membarane.
Flows from a region of lower concentration to higher concentration.
This process is called osmosis .
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Solvent flows from higher concentration to lower
concentration.this is called reverse osmosis.
Advantages:
1.The life of the membarane is high ,and it can be replaced with in
few minutes.
2.It removes ionic as well as nonionic ,colloidal impurities
3.Due to low capital cost,simplicity.
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Unit-I
Part A
1. Define hardness of water.
2. What are the salts responsible for carbonate and non-carbonate hardness of
water?
3. What is meant by soft water and hard water?
4. Distinguish hard and soft water.
5. How the hardness of water is expressed?
6. Give the significance of calcium carbonate equivalent.
7. How does EBT indicator function as an indicator in EDTA titration?
8. What is meant by permanent hardness of water?
9. Define alkalinity?
10. How is alkalinity classified?
11. How is alkalinity determined?
12. Why water is softened before using in boilers?
13. What are scales and sludges?
14. What is meant by priming and foaming?
15. How the caustic embrittlement is prevented?
16. Indicate the reasons for boiler corrosions.
17. Define softening of water. How it is carried out?
18. Soft water is demineralised water (DM) where as DM water is a soft water.Justify.
19. What is sodium Zeolite?
20 (a). What is aeration of water/Mention its uses?
(b). What is calgon conditioning?
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(c). Explain the term break point chlorination.
(d). What is desalination?
(e). What is blow down operation?.
(f). How hardness of water is removed in zeolite process?
Part-B
1. Describe the principle and method involved in the determination of different
types and amount of alkalinity of water.
2. Explain the EDTA method of estimation of hardness of water.
3. What are boiler troubles? How are they caused? Suggest steps to minimize the
boiler troubles.
4. What is potable water? What are the steps taken to obtain pure drinking
water?
5. How is internal treatment of boiler water carried out?
6. What is desalination? Name the different methods of desalination. Explain the
reverse osmosis in detail.
7. Discuss the chlorination, ozonation and UV methods of disinfection.
8. Explain Zeolite process in detail.
9. Explain the process of sterilization of domestic water supply?
10.(a) 100ml of a water sample requires 20ml of EDTA solution for titration. 1ml
of EDTA solution is equivalent to 1.1mgs of CaCO3. Calculate the hardness in ppm.
(b).In an estimation of hardness of water by EDTA titration 250 ml of a sample
water require 15ml of 0.025M EDTA solution to get the end point. Calculate the
hardness of water.
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UNIT II POLYMERS AND COMPOSITES
PolymersTypesPolymerizationAddition and condensation
polymerizationFree
radical polymerization mechanismPlasticsclassification-preparation, properties and
uses of PVC, Teflon, Polyurethane, Nylon 6:6, PET, Bakelite, and
Epoxy resin
Compounding of Plastics- Compression mouldingInjection moulding
Composites
definitiontypes of Polymer matrix compositesFRP only.
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Unit-2
POLYMER
Polymer: polymers is macromolecules formed by the repeated
linking of large no.of small molecules called monomers.
Monomers:
nCH2=CH2 (-CH2-CH2-) n
Ethylene Polyethylene
Monomer:
Monomer is a micromolecule which combines with each other to
form a polymer.
EX:
CH2=CH2(Monomer) -CH2-CH2- (repeating unit)
Polymerization
Polymerization is a process in which large no.of small molecules
combine to form a big molecule with (or)with out elimination of small
molecules like water.
Degree of polymerization:
The no .of repeating unit in a polymer chain is known as degree
of polymerization.
3CH2=CH2-CH2-CH2-CH2-CH2-CH2-CH2-
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Tacticity:
The orientation of monomeric units(or)functional groups in
polymer molecule can take place in a orderly (or)disorderly manner
with respect to the main chain is known as tacticity.
Functionality:
The no.of bonding sites (or)functional groups present in a
monomer is known as its functionality.
1.bifunctional monomer
2.Trifunctional monomer
3.polyfunctional monomer
Ex:poly ethylene,poly propy lene
..-M-M-M-M-M-M-M-M-M-M-M.
Copolymer (Heteropolymer) :
A polymer containing more than one type of monomer is known
as copolymer.
Ex: nylon ,terylene.
-M1-M2-M1-M2-M1-M2-M1
Hetero chain polymer:
If the main chain of a polymer is made up of different
atoms.
Ex: nylon 6:6 . ...C-C-O-C-C-O -C-C
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Addition(or)chain growth polymerization :
It is a reaction that yields a polymer ,which is an exact multiple of
the original monomeric molecule contains one(or)more double
bond.in addition polymerization there is no elimination of any
molecule.
Ex:polyethylene is produced from ethylene
nCH2=CH2 n.CH2-CH2.-(CH 2-CH2-)n
ethylene polyethylene
Ex: pvc is produced from vinyl chloride
nCH2=CH-Cl - nCH2- CH . (-CH2-CH-Cl)n
vinyl chlori de | PVC
cl
Bifunctional monomer
EX: PAN is produced from acrylonitrile
nCH2=CH-CN . CH2-CH - .. (CH2-CH-CN-)n
|
CN
Acrylonitrile Bifunctional monomer PAN
Condensation polymerization
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It is a reaction between simple polar groups containing
monomer with the formation of polymer and elimination of small
molecule like H2O
Hexamethylene diamine react with adipic acid condense to form of
nylon6:6
nH2N(CH2)6NH2 +n HOOC(CH2)4 -COOH -[HN-
(CH2)6NHCOCH2- CO -]n(Nylon 6:6)
copolymerization:
it is the joint polymerization in which 2(or) more differentmonomers combine to give a polymer.
nCH2=CHCH =CH2 +n CH2= CH -(CH2-CH=-CH-CH2-CH2-CH-)
| |
C6H5 C6H5
Butadiene styrene polybutadiene co
styrene
Plastics
Plastics are high molecular organic material that can be moulded
into any desired shape by the application of heat and pressure in the
presence in the presence of a catalysit.
Classification of plastics:
1.Thermopiastics ex:pvc, polyethylene
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2.Thermosetting plastics ex:Bakelite, polyester
Thermoplastic resin:
Thermoplastic can be softened on heating and hardened oncooling. They are generally soluble in organic solvent.
Ex: pvc, polyethylene
Thermosetting resin
Theremosetting plastics are prepared by condensation
polymerization.this plastics get harden on heating and once harden
cannot be softened again.
Ex;Bakelite,polyester.
s.no Thermoplastic resins Thermosetting resins
1 They are formed by addition
polymerization
They are formed by
condensation polymerization.
2 The cnsist of linear long
chain polymer.
They consist of three
dimentional network structure.
3 They are weak,softand less
brittle.
They can be remoulded
They are strong,hard and more
brittle.
They can not be remoulded.
4 They soften on heating and
harden on cooling.
They do not soften on heating.
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Engineering plastics :
Engineering plastics are a group of materials obtained from high
polymer resins ,they posses high mechanical strength,toughness.
Ex:pvc,Teflon,PET,Nylon 6:6
Preparation of pvc:. Pvc obtained by heating water emulsion of vinyl
chloride in the presence of benzoyl peroxide.
nCH2 =CHCl ( -CH2-CH-) catalyst:H2O2
|
Cl
Vinylchloride polyvinylchloride
properties: PVC is chemically inert powder. Insoluble in acids and
alkalies and undergoes degradation in presence of light.
Uses:
1. It is used in the production of pipes,cable insulator,table
cover,rain coat etc.
2. It is also used for making sheets,light fittings etc.
Teflon:
Teflon obtained by polymerization of water emulsion of
tetrafluoroethylene in presence of benzoyl peroxide under pressure.Tough, high softening point (350
0C), very high chemical inertness and
thermal stability
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( C6H5CO)2O2
n CF2=CF2 ( -CF2-CF2-) n
Tetrafluroethylene Teflon
Properties:
Teflon is extremely tough,flexible materials possing high softening
point.
It possees extremely good electrical and mechanical properties
Uses:
1.it is used as a very good electrical insulating material in
motors,cables.
2.it is also used for making gaskets ,packing,pump pa rts.
3.it is used in making non sticking stop cocks for burettes.
Perlon-U:
It is obtained by the reaction of 1,4,butanediol with
1,6hexamethylene di- isocyanate
O=C=N-(CH2)-N=C=O + HO-(CH2)4-OH
1,6Hexamethylene di-isocyanate 1,4butane diol
polymerisation
n [-O=C-HN-(CH2)6-NH-COO-(CH2)4-OH ]
( perlon-U)
Properties:
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It is less stable than polyamide.
It is easily affected by moisture.
It is characterized by excellent resistance to abrasion and solvents.
Uses:
1.perlonU Is used as coatings,films foams,adhesives&elastomer.
2.They are aiso used in defence,oceanographic research.
3.The are aiso used in foundation garments &swim suits.
Nylon 6:6
Nylon 6:6 is obtained by the polymerization of adipic acid &hexa
methylenediamine
n H2N-(CH2)-NH2 + nHOOC-(CH2)4-COOH
[-HN-(CH2)6-NHCO-(CH2)4-CO-]n
Nylon6:6
Properties:
Nylons are translucent, whitest,horny andhigh melting polymers.
They are insoluble in common organic solvents and soluble in phenol
and formic acid.
Uses:
1.Nylon 6:6 are used for making filaments for ropes ,bristles for
tooth b rushes etc.
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2.Nylon 6:6 is used for fibres,which is used in making
socks,carpets.etc
PET(poly ethylene terephalate)
Preparation
It is a saturated polyester,prepared by condensation of ethylene
glycol and terephthalic acid.
Properties
It is a good fibre forming material and is converted into commercialfibres.
The fibres posses high stretch resistance ,highcrease and wrinkle
resistance.
Uses
It is mostly used for making synthetic fibres like terylene.etc.
It is used for blending with wool,to provide better crease and wrinkle
resistance.
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Bakelite
It is obtained by the condensation polymerization of phenol and
formaldehyde in the presence of acid (or)alkali catalyst.
Step 1
Methylolation
The first step is the reaction between phenol and
formaldehyde,forms mono,di and tri methylol phenols.
Stepii
Formation of A stage resin (resole)
Resole is a low molecular weight linear polymer.
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Formation of Bstage resin(novolac(or)resitol
Novolac is high molecular weight linear polymer.
Production of C stage resin(Bakelite)
Further heating of A stage resin (or)B stage resin (or) both in the
presence of a curing agent produces hard ,rigd ,crosslinked
polymer called Bakelite.
Properties
Bakelite is resistant to acids ,salts and most organic solvent,but it
is attacked by alkalis because of the presence ofOH groups.
Uses
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Bakelite is used as an adhesive in plywood lamination and in grinding
wheelsw ,etc.
It is also widely used in paints,varnishes.
Epoxide (epoxy resins
Preparation
Epoxy resins are important thermosetting synthetic resins. They are
polyethers ,prepared by the condensation of epichlorohydrin with
bisphenol-A
Properties
Epoxy resin adhesives are thermosetting resins and posses good
adhesives properties.
They have good chemical and electrical resistance.
Uses
Epoxy resins are used to bind number of substances including metals
and glasses.
Epoxy resin adhesives are sold in the market as in the name of
araldite.
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.
Compounding of plastics:
Compounding of plastics is a process by which polymer resi
ns are mixed with some additives like fillers ,plasticizers etc .
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Fabrication of plastics :
Fabrication involves conversion of polymeric materials into
desired shape.many methods are employed for the fabrication
which depants on the types of plastics.
Moulding process:
The process involes fabrication of plastics materials into desired
shape under the influence of heat and pressure in
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theclosedchamber1.compression moulding
This method applied to both thermoplastics and thermosetting
plastics.this method mould is made up of two halves .the material to
be mouleded is placed in the cavity care fully under low pressure.
Finally the moulded is heated to 100-2000
C. after curing the
moulded article is taken out by opening the mould parts.
Injection moulding:
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This method is mainly applicable to thermoplastic .the powdered
plastic material is fed into the heated cylinder through the hopper .the
plastic material melts under the influence of heat and becomes fluid.
The mould is kept cold to allow the hot plasic to cure and
becomes rigd.telephone,buckets etc. are made by this method.
COMPOSTIES AND FRP
The most primitive composite materials were straw and mud combined
to form bricks for building construction; the Biblical Book of Exodus
speaks of the Israelites being oppressed by Pharaoh, by being forced to
make bricks without straw being provided. The ancient brick-making
process can still be seen on Egyptian tomb paintings in the Metropolitan
Museum of Art. The most advanced examples perform routinely on
spacecraft in demanding environments. The most visible applications
pave our roadways in the form of either steel and aggregate reinforced
portland cement or asphalt concrete. Those composites closest to our
personal hygiene form our shower stalls and bath tubs made of
fiberglass. Solid surface, imitation granite and cultured marble sinks and
counter tops are widely used to enhance our living experiences.
Composites are made up of individual materials referred to as
constituent materials. There are two categories of constituent materials:
matrix and reinforcement. At least one portion of each type is required.
The matrix material surrounds and supports the reinforcement materials
by maintaining their relative positions. The reinforcements impart their
special mechanical and physical properties to enhance the matrix
properties. A synergism produces material properties unavailable fromthe individual constituent materials, while the wide variety of matrix and
strengthening materials allows the designer of the product or structure to
choose an optimum combination. Engineered composite materials must
be formed to shape. The matrix material can be introduced to the
reinforcement before or after the reinforcement material is placed into
http://en.wikipedia.org/wiki/Strawhttp://en.wikipedia.org/wiki/Mudhttp://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Biblehttp://en.wikipedia.org/wiki/Book_of_Exodushttp://en.wikipedia.org/wiki/Israeliteshttp://en.wikipedia.org/wiki/Pharaohhttp://en.wikipedia.org/wiki/Bricks_without_strawhttp://en.wikipedia.org/wiki/Art_of_Ancient_Egypt#Paintingshttp://en.wikipedia.org/wiki/Metropolitan_Museum_of_Arthttp://en.wikipedia.org/wiki/Metropolitan_Museum_of_Arthttp://en.wikipedia.org/wiki/Portland_cementhttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Asphalt_concretehttp://en.wikipedia.org/wiki/Portland_cementhttp://en.wikipedia.org/wiki/Metropolitan_Museum_of_Arthttp://en.wikipedia.org/wiki/Metropolitan_Museum_of_Arthttp://en.wikipedia.org/wiki/Art_of_Ancient_Egypt#Paintingshttp://en.wikipedia.org/wiki/Bricks_without_strawhttp://en.wikipedia.org/wiki/Pharaohhttp://en.wikipedia.org/wiki/Israeliteshttp://en.wikipedia.org/wiki/Book_of_Exodushttp://en.wikipedia.org/wiki/Biblehttp://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Mudhttp://en.wikipedia.org/wiki/Straw -
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the mold cavity or onto the mold surface. The matrix material
experiences a melding event, after which the part shape is essentially set.
Depending upon the nature of the matrix material, this melding event
can occur in various ways such as chemical polymerization or
solidification from the melted state.
. Most commercially produced composites use a polymer matrix
material often called a resin solution. There are many different polymers
available depending upon the starting raw ingredients. There are several
broad categories, each with numerous variations. The most common are
known as polyester, vinyl ester,epoxy,phenolic,polyimide,polyamide,
polypropylene, PEEK, and others. The reinforcement materials are often
fibers but also commonly ground minerals. The various methodsdescribed below have been developed to reduce the resin content of the
final product, or the fibre content is increased. As a rule of thumb, lay up
results in a product containing 60% resin and 40% fibre, whereas
vacuum infusion gives a final product with 40% resin and 60% fibre
content. The strength of the product is greatly dependent on this ratio.
Fibre-reinforced plastic (FRP) (also fibre-reinforced polymer) are
composite materials made of a polymer matrix reinforced with fibres.
The fibers are usually fiberglass, carbon, or aramid, while the polymer isusually an epoxy, vinylester or polyester thermosetting plastic. FRPs are
commonly used in the aerospace, automotive, marine, and construction
industries.
Examples of polymers best suited for the process
Reinforcing
Material
Most Common Matrix
MaterialsProperties Improved
Glass FibersUP, EP, PA, PC, POM,
PP, PBT, VE
Strength, Elastic, heat
resistance
http://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Vinyl_esterhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Phenolichttp://en.wikipedia.org/wiki/Polyimidehttp://en.wikipedia.org/wiki/Polyamidehttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/PEEKhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Aramidhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Vinylesterhttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Thermosetting_plastichttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Vinylesterhttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Aramidhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Fiberglasshttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/PEEKhttp://en.wikipedia.org/wiki/Polypropylenehttp://en.wikipedia.org/wiki/Polyamidehttp://en.wikipedia.org/wiki/Polyimidehttp://en.wikipedia.org/wiki/Phenolichttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Vinyl_esterhttp://en.wikipedia.org/wiki/Polyester -
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Carbon and
Aramid FibersEP, UP, VE, PA Elasticity, Tensile Strength
Inorganic
Particulates
Semicrystalline
Thermoplastics, UP
Isotropic shrinkage,
abrasion, compression
strength
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UNIT II
PART A
1. Define co - polymerization.
2. What are plastics?3. Difference between thermosetting and thermoplastics. (any four)
4. Write notes on Epoxides.
5. Give any two properties of PC, Polyamide.
6. What is elastomer?
7. Define SBR (or) BUNA S. and explain the preparation of the same.
8. Define polymer. Give examples.
9. Define monomer. Give examples.
10.What is dead polymer?
11.What are engineering plastics?12.What is fluon? Mention its uses.
13.What is vulcanization of rubbers?
14.Mention some important uses of SBR.
15.What is the role of fillers in plastics?
16.Draw the structure of Bakelite.
17.What is the function of plasticizers in plastics?
18.Define degree of polymerization.
19.Define oligomers and high polymers.
20.How PVC is prepared?
PART B
1. Differences between addition and condensation polymerization?
2.Discuss the mechanism of addition (free radical) polymerization.
3.Write notes on vulcanization of rubber.
4. What is compounding of plastics? Give the names of various ingredients and
their function.5.Discuss the injunction moulding process with neat sketch.
Describe the preparation properties and uses of Bakelite.
6.How do you prepare the following polymers
Teflon 2) Nylon 6, 6 3) Polystyrene 4) Polyurethane
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7.Differentiate between thermoplastic and thermosetting resins.
8.Preparation, properties and uses of the following synthetic rubbers.
a) Buna S b) Butyl rubber
9.Explain compression moulding of plastics with a neat diagram.
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UNIT III SURFACE CHEMISTRY
AdsorptionTypesAdsorption of gases on solidsAdsorption
isothermsFreundlich
and Langmuir isothermsAdsorption of solids from solutionRole ofadsorption in
catalysis - Ion exchange adsorptionPollution abatement.
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Unit:3
Surface chemistry
Adsorption is the phenomenon of concentration of molecules of agas or liquid at a solid surface.
The adsorption of gas on a solid is sometimes called occlusion.
The substance which is held on the surface of the solid is called the
adsorbate.
The solid that takes up a gas or a solute from the solution is called
the adsorbent.
Absorption implies that a substance is uniformly distributed
throughout the body of the solid or liquid.
Adsorption is the surface phenomenon, but absorption is bulk
phenomenon.
Sorption is the process in which both adsorption and absorption
takes place simultaneously.
Adsorption:
The phenomenon of concentration of molecule of a
gas(or)liquid at a solid surface is called
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adsorpation .
Types of adsorption:
1.physical adsorption
2.chemical adsorption
DIFFERENCES BETWEEN PHYSISORPTION AND CHEMISORPTION
Physisorption chemisorption
It is caused by intermolecularvanderwaals forces(weak) It is caused by chemical bondformation
Heat of adsorption is low(0-
40k.cal/mole.
Heat of adsorption is high(40-
400k.cal/mole.
Adsorption is completely reversible Adsorption is irreversible
Adsorption decreases with increase
in temperature.
Adsorption increases with
temperature.
Multilayer adsorption occurs. Only monolayer adsorption occurs.
Equilibrium is established rapidly. But it requires time.
It is not specific in nature. But it highly specific in nature.
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CHARACTERISTICS OF ADSORPTION
1. spontaneous.
2. Always accompanied by evolution of heat.
3. Accompanied both by decrease in enthalpy and entropy of the
system.
4. Selective process.
5 .The rate of adsorption depends on temperature.
6 .Adsorption is a physical phenomenon, but accompanied by a
chemical change.
7 .It is specific, it depends on the nature of adsorbent and adsorbate.
Physical adsorption:
Physical adsorption is the one,in which the adsorbed molecules
are held on the surface of the adsorbent by the weak physical (or)
vanderwaals force of attraction.
Ex: Adsorption of H2(or)O2 on charcoal.
Chemical adsorption : (or) chemisorptions
Chemical adsorption is the one,in which adsorbed molecules are
held on the surface of adsorbent by chemical bonds(covalent bond
(or)ionic bond)
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Ex: Adsorption of H2 on NI
H2 molecule is first adsorbed by vanderwaals force and then
undergoes dissociation to hydrogen atom .H-atom chemisorbed on NI
Adsorption of gases on solid :
All solids adsorb gases to some measurable extent . The
magnitude of adsorption of gases by solids depand on the
following factors.
1.Naure of gases.
2.Nature and surface area of adsorbents.
3.pressure of gas
4.Temparature of gas
5.Activation of absorbentFactors influencing adsorption of gases on
solids
Nature of gases
Easily liquefiable gases like HCL,NH3 adsorbed more easily than
the permanent gases like H2,O2, etc.,
This is due to (i) Critical temperature (ii) Vander waals foreces.
Nature and surface area of adsorbent
The greater the surface area, larger pores on the adsorbent
larger is the adsorption.eg.Charcoal and Silica gel.
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Heats (or) Enthalpy of adsorption
The energy liberated when 1 gm mole of a gas is adsorbed on
the solid surface. In physical adsorption it is small due to weak vander
waa,s forces, in chemical adsorption it is large due to the formation ofchemical bonds.
Reversible character
It is a reversible process. The gas adsorbed on a solid can be
removes under reverse conditions of temperature and pressure.
Chemical adsorption is not a reversible process, because a
surface compound is formed.
Effect of pressure
Since dynamic equilibrium exists between the adsorbed gas and
the gas in contact with the solid, increases of pressure increases
adsorption and decrease of pressure causes desorption.
Effect of temperature
Physical adsorption:It occurs rapidly at lower temperature and
decreases with increase in temperature.
Chemical adsorption: It increases with increase in temperature
and then decreases.
Vander waals forces:
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Easily liquefiable gases posses greater vander waals forces
than permanent gases
Thickness of adsorbed layer of gas
In physisorption multimolecular thick layer is formed, in
chemisorption one molecule thick layer is formed.
Effect of activation of adsorbent
Activation leads to increase in the surface.
(1)Creation of rough surface
(a) by mechanical rubbing,
(b) by subjecting to some chemical reactions on the solid
adsorbent.
(2)Increasing effective area of the surface
(a) by sub dividing the solid adsorbent into fine particles.(b) by heating of solid adsorbent in superheated steam now
its pores are opened and
adsorption increases.
ADSOPTION OF SOLUTES FROM SOLUTIONS
An adsorbent adsorbs substances(solutes) from the solution in two
ways.
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1.Solid substances adsorb dissolves substances from solutions.
Eg. Activated charcoal adsorbs coloring matter present in sugar
solution.
2.An adsorbent also adsorbs certain substance from the solution in
preference to other substances.
Eg. Charcoal adsorbs non-electrolytes more readily than electrolytes
from a solution.
FACTORS INFLUENCING ADSORPTION OF SOLUTES FROM
SOLUTIONS
1.Effect of temperature and concentration
(a)Negative adsorption
2.Effect of surface areaSurface area of the adsorbent increases, adsorption increases.
3.The nature of the solute adsorbed
The extent of adsorption is usually greater, when the
molecular weight of the solute is high.
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ADSORPTION ISOTHERMS
Definition: Adsorption isotherm is a relationship (or a graph) between
magnitude of adsorption with pressure at constant temperature
FREUNDLICHS ADSORPTION ISOTHERM
The relationship between the magnitude of adsorption (x/m) and
pressure (P) can be expressed mathematically by an empirical equation
known as Freundlich adsorption isotherm.
I.e., x/m = KP1/n
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DERIVATION OF FREUNDLICHS ADSORPTION ISOTHERM
This equation may be derived from the result observed from the above
graph. Thus,
(i) At low pressure: Adsorption increases with pressure
x/m P (or) x/m=KP
(ii)At high pressure: Adsorption is almost constant
x/m = constant (or) x/m = K
(iii)At intermediate (normal) pressure: Adsorption depends on 0 to 1
power of pressure (ie., fraction a power of pressure)
x/m P1/n
(or) x/m = KP1/n .(1)
where, n= whole number.
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(1) This eqn(1)is called Freundlichs adsorption isotherm.
Taking logarithm on both sides, the above equation becomes
log x/m=log K + 1/nlog P
On plotting logx/m Vs logP, a straight line is obtained with a slope of
1/n and intercept log K.
DISADVANTAGES / LIMITATIONS OF FREUNDLICHS
ADSORPTION ISOTHERM
1.Freundlich equation is purely empirical and has no theoretical basis.
2.The equation is valid only upto a certain pressure and invalid at
higher pressure.
3.The constants K and n are not temperature independents, they vary
with temperature.
4.Freundlichs adsorption isotherm fails, when the concentration of
adsorbate is very high.
LANGMUIRS ADSORPTION ISOTHERM
Langmuir derived an equation based on some theoretical
considerations.
The postulates (or) assumptions of langmuir,s theory are
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1.Valencies at the surface of adsorbent are not fully satisfied.
2.The adsorbed gas layer on the solid surface is only one moleculethick.
3.The surface of the solid is homogeneous, so the adsorbed layer is
uniform all over the adsorbent.
4.There is no interaction between the adjacent adsorbed molecules.
5.The adsorbed gas molecules do not move around on the surface.
DERIVATION OF LANGMUIR ISOTHERM
According to Langmuir,s assumptions, when the gas molecules strike
a sold surface, some of the molecules are adsorbed and some of these
are desorbed. Thereby dynamic equilibrium is established betweenadsorption and desorption. If A is gas molecule and M is surface then,
ka
A(g) + M(surface) AM
kd
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Let,
Fraction of the total surface covered by the adsorbed
molecule =
Fraction of uncovered are (vacant area) = (1- )
The rate of desorption is proportional to number of adsorbed
molecules = Rd=kd
where, kd= Rate constant for desorption.
Thus, the rate of adsorption is proportional to available
uncovered area=Ra=ka(1- )P
Where, ka= Rate constant for adsorption.
At euilibrium
Rate of desorption Rate of adsorption
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kd =ka(1- )P
=kaP-ka P
kd +ka P=kaP
(kd+kaP)=kaP
= kaP ------------------------(1)
(kd=kaP)
Dividing the equation (1) by kd, it becomes
= (ka/kd)P
1+ (ka/kd)P
= KP .(2)
1+KP
where, ka/kd=K= equilibrium constant, called adsorption coefficient.
But, the amount of gas adsorbed per gram of the adsorbent, x, is
proportional to
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x (3)
on comparing equation (2) and (3), it becomes
x KP
1+KP
x = K KP (4)
1+KP
where, K = New constant.
The equation (4) gives the relation between the amount of gas
adsorbed to the pressure of the gas at constant temperature is known
as Langmuir Adsorption isotherm.
The above equation (4) may be re-written as
1+KP = KKP
x
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1 + KP = P
KK KK x
1 + K P = P
KK KK x
The equation (5) is similar to an equation for a straight line (ie.,
y=c+mx). If the graph is plotted between p/x Vs P, we should get a
straight line with slope K and the intercept1/kk
This equation is found valid in all cases.
Case (I): At low pressure : If the pressure (P) is very low K P term
is negligible, kk
i.e., 1 K P
KK KK
Hence equation (5) becomes
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1 = P
KK x (or) x = PKK (6)
ie., amount of adsorption per unit weight of adsorbent is directly
proportional to the P at high 1 term is negligible,
KK
K P 1
KK KK
Hence equation (5) becomes
K P = P
KK x (or) x = K (constant)
(or) x = K P0 ..(7)
ie., extent of adsorption is independent of pressure of the gas, because
the surface becomes completely covered at high pressure.
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Case (iii) At normal pressure: At normal (intermediate) pressure the
equation (7) becomes
X=KPn (8)
Where, n lies between 0 and 1.
Equation (8) is Freundlichs adsorption isotherm.
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MERIT AND DEMERIT
Langmuir adsorption isotherm holds good at lower pressure but fails at
high pressure.
APPLICATIONS OF ADSORPTION
1.Activated Charcoal
(a)Gas-Masks - absorb toxic gases.
(b) Remove coloring matter from the sugar solution and the
decoloration in vinegar
2.Silica and alumina gels
These are used as adsorbent for removing moisture and for
controlling humidities of room.
3. Ion exchange resins
Softening of hard water can be done based on the principle of
competing adsorption using ion-
exchange resins.
4. Chromatographic analysis
Selective adsorption by alumina, magnesia, etc., can be used
for separating different pigments and
also mixtures of small quantities of organic substances with the
help of adsorption chromatography.
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4.Measurement of surface area
5.Surface area of powders and rough surfaces can be measured using
adsorption measurements.
ROLE OF ADSORBENT IN CATALYTIC REACTIONS (OR) ADSORPTION
(OR) CONTACTTHEORY
1.Action of heterogeneous catalyst:
Hydrogenation of ethylene using Ni catalyst.
Step :1
Adsorption of reactant molecule
Step:2
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Step:iii Decomposition of activated complex
Step iv: Desorption of product:
Finely divided state of catalyst is more efficient.
.
Free valencies=12
Desorption of products
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The products are desorbed (or) released from the surface. They are
stable.
2.Finely divided state of catalyst is more efficient
Fineness of the catalyst increase, the free surface area gets
increases, thereby free valencies increases.
3.Enhanced activity of a rough surfaced catalyst
It possess Cracks, Peaks, Corners etc., and consequently
have larger number of active centers. These active centers increase the
rate of reaction.
4.Action of promoters
Promoters are defined as the substances, which increase the activity of
a catalyst.
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(i) Promoters change the lattice spacing
(ii) Promoters increase the peaks and cracks
5.Action of catalytic poisons
Catalytic poison is defined as a substance which destroys the activity of
the catalyst to accelerate a reaction.This process is called catalytic
poisoning.
Number of free valencies (or) active centres of catalysts are
reduced by the preferential adsorption of the poison. So rate of
reaction decreases.
6.Specific action of the catalyst
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The adsorption depends on the nature of both the adsorbent
(catalyst) and the adsorbate (reactants). So, different catalysts cannot
possess the same affinity for the same reactants. Thus, the action of
the catalyst is specific.
ACTIVATED CARBON IN POLLUTION ABATEMENT OF AIR AND WASTE
WATER
Activated carbon is the most commonly used adsorbent because it has
a large surface area per unit weight (or) unit volume of solid.
Scope of the study
1.Preparation and properties of activated carbon.
2.Use of granular and powdered activated carbon.
3.Regeneration of activated carbon.
Production of Activated Carbons
Step I: Production of Char
The char is produced by heating the materials like coconut, wood,
coal, petroleum residues to a red heat in a retort to remove the
hydrocarbons but with an insufficient supply of air to sustaincombustion.
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Step II: Activationof Char Particles
The char particles are then activated by exposure to an oxidizing gas
at a high temperature. The gas
Creates a porous structure and large internal surface area in the char
due to the removal of adsorbed hydrocarbons and some of the carbon.
Classification of Activated Carbon
Based on size and different adsorption capacities-two main classes.
1.Granular Activated Carbons(GAC)
These carbons have a diameter of greater than 0.1 mm and are
generally used for the adsorption of gases and vapours.
2.Powdered Activated Carbons(PAC)
These carbons have a diameter of less than 200mesh and are generally
used in purification of liquids.
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Properties of Activated Carbon
The properties of Ac are governed not only by the nature of raw
materials but also by the method of activation used. Property of AC ishighly helpful in specifying the carbon for a specific applications.
Eg.1.Decolorizing activated carbon:
It is usually employed as powders.Generally raw material for this
type have a weak structure.
Eg. Saw dust and lignite yield carbon of this kind.
2.Vapour adsorbent carbon: It is used in the form of hard
granules.
Eg. Coconut shells, fruit pits, briquette coal yield carbon of this kind.
Adsorptive Capacity: It is used to find out the effectiveness of the
carbon in removing desired constituents such as COD, colour,
phenol,etc., from the waste water.
Phenol number: It is used the find out the ability of AC to remove
taste and odour compounds.
Iodine number: It is used to find out the ability of AC to adsorb low-
molecular weight substances.
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TREATMENT OF POLLUTED WATER AND AIR
1.Using Granular Activated Carbon (GAC)
A fixed bed column is often used for contacting polluted water or air
with GAC.It can be operated singly, in series or in parallel.Among the
various type two are important.
1.Down flow carbon contactors.
2.Upflow carbon contactors.
(A) Down flow Carbon Contactors
It usually consist of two (or) three columns operated in series (or) in
parallel.
The water or air is applied to the top of the column and withdrawn
at the bottom. The AC is held in place with an under drain system at the
bottom of the column. Provision for back washing and surface washing
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is usually necessary to limit the headless build up due to the removal of
particle material with the carbon column.
Advantage
Adsorption of organic materials and filtration of suspended solids are
accompanied in a single step.
Disadvantages
Down flow filters may require more frequent back washing because
of the accumulation of suspended materials on the surface of the
contactor.
Plugging of carbon pores may require premature removal of the
carbon for regeneration, thereby decreasing the useful life of the
carbon.
(b)Upflow Carbon Contactors
In the upflow columns, the polluted water or air moves upward from
the base of the column .
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Advantage:
As the carbon adsorbs organic materials, the apparent density of
the carbon particles increases and encourages migration of the heavier
or spent carbon downward.
Disadvantage
upflow columns may have more carbon fines in the effluent than
downflow columns, because upflow tends to expand, not compress, the
carbon.
Bed expansion allows the fines to escape through passage ways
created by the expanded bed.
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2.Using Powdered Activated Carbon (PAC)
In this method PAC is added directly to the effluent coming out from
the various biological treatment processes. In the case of biological-treatment plant effluent, PAC is added to the effluent in a contacting
basin. After some time, the carbon is allowed to settle at the bottom of
the tank, and the treated water is then removed from the tank.
Since carbon is very fine, a coagulant such as polyelectrolyte may be
added to aid the removal of the carbon particles or filtration throughgranular medium filters may be required.
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Regeneration of Activated Carbon
Thermal methods are widely and effectively used.
(i)Granular carbon It can be regenerated easily in a furnace by heatingin the presence of limited amount of water vapour, flue gas and
oxygen. Some of the carbon (5 to 10%) is destroyed in the regeneration
process and must be replaced with new carbon.
(ii) Powdered carbon
This methodology is not well-defined. The use of powdered AC,
produced from recycled solid wastes, makes no need of regeneratingthe spent carbon.
Applications of Activated Carbon
There is no particular AC that is effective for all purposes.
*In odour controi
As a decolourantIn solution purification
In gas masks-to adsorb poisoning gases.
In Air Conditioning-to control odour.
In industrial recovery
Activated carbon adsorbs practically any organic solvent at
about 35 oC and releases it when heated to 120oC or higher for solvent
recovery.
*In cigarette filters-Specially impregnated are used.
In the removal of organic and inorganic compounds
It is generally used for the removal of the refractory organic
compounds as well as residual
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amounts of inorganic compounds such as nitrogen, `sulfides and
heavy metals.
In odour control :
Activated carbon adsorbets are commonly used for odour
control . activated carbon has different rate of adsorption for
different substances.
In soln purification
Activated carbon is also used in cleaning sugar soln.
In gas masks
The vapour adsorbent type of activated carbon is used in gas
masks.
Activated carbon is also effective in adsorbing organic molecules
even from humid gas and stream.
Role of adsorbents in ion exchange adsorption :
Ion exchange adsorption is defined as the process of
releasing the ion and adsorbing another like ion.
Classification of ionexchangers:
1.cation exchanger
2.Anion exchanger
Softening(or)conditioning method:
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The process of removing hardness producing salts from
water is known as softening(or)conditioning of water.
This method can be done in 2 methods
1.External conditioning
2.Internal conditioning
External conditioning:
Ion exchange (or)demineralization process.
Cation exchanger:
Resins containing acdic functional groups (COOH, SO3H ) are
capable of exchanging their H+ Ions with other cations .cation
exchange resins is represented as
1.sulphonated coals.
2.sulphonated polystyrene RSO3H
Anion exchanger:
Resins contains basi functional groups (NH2,OH) are capable of
exchange their anions with other anions .anion exchange resin
represented as R(OH)2
EX:1.cross linked quaternary ammonium salts.
RH2+CaCl2RCa2HCl
RH2+mgso4RmgH2SO4
RHNaClRNaHCl
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Regeneration:
RCa2HClRH2+CaCL2
RNaHClRHNaCl
RCl22NaOHR(OH)2+2NaCl
Carbonate conditioning: scale formation can be avoided by adding
Na2CO3 to the boiler water.
CaSO4+Na2CO3CaCO3+Na2SO4
Phosphate conditioning: scale formation can be avoided by addingsodium phosphate.
3CaSO4+2Na3po4Ca3(po4)2
Trisodiumphospate Na3po4(Weaklyalkaline) used for too acidic water.
Disodium hydrogen phosphate-Na2HPO4(weakly alkaline) used for alka
weakly acdic water.
Sodium dihydrogen phosphate-NaH2PO4(acidic) used for alkaline
water.
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Calogen conditioning
Calogen is sodium hexa meta phosphateNa2[Na4(PO3)6]
2Caso4+Na2[Na4(po3)6+Na2[Ca2(PO3)6]+2Na2SO4
The complex Na2[Na4(po3)6] is soluble in water and ther is no problem
of sludge disposal. So calogen conditioning is better than phosphate
conditioning.
Zeolite process:
Hard water contains Ca2
+&Mg2
+ ions this ions form hard soap(in soluble)with soap which does not produce lather with soap soln.
Hard water is softened by passing it through a column packed with
sodium cation exchange resin (called sodium zeolite )
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Na2Ze+Ca2CaZe2Na
Synthetic zeolite is represented by Na2Ze. The sodium ions which are
loosely held in Na2Ze are replaced by Ca2+
and Mg2+
ions present in the
water.
Process:
Sodium ions with Ca2+
and Mg2+
ions present in the water to form Ca
and Mg ions present in the water.
Ca(HCO3)+Na2Ze CaZe+2NaHCO3
Mg (HCO3)+Na2Ze MgZe2NaHCO3
CaSO4+ Na2Ze CaZeNa2SO4
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Mg SO4+ Na2Ze Mg ZeNa2SO4
CaCl2 +Na2Ze CaZe2NaCl
Mg Cl2 +Na2Ze Mg Ze+2NaCl
Regeneration:
CaZe+2Na+Cl
-Na2Ze
1.water softening (demineralization process)
The hard water first passed through a cation exchange
column .which adsorbs all the cations like Ca
2+
,Mg
2+
RH2+CaCl2RCa2HCl
RH2 +Mgso4RMg H2SO4
Regeneration:
RCa 2HClRH2+ CaCl2
RNa +HCl RH NaCl
CaZe+ 2Na+
Cl- Na2Ze +CaCl2
Electrical demineralization of water
Ion exchange resins supported on paper or fibre can be used
as membranes called ion selective membranes.
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Process: the cation selective membrane permits only cations
but not anions .anion selective membrane permits only anion
but not cation.
Medical uses:
Excess sodium salts from the body fluids can be removed by
giving a patient a suitable ion exchanger to eat.
Weakly basic anion exchanger are used to remove excess
acid (or)acidity in the stomach.
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Unit-III
PART A
1. Define adsorption and adsorbate.
2. What is a chemisorption. Give example?
3. What is physisorption? Give example.
4. Mention some important characteristics of adsorption.
5. How will you increase the activity of an adsorbent?
6. Explain the effect of temperature on adsorption.
7. What is Freundlich adsorption isotherm?
8. Explain the limitation of Freundlich adsorption isotherm.
9. Write the mathematical expression of Langmuir isotherm.
10. What is the demerit of Langmuir adsorption isotherm?
11. What are promoters?
12. What is catalytic poisoning?
13. What is the effect of temperature and pressure on the adsorption of hydrogengas on charcoal?
14. How is arsenic poisoning removed from the body?
15. Define ion exchange adsorption.
16. How is evaporation of water in lake is minismised?
17. What is the role of adsorbent in catalysis?
18. Define adsorption isotherm.
19. Mention any three factors of affecting adsorption of gases on solids.
20. (a)Give any two applications of adsorption.
(b)What is critical temperature?
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(c)Define Enthalpy of adsorption.
(d)What is effect of temperature of gas in adsorption?
(e)Define Freundlich Adsorption isotherm.
(f) Mention any four postulates of Langmuirs adsorption isotherm
PART B
Explain the role of adsorbents in catalytic adsorption.
1. Derive the Langmuir adsorption isotherm and interpret the results.
2Distinguish between physisorption and chemisorption.
3. Write a note on adsorption of solute from solution.
4. Write a note on application of adsorption.
5. What are the factors affecting gases on solids in adsorption.
6. State and derive the expression for Freundlich adsorption isotherm.
7. Explain treatment of polluted water by using powdered activated carbon.
8. Describes Zeolite process of Adsorption.
9. What are the characteristics of adsorption?
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UNIT IV NON CONVENTIONAL ENERGY SOURCES AND
STORAGE DEVICES
Nuclear energyfission and fusion reactionsLight water nuclear
reactor for powergeneration (Block diagram only)Breeder reactorSolar energy
conversionSolar
cellsWind energyFuel cellsHydrogenOxygen fuel cell
BatteriesAlkaline
batteriesLead acid storage batteryNickelCadmium and Lithium
batteries.
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UNIT -4
NON CONVENTIONAL ENERGY SOURCES AND STORAGE
DEVICES
Nuclear fission: It is the nuclear reaction in which heavy
isotopes are split into lighter nuclei on bombardment by
neutrons. Fission reaction of U235
is given below
92U
235
+0n1 36Kr
92
+ 56Ba
141
+ 3 0n
1
+ energy
(Structure of fission reaction)
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Nuclear fusion: Process of combination of lighter nuclei
into heavier nucles with simultaneous liberation of large
amount of energy. (e.g) solar system
1H2
+ 1H2 2 He
4+ Energy
Nuclear fusion reaction occurs in sun.
Differences between fission and fusion reaction
S.No Nuclear fission Nuclear fusion
1 It is a process of breaking a
heavier nucleous.
It is a process of
combination of lighter
nuclei.
2 It emits radioactive rays It does not emit any kind
of radioactive rays3 The mass number and
atomic number of new
elements are lower than
The mass number and
atomic number of
product is higher than
that of starting elements
4 It occurs at ordinary
temperature
It occurs at high
temperature
5 It gives rise to chainreaction
It does not give rise tochain reaction
6 It emits neutrons It emits positrons
7 It can be controlled It canot be controlled
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Nuclear Energy
The enormous amount of energy released during the
nuclear fission is due to the loss in some mass.
During nuclear fission, the sum of the masses of the
products formed is slightly less than the sum of masses
of target species and bombarding neutron.
The loss in mass gets converted into energy according to
Einsteins equation
E = mc2
Where,
C = velocity
m= mass lose
E= energy
Light water nuclear power plant
Definition
Light water nuclear power plant is one in which
U235 feel rods are submerged in water. Here thewater acts as coolant and moderator.
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The fission reaction is controlled by inserting or
removing the control rods of B10
automatically
from the spaces I between the fuel rods
The heat emitted by U235
in the fuel core isabsorbed by the coolant
Heat is transferred to sea water and then
converted into steam.
The steam then drives the turbines, generating
electricity.
(Str of light water nuclear power plant)
BREEDER REACTOR:
A breeder reactor is a nuclear reactor that generates
new fissile or fissionable material at a greater rate than it
consumes such material. These reactors were initially (1940s
and 1960s) considered appealing due to their superior fuel
economy; a normal reactor is able to consume less than 1% of
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the natural uranium that begins the fuel cycle, whereas a breeder
can utilize a much greater percentage of the initial fissionable
material, and with re-processing, can use almost all of the initial
fissionable material. Breeders can be designed to utilize thorium,which is more abundant than uranium. Currently, there is
renewed interest in breeders because they would consume less
natural uranium (less than 3% compared to conventional light-
water reactors), and generate less waste, for equal amounts of
energy, by converting non-fissile isotopes of uranium into
nuclear fuel.
Production of fissile material in a reactor occurs byneutron irradiation of fertile material, particularly uranium-238
and thorium-232. In a breeder reactor, these materials are
deliberately provided, either in the fuel or in a breeder blanket
surrounding the core, or most commonly in both. Production of
fissile material takes place to some extent in the fuel of all
current commercial nuclear power reactors. Towards the end of
its life, a uranium (not MOX, just uranium) PWR fuel element is
producing more power from the fissioning of plutonium than
from the remaining uranium-235. Historically, in order to be
called a breeder, a reactor must be specifically designed to
create more fissile material than it consumes.
Photo galvanic cell or Solar cell
Definition
Photogalvanic cell is the one , which converts the solar
energy ( Energy received from the sun) into electrical
energy.
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Principle
Solar cells consists of a p-type semiconductor(si with B)and n-type semiconductor(si with P)
When solar rays fall on the top layer of p-type
semiconductor, the electrons from the valence band get
promoted to the conduction band and cross the p-n
junction into n-type semiconductor.
Thereby potential difference between two layers is
created, which causes flow of electrons
(Solar cell)
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Uses:
Used in calculators, electronic watches, street lights, water
pumps to run radios and TVs.
Solar Battery
Working
When large number of solar cells are connected in series it
form a solar battery.
Solar battry produce more electricity which is enough to
run water pump, street light etc.,Uses:
They are used in remote areas where conventional
electricity supply is a problem.
Solar light
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WIND ENERGY
Moving air is called wind. Energy recovered from the forces of
wind is called wind energy.
Wind power is the conversion of wind energy into a
useful form, such as electricity, using wind turbines. At the end
of 2008, worldwide nameplate capacity of wind-powered
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generators was 121.2 gigawatts (GW). Wind power produces
about 1.5% of worldwide electricity use, and is growing rapidly,
having doubled in the three years between 2005 and 2008.
Large-scale wind farms are typically connected to the local
electric power transmission network; smaller turbines are used
to provide electricity to isolated locations. Utility companies
increasingly buy back surplus electricity produced by small
domestic turbines. Wind energy as a power source is attractive
as an alternative to fossil fuels, because it is plentiful,
renewable, widely distributed, clean, and produces no
greenhouse gas emissions; however, the construction of wind
farms (as with other forms of power generation) is not
universally welcomed due to their visual impact and other
effects on the environment.
Wind power is non-dispatchable, meaning that foreconomic operation all of the available output must be taken
when it is available, and other resources, such as hydropower,
and standard load management techniques must be used to
match supply with demand. The intermittency of wind seldom
creates problems when using wind power to supply a low
proportion of total demand. Where wind is to be used for a
moderate fraction of demand, additional costs for compensation
of intermittency are considered to be modest. Studies of a paneuropean power grid, show that wind can be used to meet eg
70% of load, over a wide area of interconnected grids, and then
the costs of electricity delivered into the consuming country are
comparable to present day power cost.
http://en.wikipedia.org/wiki/Gigawatthttp://en.wikipedia.org/wiki/Wind_farmshttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Net_meteringhttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Renewable_energyhttp://en.wikipedia.org/wiki/Greenhouse_gas_emissionshttp://en.wikipedia.org/wiki/Environmental_effects_of_wind_powerhttp://en.wikipedia.org/wiki/Hydropowerhttp://en.wikipedia.org/wiki/Load_managementhttp://en.wikipedia.org/wiki/Intermittent_power_sourceshttp://en.wikipedia.org/wiki/Intermittent_power_sourceshttp://en.wikipedia.org/wiki/Load_managementhttp://en.wikipedia.org/wiki/Hydropowerhttp://en.wikipedia.org/wiki/Environmental_effects_of_wind_powerhttp://en.wikipedia.org/wiki/Greenhouse_gas_emissionshttp://en.wikipedia.org/wiki/Renewable_energyhttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Net_meteringhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Wind_farmshttp://en.wikipedia.org/wiki/Gigawatt -
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FUEL CELLS:
A fuel cell is an electrochemical conversion
device. It produces electricity from fuel (on the anode side) and
an oxidant (on the cathode side), which react in the presence of
an electrolyte. The reactants flow into the cell, and the reaction
products flow out of it, while the electrolyte remains within it.Fuel cells can operate virtually continuously as long as the
necessary flows are maintained.
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Fuel cells are different from electrochemical cell
batteries in that they consume reactant from an external source,
which must be replenisheda thermodynamically open system.
By contrast, batteries store electrical energy chemically andhence represent a thermodynamically closed system.
Many combinations of fuels and oxidants are
possible. A hydrogen fuel cell uses hydrogen as its fuel and
oxygen (usually from air) as its oxidant. Other fuels include
hydrocarbons and alcohols. Other oxidants include chlorine and
chlorine dioxide.
http://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Thermodynamic_systemhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Alcoholhttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Chlorine_dioxidehttp://en.wikipedia.org/wiki/Chlorine_dioxidehttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Alcoholhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Thermodynamic_systemhttp://en.wikipedia.org/wiki/Battery_(electricity) -
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(HydrogenOxygen fuel cell)
ENERGY STORAGE DEVICES
Battery:
It is an arrangement of several electrochemical cells
connected in series that can be used as a source of direct
electric current.
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Secondary battery or secondary cells
In these cells, the electrode reactions can be reversed by
passing an external energy.
They can be recharged by passing electric current.
They are called storage cells or accumulators.
Ex: Lead acid storage cell, Nickel- cadmium cell.
Alkaline Battery
Here the powdered zinc is mixed with KOH and MnO2 to
get a gel
A Carbon rod acts as cathode. IT is immersed in KOHThe outside cylindrical body is made up of zinc
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Cell reactions
At anode : Zn (s) + 2OH- Zn(OH)2 + 2e-
At cathode: 2MnO2 + H2O(l) + 2e- 2OH- +Mn2O3
Overall reaction:
Zn (s) + 2MnO2 + H2O(l) Zn(OH)2 + Mn2O3
Uses: It is used in calculators, watches etc.,
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Lead storage cell
Description:
It consists of number of voltaic cells connected in seriesPb is anode and PbO2 is cathode
Number of Pb plates and PbO2 plates are connected in
parallel.
Plates are separated from adjacent ones by insulators
like rubber or glass fiber.
This arrangement is immersed in dil. H2SO4
(Lead acid Battery)
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Cell reactions
At anode : Pb (s) + SO42- PbSO4 (s) + 2e-
At cathode: PbO2(s) + SO42-
+ 4H+
+ 2e- PbSO4
+2H2O
Overall reaction:
Pb (s) + PbO2(s) + 2H2SO4 PbSO4 + H2O +
energy
Uses:
It is used to supply current mainly in automobiles
such as cars. Buses, trucks, etc.,
It is also used in gas engine ignition, telephone
exchanges, hospitals, power stations.
Nickel Cadmium Battery
Description
It consists of a cadmium anode.
a metal grid containing a paste of NiO2 acting as a cathode.
KOH is electrolyte
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Ni-Cd battery
Cell reactions
At anode: Cd(s) + 2OH- Cd(OH)2(s) + 2e-
At cathode: NiO2 + 2H2O(l) + 2e- 2OH- +Ni(OH)2 (s) +
energy
Overall reaction:
Cd(s) + NiO2 + 2H2O(l) Cd(OH)2(s) + Ni(OH)2 (s) + energy
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Uses:
It is used in calculators. Electronic flash units, transistors
and cordless appliances.
Lithium Battery
Description
It consists of a lithium anode and a TiS2 cathode.
A solid electrolyte generally a polymer is packed in
between the electrodes.
The electrolyte permits the passage of ions but not
electrons.
Cell reactions
At anode: Li(s) Li+
+ e-
At cathode: TiS2 + e- TiS2-
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Lithium Sulphur Battery
Description
It consists of a lithium anode and a graphite cathode.
A solid electrolyte generally -Alumina is packed in
between the electrodes.
Here sulphur is electron acceptor
Cell reactions
At anode: Li(s) Li+
+ e-
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At cathode: S + 2e- S2-
Overall reaction:
2Li(s) + S 2Li+ + S2-
The sulphide ions, formed, react with elemental sulphur to
form the polysulphide ion.
Uses
It is used in electric cars
Li-S battery has light weight unlike the lead acid battery.It possesses a high energy density.
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Unit 4
Part-A
1. Define nuclear fission with example.
2. Mention a few important characteristics of nuclear fission.
3. What is nuclear fusion reaction? G