E.G.S. PILLAY ENGINEERING COLLEGE (An Autonomous Institution, Affiliated to Anna University, Chennai) Nagore Post, Nagapattinam – 611 002, Tamilnadu. Rev.0 COE/2017/QB 1701CH103 WATER VTECHNOLOGY AND GREEN CHEMISTRY Academic Year : 2017-2018 Question Bank Programme : B.E – CIVIL Year / Semester : I / I Course Coordinator: Course Objectives Course Outcomes: 1. Imparting knowledge on the principles of water characterization, treatment methods and industrial applications 2. Understanding the principles and application of electrochemistry and corrosion science. 3. Basic information and application of polymer chemistry, nanotechnology and analytical techniques On completion of the course, students will be able to CO1. Understand the chemistry of water and its industrial & domestic application (K2). CO2. Utilization of electrochemistry principles in corrosion control and industrial application (K2) CO3. Differentiate the polymers and materials used in day to day life based on its source, properties and applications(K2) CO4. Identify the applications of nanotechnology and analytical methods for the estimation of elements (K2) PART – A ( 2 Mark Questions With Key) S.No Questions Mark COs BTL UNIT I- WATER TECHNOLOGY 1 Define the term hardness of water CO1 (K1) Hardness is the property or characteristics of water , Which does not produce lather with soap. 2 CO1 (K1) 2 Compare temporary and permanent hardness in water. CO1 (K2) Temporary hardness It is due to carbonates and bicarbonates of calcium and magnesium. It can be removed by boiling the water. Permanent hardness It is due to chlorides and sulphates of calcium and magnesium. . It can not be removed by boiling the water. 2 CO1 3 Calgon conditioning is advantageous over phosphate conditioning- Why. CO1 (K2) Calgon is Sodium hexa meta phosphate Na 2 (Na 4 (PO 3 ) 6 ). 2. 1 CO1
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E.G.S. PILLAY ENGINEERING COLLEGE (An Autonomous Institution, Affiliated to Anna University, Chennai)
Nagore Post, Nagapattinam – 611 002, Tamilnadu.
Rev.0 COE/2017/QB
1701CH103 WATER VTECHNOLOGY AND GREEN CHEMISTRY
Academic Year : 2017-2018 Question Bank
Programme : B.E – CIVIL
Year / Semester : I / I Course Coordinator:
Course Objectives
Course Outcomes:
1. Imparting knowledge on the principles of water characterization, treatment methods and industrial applications
2. Understanding the principles and application of electrochemistry and corrosion science.
3. Basic information and application of polymer chemistry, nanotechnology and analytical techniques
On completion of the course, students will be able to
CO1. Understand the chemistry of water and its industrial &
domestic application (K2).
CO2. Utilization of electrochemistry principles in corrosion control and industrial application (K2)
CO3. Differentiate the polymers and materials used in day to
day life based on its source, properties and applications(K2)
CO4. Identify the applications of nanotechnology and analytical methods for the estimation of elements (K2)
PART – A ( 2 Mark Questions With Key)
S.No Questions Mark COs BTL
UNIT I- WATER TECHNOLOGY
1 Define the term hardness of water
CO1 (K1)
Hardness is the property or characteristics of water , Which does not
produce lather with soap. 2
CO1 (K1)
2 Compare temporary and permanent hardness in water.
CO1 (K2)
Temporary hardness It is due to carbonates and bicarbonates of calcium and
magnesium.
It can be removed by boiling the water.
Permanent hardness
It is due to chlorides and sulphates of calcium and
magnesium.
. It can not be removed by boiling the water.
2
CO1
3 Calgon conditioning is advantageous over phosphate conditioning- Why.
CO1 (K2)
Calgon is Sodium hexa meta phosphate Na2 (Na4 (PO3)6). 2. 1
CO1
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This substance interacts with calcium ions foming a highly soluble
complex and thus 3. the precipitation of scale forming salt.
Scale formation can be avoided by adding sodium phosphate. It is used high pressure boilers.The phosphate react with Ca2+ and Mg2+ salts to give soft sludges Ca and Mg phosphates.
3CaSO4 +2Na3PO4 Ca3 (PO4)2 +3Na2SO4
2 CO1
5 What are the disadvantages of scale formation?
CO1 (K1)
Scale act as thermal insulators. It decreases the efficiency of boiler. Any crack developed on the scale, leads to explosion.
1
1
CO1
6 What are boiler compounds? Give two examples.
CO1 (K1)
Scale forming substances can be removed by adding chemicalsdirectly to the boiler. These chemicals are called boiler compounds.Examples: Sodium carbonate and sodium phosphate
i) CaSO4 +Na2CO3 CaCO3 +Na2SO4
(ii)3CaSO4 +2Na3PO4 Ca3 (PO4)2 +3Na2SO4
2 CO1
7 Distinguish between hard and soft water
CO1 (K2)
Hard water:
(i) Hard water does not produce lather with soap solution.
(ii)It gives wine red color with EBT indicator Soft water:
(i)Soft water produces very good lather with soap solution. (ii)It does not give color with EBT indicator.
1
1
CO1
8 List two disadwantages of using hardwater in boilers.
CO1 (K1)
(i).Formation of deposits (Scale and sludge) in boilers. 2 CO1
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(ii).Priming and foaming (carry over).
(iii). Caustic embrittlement.
(iv).Boiler corrosion.
9 What is meant by priming and foaming?
CO1 (K1)
Priming is the process of production of wet steam. Foaming is the formation of stable bubbles above the surface of water.
2 CO1
10 Name the gases dissolved in water that cause corrosion?
CO1 (K1)
(i).Dissolved oxygen(DO)
(ii). Dissolved Carbon dioxide(CO2)
2 CO1
11 Distinguish between hard water and soft water.
CO1 (K2)
Hard water Soft water
(i)Hard water does not produce lather with
soap solution.
(i)Soft water produces very good
lather with soap solution.
(ii)It give wine red colour with EBT
indicator.
(ii)It does not give colour with
EBT.
1
1
CO1
12 What is meant by softening or conditioning of water? How is it carried out?
CO1 (K1)
The process of removing hardness producing salts from water is known as
softening (or) conditioning of water.
Softening of water can be done in two methods
1. External conditioning.
2. Internal conditioning.
2 CO1
13 What is blow-down operation?
CO1 (K1)
Blow-down operation is a process of removing a portion of concentrated
water by fresh water frequently from the boiler during steam production.
2 CO1
14 What are the requirements of boiler feed water?
CO1 (K1)
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2 CO1
15 Soft water is not DM water whereas DM water is soft water- Justify
CO1 (K2)
The soft water, produced by lime-soda and zeolite processes, does not
contain hardness producing Ca2+
and Mg2+
ions, but it will contain other ions like
Na+, K
+,SO4
2-, Cl
- etc., On the other hand demineralised water does not contain
both anions and cations.
2 CO1
UNIT –II CORROSION AND PROTECTIVE COATING
1 State Pilling-Bedworth rule. CO2 (K1)
According to Pilling – Bedworth rule, if the volume of the oxide layer less than the volume of the metal, the oxide layer is porous and non-protective. 1. Example: Oxides of alkali and alkaline earth metals such as Na, Mg,
Ca, etc., 2. On the other hand, if the volume of the oxide layer is great volume of the metal, the oxide layer is non- porous and protective. 3.
Example: Oxides of heavy metals such as Pb, Sn, etc,
2 CO2 (K1)
2 Why does Mg corrode faster than iron?
CO2
(K2)
Galvanic corrosion occurs. Mg (more active or higher in emf series) dissolves in preference to iron(less active metal) i.e Mg acts anode and undergoes corrosion and Fe acts as cathode. It can be prevented by providing insulation between the two metals.
2 CO2
3 Bolt and nut of same metal is preferred in practice. Why? CO2 (K2)
It is preferred in practice, because galvanic corrosion is avoided due to homogeneous metals (no anodic and cathodic part)
2 CO2 (K2)
4 What is pitting corrosion? CO2 (K1)
Pitting is a localized attack, resulting in the formation of a hole around which the metal is relatively unattacked. Example: Ex: Metal area covered by a drop of water, sand, dust etc
2 CO2 (K1)
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5 List the differences between chemical corrosion and electrochemical
corrosion.
CO2 (K2)
Chemical corrosion Electrochemical corrosion
It occurs dry state
It occurs in the presence of moisture or
electrolyte
It follows adsorption
mechanism It follows electrochemical reaction
Corrosion product accumulate
on the same spot, where
corrosion occurs.
Corrosion occurs at anode while
products gather at cathode
2 CO2 (K2)
6 What are the advantages of electroless plating over electroplating.
CO2 (K1)
i)No electricity is required
ii) Electroless plating on insulators (like plastics,glass) and semiconductors
can be easily carried out.
iii)Complicated parts can also be plated uniformly.
iv) Electroless coating possesses good mechanical, chemical, and magnetic
properties.
2 CO2 (K1)
7 What are the requisites of a good paint? (K1) CO2 (K1)
It should spread easily on the metal surface
It should not crack on drying
The colour of the paint should be stable
It should be corrosion and water resistant
2 CO2 (K1)
8 What is differential aeration corrosion? CO2 (K1)
Differential aeration is nothing but two different concentration of air on a metal surface.
2 CO2 (K1)
9 What is galvanizing? CO2 (K1)
The process of coating molten zinc over the base metal is known as
galvanizing.
2 CO2 (K1)
10 What is hydrogen embrittlement? (K1)
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The process of formation of cracks and blisters on the metal
surface due to high pressure of hydrogen gas is called hydrogen embrittlement.
2 CO2 (K1)
11 Zinc is more readily corroded when coupled with copper than with lead why? CO2 (K2)
Zinc is anodic to Cu and Pb. When zinc is (E0= -0.76V) is coupled
with copper (E0= + 0.34V) zinc is more readily corroded, because the
difference in their position in emf series is more. Also Cu has (+)ve
reduction potential. But if Zn is coupled with lead (E0= -0.13V) rate
corrosion is less because the difference in their position in emf series is
less. Also Pb has (-) ve reduction potential.
2 CO2 (K2)
12 What is water line corrosion? CO2 (K1)
This type of corrosion occurs when a metal is exposed to carying concentration of oxygen or any electrolyte on the surface of the base metal. Here the metal above the water is more aerated and becomes cathodic, the part below the water is less aerated and becomes anodic. Example:
Metals partially immersed in a water (or) conducting solution
2 CO2 (K1)
13 What type of corrosion will occur to a Zn – Fe couple immersed in an
electrolyte? How can it be prevented?
CO2 (K2)
Galvanic corrosion occurs. Zinc (more active or higher in emf series) dissolves in preference to iron(less active metal) i.e Zn acts anode and undergoes corrosion and Fe acts as cathode. It can be prevented by providing insulation between the two metals.
2 CO2 (K2)
14 What is electroplating? CO2 (K1)
Electroplating is the process in which the coating metal is deposited on the base metal by passing a direct current through an electrolytic solution containing the soluble salt of the coating metal
2 CO2 (K1)
15 What is galvanic corrosion? CO2 (K1)
When two different metals are in contact with each other in presence of an aqueous solution or moisture, galvanic corrosion occurs.
2 CO2
UNIT III – POLYMER AND NANO TECHNOLOGY
1 Distinguish between thermoplastic and thermosetting plastics. CO3 (K2)
Thermo plastics: Thermosetting plastics
Formed by addition polymerization Formed by condensation polymerisation
Consists of long chain polymers consists of three dimensional network
Held together by weak vander waals forces held together by strong covalent bond
Weak,soft and less brittle Strong, hard and more brittle
2 CO3 (K2)
2 Define polymer & monomer?
CO3 (K1)
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Polymers are macro molecules formed by the repeated linking of large number of small
molecules. Monomer is a micro molecule which combines with each other to form a
polymer.
2 CO3 (K1)
3 Define functionality of a polymer CO3 (K1)
The number of bonding sites or reactive sites or functional groups present in a monomer. 2 CO3 (K1)
4 Define Polymerisation CO3 (K1)
Large number of small molecules combines to give a big molecule with or without
elimination of small molecules like water.
2 CO3 (K1)
5 Define Degree of polymerisation CO3 (K1)
The number of repeating units in a polymer chain. 2 CO3 (K1)
6 Classify the polymers on the basis of their tactility? CO3 (K1)
Foreign substance (sensitizer), absorbs light and gets excited. When the excited foreign
substance collides with another substance it gets converted in to some other product due
to the transfer of its energy
2 CO4 (K1)
7 What are chromophores? Give an example.
CO4 (K1)
One or more unsaturated linkage is responsible for the colour of the compound eg: C=C,
-NO , -N=N
2 CO4 (K1)
8 What if finger print region? CO4 (K1)
The vibration spectral region at 1400 – 700 cm -1 gives very rich and intense absorption
bands which is unique for each molecule. This region is termed as Finger Print Region.
2 K1 (K1)
9 Write the keto enal tautomerism of ethyl acetoacetate CO4 (K1)
keto form λ Max.275 nm, Enol form λ Max. 244 nm
2 CO4 (K1)
10 Calculate the number of modes of (IR) vibration for the following molecules.1. Non-linear (CH4)
2. Linear molecule(CO2)
CO4 (K2)
(a) CH4 (Non linear molecule) = 3N- 6 = (3 x 5) – 6 = 9
(b) CO2 (linear molecule) = 3N- 5 = (3 x 3) – 5 = 4
2 K1 (K2)
11 Mention three applications of UV-Visible Spectroscopy CO4 (K1)
concentration of unknown solution ,identification of aromatic compounds ,detecting
impurities
2 CO4 (K1)
12 Define the term – Bathochromic shift, Hypsochromic shift CO4 (K1)
Bathochromic shift: shifting of absorption band towards a longer wavelength.
Hypsochromic shift: shifting of absorption band towards a shorter wavelength.
2 CO4 (K1)
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13 Write any two limitations of Beer-Lamberts law? CO4 (K1)
1. Radiation used is monochromatic.
2. Applicable only for dilute solutions.
3. Temperature of the system should not be allowed to vary to a larger extent.
2 CO4 (K1)
14 What is the relation between wavelength, frequency and wave number? CO4 (K1)
1/λ = υ = υ/c
2 CO4 (K1)
15 What are the factors which affect the absorbance of the photons by a molecule?
CO4 (K1)
1.The nature of the absorbing molecules
2. The concentration of the molecules
3. Path length of radiation
2 CO4 (K1)
PART – B (12 Mark Questions with Key)
S.
N
o
Questions Mark COs BTL
UNIT I –WATER TECHNOLOGY
1 How will you protect boiler from corrosion. 12 CO1 (K2)
4
a)Chemical method:
Sodium sulphite, hydrazine are some of the chemicals used for
removing oxygen.
(b)Mechanical de-aeration:
4
4
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Dissolved oxygen can also be removed from water by mechanical
deaeration.
In this process, water is allowed to fall slowly on the perforated
plates fitted inside the tower.
The sides of the tower are heated, and a vacuum pump is also
attached to it.
The high temperature and low pressure produced inside the tower
reduce the dissolved oxygen content of the water.
Mechanical de-aeration of water
(c)Removal of dissolved Carbon dioxide:
Carbon dioxide can be removed from water by adding a calculated
amount of NH4OH into water.
Carbon dioxide along with oxygen can also be removed mechanically by
de-aeration method.
(d) Removal of acids:
Corrosion by acids can be avoided by the addition of alkali to the boiler
water.
2 How can the effect of caustic embrittlement in boiler be resolved? 12
CO1 (K2)
Caustic embrittlement means intercrystalline cracking of boiler
metal.
Boiler water usually contains a small proportion of Na2CO3. In
high pressure boilers this Na2CO3 undergoes decomposition to
give NaOH.
3
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This NaOH flows into the minute hair cracks and crevices, usually
present on the boiler material, by capillary action and dissolves
the surrounding area of iron as sodium ferroate.
This causes embrittlement of boiler parts, particularly stressed
parts like bends, joints, rivets, etc., causing even failure of the
boiler.
Prevention:
Caustic embrittlement can be prevented by
(i) Using sodium phosphate as softening agent instead of sodium
carbonate.
(ii) By adding tannin, lignin to the boiler water, this blocks the
cracks.
4
3 Identify the problems created in boilers if priming and foaming takes
place 12
CO1 (K2)
(a)Priming:
Priming is the process of production of wet steam.
3
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Priming is caused by
(i) High steam velocity.
(ii) Very high water level in the boiler.
(iii) Sudden boiling of water.
(iv) Very poor boiler design.
Priming can be controlled by
(i) Good boiler design.
(ii) Using treated water.
(b)Foaming:
The formation of stable bubbles above the surface of water is
called foaming.
Foaming is caused by the
(i) Presence of oil, and grease,
(ii) Presence of finely divided particles.
Foaming can be prevented by
(i) Adding coagulants like sodium aluminate, aluminium
hydroxide,
(ii) Adding anti-foaming agents like synthetic polyamides.
3
3
3
4 Describe the Reverse Osmosis method for desalination of water. 12
CO1 (K2)
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4
Desalination
The process of removing common salt (sodium chloride)
from the water is known as desalination.
Desalination is carried out either by reverse osmosis or
electro dialysis.
Reverse osmosis
When two solutions of different concentrations are separated by a
semi-permeable membrane, solvent (water) flows from a region of
lower concentration to higher concentration. This process is called
osmosis.
The driving force in this phenomenon is called osmotic pressure.
When the solvent flows from higher concentration to lower
concentration through a semi-permeable membrane is called
reverse osmosis.
Thus, in the process of reverse osmosis pure water is separated
from salt water. This process is also known as super-filtration.
The membranes used are cellulose acetate, cellulose butyrate, etc.
Advantages:
(i) The life time of the membrane is high, and it can be replaced
within few minutes.
(ii) It removes ionic as well as non-ionic, colloidal impurities.
(ii) Due to low capital cost, simplicity, low operating, this process is
3
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used for converting sea water into drinking water.
5 What are zeolites? How do they function in removing the hardness of
water? 12
CO1 (K2)
4
Zeolites is porous and possess gel like structure, hence it is generally used
for water softening. It 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
When hard water is passed through a bed of sodium zeolite (Na2Ze),
kept in a cylinder, it exchanges its sodium ions with Ca2+
and Mg2+
ions
present in the hard water to form calcium and magnesium zeolites. The
various reactions taking place during softening process are
CaSO4+ Na2Ze→CaZe+Na2SO4
The softened water is enriched with large amount of sodium salts,
which do not cause any hardness, but cannot be used in boilers.
Regeneration
3
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After some time zeolite gets exhausted. The exhausted zeolite is again
regenerated by treating with 10% solution of NaCl.
CaZe+2NaCl→Na2Ze+CaCl2
Advantages of Zeolite process
Water will have only hardness of 1-2 ppm.
No sludge is formed during this process.
Its operation is easy.
Disadvantages of Zeolite process
Turbid water cannot be treated.
Acidic water cannot be treated.
Water containing Fe, Mn cannot be treated
2
6 Explain the following boiler troubles suggesting the remedial methods: (i)
Scale and sludge formation (ii) Priming and foaming. 12
CO1 (K2)
(a)Sludge (b)Scale
2
Sludge (Loose deposit)
If the precipitate is loose and slimy it is called sludge.
Sludges are formed by substances like MgCl2, MgCO3, MgSO4
and CaCl2.
2
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They have greater solubilities in hot water than cold water.
Scale (Hard deposit)
On the other hand, if the precipitate forms hard and adherent
coating on the inner walls of the boiler, it is called scale.
Scales are formed by substances like Ca(HCO3)2,CaSO4 and
Mg(OH)2.
Prevention of scale formation:
They can be removed by using scraper, wire brush etc.
They can be removed by thermal shocks.
By using suitable chemicals like dil.acids.
Priming:
Priming is the process of production of wet steam.
Priming is caused by
(i) High steam velocity.
(ii) Very high water level in the boiler.
(iii) Sudden boiling of water.
(iv) Very poor boiler design.
Priming can be controlled by
(i) Good boiler design.
(ii) Using treated water.
Foaming:
The formation of stable bubbles above the surface of water is
called foaming.
Foaming is caused by the
(i) Presence of oil, and grease,
2
3
3
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(ii) Presence of finely divided particles.
Foaming can be prevented by
(i) Adding coagulants like sodium aluminate, aluminium
hydroxide,
(ii) Adding anti-foaming agents like synthetic polyamides.
UNIT II - CORROSION AND ITS CONTROL
1 Illustrate the mechanism involved in electrochemical corrosion. 12
CO2 (K2)
Wet (or) Electro -Chemical Corrosion
(i) When two dissimilar metals or alloys are in contact with each other in
the presence of an aqueous solution or moisture.
(ii) When a metal is exposed to varying concentration of oxygen or any
electrolyte.
Mechanism of wet corrosion
At anode
In anodic part, oxidation (or) dissolution of metal occurs
At cathode
(a) Acidic environment
If the corrosive environment is acidic, hydrogen evolution occurs at
cathodic part.
(b) Neutral environment
If the corrosive environment is slightly alkaline (or) neutral, hydroxide
ions are formed at cathodic part.
(a) Hydrogen evolution type corrosion
“All metals above hydrogen in the electrochemical series have a tendency
to get dissolved in acidic solution with simultaneous evolution of hydrogen
gas”
Example
3
3
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At anode
At cathode
(b) Absorption of oxygen (or) Formation of hydroxide ion type corrosion
The surface of iron is usually, coated with a thin film of iron oxide.
However, if the oxide film grows, some crack will form and anodic areas are
created on the surface while the remaining part acts as cathode
Example
At anode
At cathode
3
2 Describe the factors influencing chemical & electrochemical corrosion.
12 CO2 (K2)
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The rate of corrosion is mainly depends on
1.Nature of the metal
2.Nature of the environment
Nature of the metal:
(i)Position in emf series
Metals above the hydrogen in emf series get corroded vigorously. Lower
the reduction potential, greater is the rate of corrosion.
When two metals are in electrical contact, the more active metal (or the
metal having high negative reduction potential) undergoes corrosion.
(ii)Relative areas of the anode and cathode
The rate of corrosion will be more, when the cathodic area is larger
(iii)Purity of the metal
The 100% pure metal will not undergo any type of corrosion. Higher the
percentage of impurity, faster is the rate of corrosion of the anodic metal.
(iv)Over voltage or over potential
(v)Nature of the surface film
(vi)Nature of the corrosion product
If the corrosion product is soluble in the corroding medium, the corrosion
rate will be faster.
Nature of the environment
i) Temperature
The rate of corrosion increase with temperature
ii) Humidity
Rate of corrosion will be more, when the humidity in the
environment is high.
iii) Presence of corrosive gases
The acidic gases like CO2,SO2,H2S increases the
electrochemical corrosion.
iv) Presence of suspended particles
It accelerate the electrochemical corrosion
v) Effect of pH The rate of corrosion will be maximum when the corrosive environment is
acidic
6
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(ie) pH is less than 7.
3 Explain the Electroless Nickel plating 12
CO2 (K2)
Principle Electroless plating is a technique of depositing a noble metal (from its salt solution) on a catalytically active surface of the metal, to be protected, by using suitable reducing agent without using electrical energy.
Step I
Pretreatment and activation of the surface
Step II
Preparation of Plating bath
The plating bath consists of the following ingredients
Step III
Procedure for plating
Nature of the
compound
Name of the
compound
Quantity
(g/l)
Function
Coating solution NiCl2 20 Coating metal
Reducing agent Sodium
hypophosphite
20 Metal ions
reduced
Complexing
agent cum exhaltant
Sodium succinate 15 Improves the
quality
Buffer Sodium Acetate 10 Control of pH
Optimum pH 4.5 - -
Optimum
Temperature
930C - -
3
3
3
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Various reactions
At Cathode
At Anode
Net reaction
Applications
4 Explain differential aeration corrosion and galvanic corrosion with
suitable illustrations. 12
CO2 (K2)
This type of corrosion occurs when a metal is exposed to varying
concentration of oxygen or any electrolyte on the surface of the base metal.
Example
Metals partially immersed in water (or) conducting solution (called
water line corrosion).
If a metal is partially immersed in a conducting solution (Fig. 3.6) the metal
part above the solution is more aerated and hence become cathodic.
On the other hand, the metal part inside the solution is less aerated and
thus, become anodic and suffers corrosion.
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At anode (less aerated part)
At cathode (more aerated part)
Examples for Differential aeration corrosion (a) Pitting or localised corrosion.
(b) Crevice corrosion.
(c) Pipeline corrosion.
(d) Corrosion on wire fence.
(a) Pitting corrosion Pitting is a localised attack, resulting in the formation of a
hole around which the metal is relatively unattacked.
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(b) Crevice corrosion If a crevice between different metallic objects or between metal and non-
metallic material is in contact with liquids, the crevice becomes the anodic
region and suffers corrosion.
This is due to less oxygen in crevice area. The exposed areas act as
cathode
c) Pipeline corrosion Differential aeration corrosion may also occur in different parts of
pipeline.
Buried pipelines or cables passing from one type of soil to another say,
from clay (less aerated) to sand (more aerated) may get corroded due to
differential aeration.
(d) Corrosion on wire-fence Fig. 3.10 shows a wire fence in which the areas where the wires cross
are less aerated than the rest of the fence and hence corrosion occurs at the wire
crossings, which are anodic.
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5 Explain the process of electro deposition taking a suitable example.
12 CO2 (K2)
Process
Various chemical reactions
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4
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At Cathode
At Anode
Characteristics of Copper Plating
6 Explain Dry (or) Chemical corrosion
12 CO2 (K2)
Dry corrosion is due to the attack of metal surfaces by the atmospheric
gases such as oxygen, hydrogen sulphide, sulphur dioxide, nitrogen, etc.
There are 3 main types of dry corrosion.
1. Oxidation corrosion (or) corrosion by oxygen.
2. Corrosion by hydrogen.
3. Liquid-metal corrosion.
1. Oxidation corrosion (or) corrosion by oxygen Oxidation corrosion is brought about by the direct attack of oxygen at low or
high temperatures on metal surface in the absence of moisture.
Mechanism of dry Corrosion
3
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Nature of oxide film
1. Stable oxide layer Such a film behaves as a protective coating and no further
corrosion can develop.
Example
2. Unstable oxide layer Unstable oxide layer is mainly produced on the surface of noble metals,
which decomposes back into the metal and oxygen.
Example
3. Volatile oxide layer
The oxide layer volatilizes as soon as it is formed, leaving the metal
surface for further corrosion.
Example
4. Protective (or) Non-Protective oxide film (Pilling- Bedworth rule)
According to Pilling – Bedworth rule, if the volume of the
oxide layer formed is less than the volume of the metal, the oxide layer is porous and non-protective.
On the other hand, if the volume of the oxide layer formed is greater than the volume of the metal, the oxide layer is non- porous and protective.
2. Corrosion by hydrogen
3
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Components:Radiation source: The main source of radiation is Nichrome wire or Nernst
glower which is a filament containing oxides of Zr, Th, Ce held together with a binder.
2
Monochromators: It allows the light of the required wavelength to pass through light of other
Sample cell: The cells must be transparent to IR radiation are used to hold the sample.
2
Detector: Detectors are used to convert thermal radiant energy into electrical energy. 1
Recorder: The recorder record the signal coming out from the detector 1
Working:The radiation emitted by the source is split into two parallel beams. One of the
beams passes through the sample and the other passes through the reference sample. When the
two beams of light recombine they produce a signal which is measured by detector. The signal
from the detector is recorded by the recorder
2
5 Identify any one analytical method to estimate sodium present in aqueous media. 12 CO4 (K2)
Principle: Flame photometry is based on the measurement of intensity of the light emitted
when a metal is introduced into a flame.
Principle:
Evoporation Vapourisation Dissociation
M+X- MX MX
Thermal Excitation h Emission
X+ M M* M (ground state)
(excited state)
2
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Instrumentation
Burner - flame excitation unit Mirror -radiation is emitted: to increase amount of radiation concave mirror used Slits - entrance slits: permit radiation
- allows the light of required wavelength Detector – measures the intensity of radiation -
converts radiation in to electric current.
Amplifier - record the current.
2
Working
Air + Sample solution + Fuel gas mixture
Burnt in burner
Radiation emmited and passed
Lens,Filter, Detector, Amplifier,Recorder.
Expt carried out for series of std.solutions
Graph plotted between concentration and intensity of emitted light.
2
ESTMATION OF SODIUM BY FLAME PHOTOMETRY
Instrument is switched on
Air & gas supply regulated
Distilled water is sent.
Warmed for 10 mins
Instrument adjusted for zero degree
Sodium produced yello emission at 589 nm , the instruments is set
Readings are noted for series of NaCl
5
Graph plotted between concentration and intensity of emitted light.
1
6 Discuss the applications of UV-Spectroscopy. 12 CO4 (K2)
Predicting relationship between different group 2
Detection of impurities: UV Visible spectroscopy is the best method for detecting impurities
in organic compounds because
The bands due to impurities are very intense.
Saturated compounds have weak absorption band and unsaturated compounds have
strong absorption band.
2
The kinetics of chemical reaction: The progress of a chemical reaction can be easily followed
by examining the UV-spectra of test solution at different time intervals. The concentration of
either the reactant or product can be followed
2
Determination of calcium in blood serum. Calcium in blood serum in indirectly determined
by converting the Ca present in 1 ml of serum as calcium oxalate, and dissolving the calcium
oxalate in dilute sulphuric acid and treated with ceric sulphate solution.
2
Quantitative analysis: UV absorption spectroscopy is used for the quantitative determination 2
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of compounds based on Beer-Lambert‟s law.
Dissociation constant of acid and bases pKa=pH+log(HA)/(A-)
Study of tautomeric equilibrium, Determination of molecular weight 2
Note : 6 Questions with answer key must be prepared in each unit and maximum two sub divisions are allowed.
PART – C (20 Mark Questions with Key)
S.No Questions Ma
rk
C
Os
BTL
UNIT I – WATER TECHNOLOGY
1 Explain the demineralization of water by ion exchange process. How are exhausted
cation and anion exchange resins regenerated?
20 C
O
1
(K2)
6
This process removes almost all the ions (both anions and cations) present in hard water.
Demineralization process is carried out by using ion exchange resins.
1. Cation exchanger
Resins containing acidic functional groups (-COOH,-SO3H) are capable of exchanging their
H+ ions with other cations of hard water. It is represented as RH2.
2. Anion exchanger
Resins containing basic functional groups (-NH2,-OH) are capable of exchanging their anions
with other anions of hard water. It is represented as R (OH) 2.
Process
The hard water first passed through a cation exchange column, which absorbs all the cations
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like Ca
2+, Mg
2+, Na
+, K
+, etc., present in the hard water.
RH2+CaCl2 → RCa+2HCl
RH+NaCl → RNa+HCl
The cation free water is then passed through a anion exchange column, which absorbs
all the anions like Cl-, SO4
2-,HCO3
-,etc., present in the water.
R’ (OH)2+2HCl →R’Cl2+2H2O
The water coming out of the anion exchanger is completely free from cations and
anions. This water is known as demineralised water or deionised water.
Regeneration
When the cation exchange resin is exhausted, it can be regenerated by passing a solution of dil
HCl or dil H2SO4.
Similarly, when the anion exchange resin is exhausted, it can be regenerated by passing a
solution of dil NaOH.
3
2 Explain internal treatment of boiler feed water 20 C
O
1
(K2)
Carbonate conditioning
Scale formation can be avoided by adding Na2CO3 to the boiler water. It is
used only in low pressure boilers. The scale forming salt like CaSO4 is converted into
CaCO3, which can be removed easily.
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Phosphate conditioning
Scale formation can be avoided by adding sodium phosphate. It is used in high pressure boilers.
The phosphate reacts with Ca2+
and Mg2+
salts to give soft sludges of calcium and magnesium
phosphates.
Generally 3 types of phosphates are employed
Colloidal conditioning
Scale formation can be avoided by adding colloidal conditioning agents
like kerosene, agar-agar, gelatin, etc., It is used in low pressure boilers.
These colloidal substances get coated over the scale forming particles
and convert them into non-adherent, loose precipitate called sludge,
which can be removed by blow down operation.
Calgon conditioning
Calgon is sodium hexa meta phosphate Na2 [Na4(PO3)6]. This substance
interacts with calcium ions forming a highly soluble complex and thus
prevents the precipitation of scale forming salt.
The complex Na2 [Ca2 (PO3)6] is soluble in water and there is no problem
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of sludge disposal. So calgon conditioning is better than phosphate conditioning.
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UNIT II - CORROSION AND PROTECTIVE COATING
1 Name the chief constituents of paints and explain their functions. 20 C
O
2
(K2)
Paint is a mechanical dispersion of one or more finely divided pigments in a
medium (thinner vehicle). When a paint is applied to a metal surface, the thinner
evaporates, while the vehicle undergoes slow oxidation forming a pigmented film.
Constituents and their functions of a paint
1. Pigments :
Pigments are colour producing substances in the paint
Functions
(i)It gives colour and opacity to the film.
(ii) It also provides strength to the film.
(iii) It protects the film by reflecting the destructive uv rays.
(iv) It increases weather resistance of the film.
2. Vehicle (or) drying oil:
This is non volatile portion of a medium and film forming constituents of
paint.These are high molecular weight fatty acids present in vegitable and animal oils.
Functions
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3
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Thinners (or) solvents
Functions
4. Extenders (or) fillers
Functions
Driers
Functions
Plasticisers
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2
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Anti-skinning agents
2
2
2 Explain sacrificial anode and impressed current cathodic techniques for the
prevention of corrosion.
20 C
O
2
(K2)
The principle involved in the electrochemical protection (or) cathodic protection is
to force the metal to behave like a cathode. The important cathodic protections are
(i) Sacrificial anodic protection
(ii) Impressed current cathodic protection
1. Sacrificial anodic protection method
In this method, the metallic structure to be protected is made cathode by
connecting it with more active metal .
So that all the corrosion will concentrate only on the active metal. The
artificially made anode thus gradually gets corroded protecting the original metallic
structure. Hence this process is otherwise known as sacrificial anodic protection.
Aluminium, Zinc, Magnesium are used as sacrificial anodes.
Applications of sacrificial anodic protection
(a) This method is used for the protection of ships and boats. Sheets of Mg or Zn
are hung around the hull of the ship (Fig. 3.17). Zn or Mg will act as anode compared to
iron (ship or boat is made of iron), so corrosion concentrates on Zn or Mg. Since they
are sacrificed in the process of saving iron, they are called sacrificial anodes.
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(b) Protection of underground pipelines, cables from soil corrosion
(c) Insertion of Mg sheets into the domestic water boilers to prevent the formation
of rust
(d) Calcium metal is employed to minimize engine corrosion.
2. Impressed current cathodic protection method
In this method, an impressed current is applied in the opposite direction of
the corrosion current to nullify it, and the corroding metal is converted from anode to
catho This can be done by connecting negative terminal of the battery to the metallic
structure, to be protected, and positive terminal of the battery is connected to an inert
anode. Inert anodes used for this purpose are graphite, platinised titanium. The
anode is buried in a “back fill” (containing mixture of gypsum, coke, breeze,
sodium sulphate). The “back fill” provides good electrical contact to anode
Applications of impressed current protection Structures like tanks, pipelines, transmission line towers, underground water
pipe lines, oil pipe lines, ships, etc., can be protected by this method.
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4
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UNIT III – POLYMER AND NANO TECHNOLOGY
1 Explain the mechanism of free radical polymerization 20 C
O
3
(K2)
i) Initiation
Initiation involves two reactions.
a) First Reaction
First Reaction involves production of free radicals by homolytic dissociation of an initiator (or
catalyst) to yield a pair of free radicals (R
.)
b) Second Reaction
Second Reaction involves addition of this free radical to the first monomer to produce chain
initiating species.
ii) Propagation
It involves the growth of chain initiating species by the successive addition of large number of
monomers.
iii) Termination
Termination of the growing chain of the polymer occurs either by coupling reaction or
disproportionation.
a) Coupling (or) Combination
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It involves coupling of free radical of one chain end to another free radical to form
macromolecule (dead polymer).
b) Disproportionation
It involves transfer of a hydrogen atom of one radical centre to another radical centre forming two
macromolecules, one saturated and another unsaturated.
The products of addition polymerisation is known as dead polymers. 2 Explain in Detail the fabrication process of plastics through compression moulding
20 C
O
3
(K2)
Compression Moulding is a method of moulding in which the moulding material, generally preheated, is
first placed in an open, heated mould cavity. The mold is closed with a top force or plug member,
pressure is applied to force the material into contact with all mold areas, while heat and pressure are
maintained until the molding material has cured. The process employs thermosetting resins in a partially
cured stage, either in the form of granules, putty-like masses, or preforms.