DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI

DEPARTMENT OF MECHANICAL ENGINEERING

CY6251 ENGINEERING CHEMISTRY – II

UNIT – I : WATER TECHNOLOGY

PART – A (2 MARKS)

1. What are ion-exchange resins? (M - 11)

Ion-Exchange Resins are long chain, insoluble, cross linked, organic polymers which are capable of exchanging its ions with water. They are of 2 types. a) Cation exchange resins – RH+ (e.g) Sulphonated coals ,RSO3H

b) Anion exchange resins – R‟OH- (e.g) Urea formaldehyde, Amines R-NH2.

2. Distinguish between soft water and demineralized water. (M - 11)

Soft water Demineralized water It does not contain hardness producing calcium and magnesium ions, but it may

contain other ions like K+, Na+, Cl- etc.

Demineralized water does not contain any ions including hardness producing ions.

Softening involves removal of only hardness causing ions.

Demineralization involves removal of all the ions present in water.

3. What are Boiler troubles? How are they caused? (M- 07)

Sludge and Scale formation , Caustic embrittlement , Boiler corrosion, Priming and foaming are collectively

known as boiler troubles. They are caused by the hardness causing salts present in boiler feed water.

4. What is caustic embrittlement? How can it be prevented? (M - 12, M - 14)

It is the inter-crystalline cracking of boiler due to NaOH. NaOH content is increased due to the dissolved salts like

Na2CO3 which is added during internal treatment. To prevent caustic embrittlement: i.)Sodium phosphate can be

used as softening agent instead of Na2CO3 ii) The hair line cracks can be sealed by waxy materials like tannin and lignin.

5. What are scales? How can their formation be prevented? Mention the

disadvantages of scales. (M - 09)

Scales are hard, thick and adherent precipitate deposited on boilers due to salts like CaSO4 , Ca(HCO3)2

present in water. Disadvantages: Wastage of fuel - Lowering of boiler safety - Decrease in efficiency of boilers - Danger of explosion Prevention methods:

1. Internal treatment methods (eg) Calgon conditioning 2. External treatment methods (eg) Ion-exchage method.

3. By using mechanical scrubber.

6. What is priming and foaming?

Priming: When boiler is producing steam rapidly, some particles of the liquid water are carried along-with steam. This process of wet steam formation is called priming. Foaming: It is the production of persistent foam or stable bubbles in boilers, which do not break easily.

7. What is meant by „internal conditioning of water‟? Name any two boiler

compounds used in internal conditioning of boiler feed water. The residual salts which are not removed by external methods can be removed by adding some chemicals directly into the boiler water. These chemicals are known as „Boiler compounds’. This method is known as internal conditioning of water‟ Eg : Carbonate conditioning – Sodium carbonate, Phosphate conditioning – Sodium phosphate.

8. What is the role of phosphates in the internal treatment of water? (or) Name an

internal method used for high pressure boiler and explain. (N - 11)

Phosphate salts are used as internal boiler compounds for high pressure boilers. Phosphates precipitate the soluble Ca and Mg salts as their insoluble phosphates. They are also helpful in maintaining the pH of the boiler water.

3CaSO4 + 2 Na3PO4 → Ca3(PO4)2 + 3 Na2SO4

Three types of Phosphate salts are used:

S.N o

Salt Name of the salt Used for treating

1 Na3PO4 Tri sodium Phosphate highly acidic water 2 Na2HPO4 Di sodium hydrogen Phosphate slightly acidic water 3 NaH2PO4 Sodium di hydrogen phosphate highly alkaline water

9. Calgon treatment prevents scale formation in boilers. Give reason. (M – 10 , M – 11& M - 14)

Addition of calgon (sodium hexa meta phosphate) to boiler feed water interacts with calcium ions in the CaSO4

forming a soluble complex, thus preventing the precipitation of scale and sludge forming salt.

2CaSO4+ Na2[Na4(PO3)6] Na2[Ca2(PO3)6] + 2Na2SO4.

Soluble complex.

10. What do you understand by demineralization of water ? What are the

advantages and disadvantages of demineralization process?

During this process cations and anions of water are completely removed. It uses two columns of cation - exchange column and anion- exchange column filled with resins Advantages: The process can be used to soften highly acidic or alkaline waters. It produces water of very low hardness (2 ppm). It is very good for treating water for use in high-pressure boilers.

Disadvantages: The equipment is costly and more expensive. The turbidity must be below 10ppm.

11. How is the exhausted zeolite softener bed regenerated?

Exhausted zeolite can be regenerated by using 10% brine (NaCl) solution.

CaZe + 2NaCl → Na2Ze +CaCl2

12. What is coagulation?

Coagulation is the process of removing fine suspended and colloidal impurities by the addition of requisite amount of chemicals (called coagulants) to water before sedimentation.

Ex: Al2(SO4)3 +3Ca(HCO3)2 2 Al(OH)3 + 3 CaSO4 + 6CO2

13. What is reverse osmosis? Mention some of its advantages. (N - 11)

When we apply an excess and opposite Hydrostatic pressure to overcome the osmotic pressure, then higher

concentrated solvent will flow to the lower one. This is known as reverse osmosis. Advantages: i) It removes ionic and non-ionic, colloidal and high molecular weight organic matter. ii) It removes colloidal silica, which is not removed by demineralization iii) The life time of membrane is quite high, about 2 years. The membrane can be replaced within a few minutes, thereby providing uninterrupted water supply.

14. What is Desalination? Name the different methods of desalination. (M - 11)

Removal of common salt (NaCl) from water is called „Desalination‟. Various methods of desalination: Reverse Osmosis, Distillation, Electro- dialysis, Freezing, Solar distillation, etc.

15. What are the requirements (or) requisites of boiler feed water?

Water used in boilers known as boiler feed water must be free from a.Hardness producing salts (Ca2+, Mg2+ions)

b.Suspended impurities like silica, oil,etc. (iii)Dissolved gases like O2, CO2,etc. 16. What are boiler compounds? Give examples.

Boiler compounds are chemicals added inside the boilers to remove scale forming substances. Eg: Sodium carbonate, Calgon, Sodium phosphate.

17. Zeolite softener cannot be used for softening turbid water. Why?

The suspended matters in turbid water clogs the pores of the zeolite bed and restrict the water flow.

18. Zeolite softeners cannot be used for softening brackish water. Why?

The softening of brackish water involves the removal of sodium ions. Since sodium zeolite is a cation exchanger, the exchange of same cation does not produce any softening.

19. What are the merits of ion – exchange process?

Highly acidic and alkaline water can be treated.

Residual hardnesss of the water is 0-2 ppm. So it is very good for use in high pressure boilers.

Resins can be regenerated.

20. How will you regenerate the column in demineralization process?

The exhausted cation exchange resin is regenerated by passing dil.HCl or dil.H2SO4. The exhausted anion exchange resin is regenerated by passing dil. NaOH.

21. What are the merits and demerits of zeolite process?

Merits: (i) The softened water has hardness between15-50ppm. (ii) Requires less time for softening

(iii) No sludge is formed during this process. Demerits:

(i) The treated water contains more sodium salts which cannot be used as boiler feed water. (ii) Highly turbid water cannot be treated by this method. (iii) Zeolite plant occupies more space.

22. What is meant by colloidal conditioning?

Formation of scale in boilers can be avoided by adding organic substances like kerosene, tannin, agar- agar, etc. these substances get coated over the scale forming precipitates thereby yielding non-sticky deposits which can be removed.

23. What is boiler corrosion?

Boiler corrosion is the decay of boiler material by a chemical or electrochemical attack. It is due to the

presence of dissolved gases such as CO2, O2 and the salt like MgCl2. Mechanical deaeration is used to

remove dissolved gases such as CO2 and O2.

24. Distinguish between Zeolite process and demineralization process.

S.N o.

Zeolite process Demineralization process

1. Exchange only cations Exchange cations as well as anions. 2. Acidic water cannot be treated since acid

decomposes the zeolite Acidic water can be treated.

3. Zero hardness cannot be achieved Zero hardness can be achieved 4. The treated water contains large amount of

dissolved salts which leads to caustic embritttlement in boilers.

The treated water does not contain any ions and therefore it can be safely used in boilers.

25. What is blow - down operation?

It is a process in which a portion of concentrated water containing large amount of dissolved salts are replaced by fresh water frequently during steam production.

26. What are the differences between sludges and scales.

S.N o.

Sludges Scales

1. It is a soft, loose precipitate formed inside the boiler walls during steam production

It is hard, adherent coating formed on the inner walls of the boiler during steam production

2. Sludges are produced due to the presence of Scales are produced due to the presence temporary hardness causing compounds like of permanent hardness causing Ca(HCO3)2, Mg(HCO3)2 substances like

CaCl2,CaSO4,MgCl2,MgSO4

3. It is also produced due to the presence of suspended and colloidal impurities.

It is produced due dissolved salts.

to the presence of

PART – B (16 MARKS)

1. Describe the de-mineralisation of process of water softening. ( N-02, M-07, M-08)

2. How is exhausted resin regenerated in an ion-exchanger? What are the merits and the demerits of ion-exchange

method?

3. What are boiler troubles? How are they caused? How they are minimized by colloidal conditioning, phosphate &

calgon conditioning (M-14)

4. Discuss the causes and prevention of priming and foaming (M-06)

5. What is caustic embrittlement. How can it be prevented? (M-14)

6. What are scale and sludge. Describe the disadvantages of scale and sludge formation. (M-10)

7. Describe the Reverse osmosis method of desalination of water. (M-10, N-14)

8. With a neat diagram describe the ion exchange process of water softening. (M-14)

9. Discuss the disadvantages of using hard water in boiler.

10. How is the softening of water carried out using the Zeolite process? (M-14)

11. Describe briefly the various methods of internal conditioning of boiler feed water.

12. What are the boiler troubles? How are they caused?

Suggest steps to minimize the boiler troubles.

13. Discuss in detail the problems caused due to the usage of hard water in boilers. (M-06)

14. Explain the following boilers troubles suggesting the remedial methods:

i) Sludge and Scale formation ii) Caustic embrittlement. (M-14)

15. i) With a neat diagram describe the ionization process of water softening or what are ion exchange resins? How

are they useful in removing hardness of water. (M-14)

ii) How is internal treatment of boiler water carried out using phosphate, carbonate and calgon?

16. How will you protect boiler from corrosion of water or discuss the troubles in boiler feed water or discuss the

disadvantages of using hard water in boilers. (M-13)

17. What is desalination? With a neat diagram. Describe the reverse osmosis method for the desalination of

brackish water. Write its disadvantages? (N-14)

18. Explain zeolite or permutit prcess of purification of hard water. (M-13)

UNIT – II : ELECTROCHEMISTRY AND CORROSION

PART - A (2 MARKS)

1. What are the conditions for a cell to be reversible?

A cell will be reversible if it satisfies the following conditions, i) If Eappl =Ecell , no chemical reaction takes place ii) If Eappl > Ecell , chemical reaction will take place in reverse direction.

2. Define standard electrode potential. (M - 14)

The measure of tendency of a metallic electrode to lose or gain electrons when in contact with a solution of its own salt of 1M concentration at 25 0 C . Give the Nernst equation. For an electrode reaction, Mn+ (aq) + n e- → M (s) The Nernst‟s equation is, E Mn+/ M = E0 Mn+/ M +2.303RT/nF log [ Mn+ ]

3. What is the Significance of Nernst equation?

i. Used to calculate the single electrode potential. ii. Polarity of the electrode in an electrochemical cell can be determined.

4. What is single electrode potential? (N - 10) & (M - 11)

It is the tendency of a metallic electrode to lose or gain electrons when it is in contact with its own ions in solution. 5. Define EMF of a cell.

Electromotiveforce is defined as,"the difference of potential which causes flow of current from one electrode of higher potential to the other electrode of lower potential. Thus, the emf of a galvanic cell can be calculated using the followingrelationship.

E°cell = E°right − E°left 6. Distinguish between reversible and irreversible cells giving one example for

each.

S.No Reversible Cells Irreversible Cells

1. A cell which obeys the three conditions of thermodynamic reversibility are called reversible cell.

Cells which do not obey the conditions of thermodynamic reversibility are called irreversible cells.

2. Cell reaction is reversed when external potential greater than cell potential is applied.

The cell reaction is not completely reversed.

3. Daniel cell, secondary batteries (rechargeable batteries).

Zinc – silver cell, Dry cell (Primary Cells)

7. Suggest a method to determine the electrode potential of zinc.

The saturated calomel electrode is coupled with another Zn electrode, the potential of which is to be determined. Since the reduction potential of the coupled Zn electrode is less than E° of calomel electrode (+ 0.2422 V), the calomel electrode will act as cathode and the reaction is

E°Zn = + 0.2422 − 1.0025

E°Zn = − 0.7603 volt

8. What are reference electrodes? Give two examples. (N - 10)

The electrode potential is found out by coupling the electrode with another reference electrode, the potential of which is known or arbitrarily fixed as zero. Primary reference electrode: standard hydrogen electrode & Secondary reference electrode: calomel electrode.

9. Mention any two application of EMF measurement.

1. Determination of standard free energy change and equilibrium constant. 2. The standard free energy change of a reaction can be calculated as follows− ΔG° =nFE° 3. The equilibrium constant of a reaction can be calculated as follows.

E° = Standard emf of the cell; K = Equilibrium constant

10. Write down the formulation of the standard hydrogen electrode.

Hydrogen electrode consists of platinum foil, that is connected to a platinum wire and sealed in a glass tube. Hydrogen gas is passed through the side arm of the glass tube. This electrode, when dipped in a 1N HCl and hydrogen gas at 1 atmospheric pressure is passed, forms standard hydrogen electrode. The electrode potential of SHE is zero at all temperatures.

It is represented as,Pt, H2 (1 atm)/H+ (1 M); E° = 0.

11. Distinguish between electrochemical series and galvanic series.

Sl.No. Electrochemical series Galvanic series 1 When the various electrodes (metals)

are arranged in the order of their increasing values of standard reduction potential on the hydrogen scale, then the arrangement is called electrochemical series.

The metal electrodes are placed in sea water under std. conditions and the electrode potentials are measured. When these electrode potentials are arranged in the decreasing order, a series produced known as galvanic series.

2 This series comprises of metals and non-metals.

This series comprises metals and alloys

12. What is a secondary reference electrode? Give one example with its electrode potential value. (M - 06)

Calomel electrode consists of a glass tube containing mercury at the bottom over which mercurous chloride is

placed. The remaining portion of the tube is filled with a saturated solution of KCl. The bottom of the tube is sealed

with a platinum wire. The side tube is used for making electrical contact with a salt bridge. The electrode potential

of the calomel electrode is + 0.2422 V. It is represented as, Hg, Hg2Cl2(s), KCl (sat.solution);E° = 0.2422V

Ni2+/Ni Cu2+/Cu 13. Can we use a nickel spatula to stir a solution of copper sulphate? Given that E0 = - 0.23 & E

0

= + 0.34V.

No, since nickel has negative reduction potential, it has the tendency to go as ions into solution.

14. Zinc reacts with dilute H2SO4 to give hydrogen but silver does not. Explain given

that E0 Ag+/Ag = + 0.080V and E

0 Zn2+/Zn

= - 0.76V.

Since zinc has negative reduction potential and is placed above hydrogen in electrochemical series, it liberates hydrogen but silver has positive reduction potential and is placed below hydrogen in emf series. So, Ag does not liberate hydrogen.

15. What is an electrochemical cell?

An electrochemical cell is a device used to convert chemical energy in to electrical energy. 16. What is electrochemical corrosion?

When two dissimilar metals are in contact with each other in the presence of aqueous solution or moisture wet corrosion occurs. This is otherwise known as electrochemical corrosion.

17. What is Pilling Bed worth ratio?

The ratio of the volume of oxide film formed to the volume of metal consumed is called Pilling Bed worth Ratio. 18. What is Hydrogen embrittlement?

Accumulation of hydrogen gases in the voids develops very high pressure, which causes cracks and blisters on metal. This process is called hydrogen embrittlement.

19. What isDecarburization?

Carbon content of steel decreases when heated with hydrogen. This process is called decarburization. 20. What is dry Corrosion? Give Examples (M - 14)

Dry corrosion involves direct chemical attack of the metal by atmospheric oxygen, Carbon dioxide, hydrogen

sulphide etc. Eg. (i) Tarnishing of silver in H2S gas. (ii) Action of dry HCl in iron surface. 21. Mention two differences between dry and wet corrosion?

1. Dry corrosion involves direct chemical attack of the metal by atmospheric oxygen. Wet corrosion involves setting up of tiny galvanic cells. 2. Dry corrosion follows adsorption mechanism. Wet corrosion follows electrochemical reaction mechanism.

22. What is pitting corrosion?

Pitting is a localized attack which results in the formation of a hole around which the metal is relatively unattacked.

23. What is pipe line corrosion?

Pipe line corrosion occurs when buried pipes or cables pass from one type of soil to another. Eg. From clay to sand particles. As clay is less aerated than sand particles, differential aeration corrosion takes place.

24. Zinc is readily corroded when coupled with copper than with lead. Why?

Since the difference of zinc- copper is very far as compared zinc-lead in the electrochemical series, zinc gets corroded vigorously when coupled with copper than with lead.

25. What is electroless plating? It is a technique of depositing a metal from its salt solution on a catalytically active surface of the metal to be protected by using a suitable reducing agent without using electrical energy.

26. What is electroplating?

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.

27. What is the effect of pH of the conducting medium on corrosion of metals?

Rate of corrosion is more in the acidic medium than alkaline or neutral medium. 28. What is the principle involved in impressed cathodic current method of

prevention of corrosion?

In the impressed cathodic current 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 cathode .Thus the metal is protected from corrosion.

29. Explain Galvanic corrosion with an example.

When two dissimilar metals are in contact with each other in the presence of the aqueous solution or moisture or electrolyte, the metal higher in electro chemical series undergoes corrosion. This type of corrosion is called galvanic corrosion. Eg., Zinc and Copper. Zinc actS as anode and undergoes corrosion.

30. Using chemical equation , state the mechanism of corrosion of iron in weakly

alkaline solution. Iron dissolves as Fe 2+ ions with the liberation of electrons. Fe →Fe2+ + 2 e At cathode : the liberated electrons flow from anode to cathode through metal, where the electrons are gained by

dissolved oxygen to form OH-ions. ½ O2 + H2O + 2 e → 2OH-

31. What is the effect of H2S gas when it comes in contact with iron metals? Iron reacts with H2S and liberate atomic Hydrogen.

Fe + H2S → FeS + 2 H This atomic Hydrogen diffuses ready on the metal surface and collects in the voids, where it combines to form Collections of these gases in the voids develop very high pressure which causes cracks and blisters on the metal.

32. Name two metals in which the specific volume of its oxides are greater than that

of the metals. (M - 11) Lead, Aluminium , Copper, Tin

33. What is rust? What is its chemical formula? (M - 11)

Rust is ferric oxide, Fe2O3.3H2O 34. What is concentration cell or differential aeration corrosion? Give an example.

Concentration cell type corrosion occurs when a metal is exposed to an electrolyte with varying amount of oxygen. The metal part immersed in conducting liquid or partially buried in soil is less aerated acts as anode. At anode corrosion occurs. The rest of metal part exposed to higher concentration of oxygen acts as cathode.eg Pipeline corrosion, Pitting corrosion.

PART – B (16 MARKS)

1. Describe the construction and working of a Galvanic cell. (M-03)

2.

Derive Nernst equation? What are the applications?

(M- 13, 14)

3.

What is EMF series? What are the applications?

(M-04)

4.

Explain the mechanism of chemical and electrochemical corrosion.

(M-01)

5.

What is differential aeration corrosion? Explain with four examples.

(M- 06, 14)

6.

What are the constituents of paints? Discuss the functions with examples.

(M- 08, 14)

7.

Discuss electroless plating in detail taking Ni as example.

(N- 09, 14)

8.

Explain cathodic protection in detail.

(N-06,12)

9. Write briefly about electroplating? ( N-08, M-09)

10. Discuss the factors influencing corrosion. (N-05, N-06)

11. Explain the sacrificial anode and impressed current cathodic techniques for the prevention of corrosion.

(M-07, N-14)

12. Discuss the mechanism of drying of oil paint. (N-09)

UNIT- III : ENERGY SOURCES

PART - A

1. State critical mass.

Minimum mass of a lump of uranium-235 which will undergo fission in a chain reaction is called critical mass.

2. What is a breeder reactor? A fission reactor which produces more fissionable material than is consumed in its operation is called a breeder reactor.

3. What is a nuclear chain reaction? How it is controlled?

Nuclear chain reaction is an autocatalytic reaction in which the number of neutrons keeps on multiplying rapidly till the whole of fissionable material is disintegrated. Control rods are used control and regulate the number of neutrons that can cause fission.

4. What is a battery?

A battery is a combination of electro-chemical cell connected in series. Any redox reaction occurring at an appropriate electrode can be employed to generate electricity in such cell.

5. What are primary batteries? Give an example. It is irreversible cell. Battery which cannot be recharged again by passing external electricity is called primary battery. Example: Leclanche cell, mercury cell, alkaline battery.

6. What are secondary batteries? Give an example. (M - 13)

They are reversible cells. Batteries which can be recharged again by passing external electric current are called “secondary batteries”. Ex. Ni-Cd battery, lead-acid battery and lithium battery.

7. What are the advantages of alkaline battery than dry battery?

Zinc does not dissolve in basic medium. Life is longer than dry battery, because there is no corrosion on zinc. Alkaline battery maintains its voltage (1.5V), as the current is drawn from it.

8. What are the advantages of Li battery? (M - 12)

Its cell voltage is high, 3V Lithium is a light-weight metal. Li has the more negative E° value and therefore generates a higher voltage than the other types of cells All the constituents of the battery are solids and, therefore there is no risk of leakage from the battery.

9. Write the applications of solar cells. Solar energy is made use in the electrification of rural areas of tropical region where the sunlight is effective during daytime. Solar cells are useful in refrigerator, water heater, water pump and cooker.

10. What is a fuel cell or flow battery? A fuel cell is a device in which thermal energy is directly converted to electrical energy. In a conventional system, thermal energy is converted to mechanical energy and the mechanical energy into electrical energy.

11. Write the advantages of fuel cells.

a. High efficiency of energy conservation (chemical to electrical energy) b. No emission of gases and pollutants.

12. How are anodic and cathodic electroactive materials made in Ni-Cd battery? At anode: Cadmium is oxidized to Cd2+ and further it combines with OH- ions and to form Cd(OH)2

At cathode: NiO2 gains electrons and it undergoes reduction at the cathode from +4 to +2. Ni2+ ions combine

with OH- ions to form Ni(OH)2

13. Write the uses of lead storage battery. Lead storage cell is used to supply current mainly in automobiles.

It is also used in gas engine ignition, telephone exchanges and power stations etc.

14. Write the advantages of Ni-Cd battery.

(i) It is a portable, rechargeable cell and its cell voltage is fairly constant (about 1.4 V).

(ii) It is used in electronic calculators, electronic flash units, transistors and other battery powered small tools.

15. What are the characteristics of fuel cells?

They do not store chemical energy. The efficiency of a fuel cell is about twice that of a conventional power plant for generating electricity. Fuel cell generators are free of the noise, vibration, heat transfer, thermal pollution and other problems normally associated with conventional power plants.

16. What are fissile and fertile nucleides? (M – 12 & M - 13) Fissile materials: The materials which undergo fission by slow moving neutrons are called as fissile materials. Examples: U-235, Pu-239, U-233, Pu-241. Fertile materials: The materials which do not undergo fission easily but may be made by bombardment with fast moving neutrons are called as fertile materials. Example: U-238, Th-232.

17. What are non-conventional energy sources? Give two examples. (M - 12) Renewable energy sources also called as non-conventional energy sources that are continuously replenished by natural processes. Example: solar energy, wind energy.

18. What is Nuclear fission? Give any one nuclear fission reaction. The process of breaking a heavy nucleus with a slow neutron into two lighter nuclei of almost equal size with the liberation of large amount of energy is called as nuclear fission or atomic fission.

92U235 +0n1 → [ 92U236] → 56Ba141 + 36Kr92 + 30n1 + 200.5 MeV (Energy)

19. What are the characteristics of nuclear fission process? a. Breaking of heavy nucleus by a neutron gives two or more lighter nuclei. b. The fission of each nucleus generates 2 or 3 neutrons. c. Large amount of energy is liberated during fission. d. All the fission products are radioactive, and emit beta and gamma radiations.

20. Define the term nuclear energy. The liberation of large amount of energy along with the ejection of 2 or 3 neutrons during nuclear fission reaction is called nuclear energy or atomic energy.

21. What is nuclear fusion? Give any one nuclear fusion reaction. Nuclear fusion is the process in which two or more lighter nuclei combine to form one single heavier nucleus. Eg : The combination of various isotopes of hydrogen to form helium.

1H2 + 1H3 → 2He4 + 0n1 + 17.6 MeV (Energy)

22. Distinguish between nuclear fission and nuclear fusion.

S.No. Nuclear Fission Nuclear fusion 1. A heavy nucleus splits into two nuclei Two lighter nuclei fuse together

2. Enormous amount of energy is liberated Enormous amount of energy isliberated

3. The process is possible at room temperature Process is possible only at very high temperatures

4. It is a chain process. It is not a chain process

23. What is Nuclear reactor? Nuclear reactor is a device in which nuclear fission is produced in a controlled manner to release nuclear energy. The main purpose of a reactor is to produce electrical power. In nuclear reactors , the heat generated during fission is used to produce steam. The steam is used to drive the turbines which produce electricity.

24. What are advantages of nuclear power generation? Nuclear power generation emits relatively lower amounts of green house gases. It is possible to generate a high amount of electrical energy in one single plant.

25. Explain the function of control rods? Control rods absorb neutrons and regulate the number of neutrons that can cause fission. Eg: Boron ,Cadmium.

26. Compare light water reactor and breeder reactor?

S.No. Light water reactor Breeder reactor 1.

Fissile materials like U235 are used as fuel

Fertile materials like U238 is used as fuel

2. During fission, no radioactive emission occurs During fission, gamma and beta emission occurs.

3. Moderators are used to slow down the neutrons Moderators are not used

4. Light water is used as coolant Liquid sodium is used as coolant

27. Explain charging and discharging characteristics of a battery? Discharging is an electrochemical process by which a battery delivers current to an external circuit at an cost of the consumption of electrode materials. Charging is an electrolytic process by which a constant current is passed through a battery in order to regenerate the active materials back into their original form.

28. What are the advantages of storage batteries?

The secondary batteries have advantages over the primary batteries in that the net cell reaction can be reversed during the charging process and the current can be drawn during the discharge process.

Storage batteries have better cycle life and capacity, so that it can be used over and over again.

PART – B (16 MARKS)

( M-06, N-06)

1.

Write note on Ni-Cd battery.

2.

Explain the construction and working of Lead acid battery.

(M-10, N-14)

3.

Write short note on wind energy.

(M-09)

4.

Describe the construction and working of H-O fuel cell.

(M-10, N-10)

5.

State the principle and applications of photo voltaic cell.

(M-10)

6.

What is nuclear reactor? Explain the various components of light water nuclear power

plant with a suitable block diagram. (M-10)

7. What is breeder reactor? Explain with an example (M-10, N-14)

8. Explain the construction and working of alkaline battery.

9. Write notes on Li Battery.

10. Explain the following with example.

(i) Nuclear

fission (ii) nuclear fusion (iii) Nuclear energy (M-07)

11. Describe the components of light water nuclear power plant with a neat block diagram. (M-05, 09)

12. Explain the working of nuclear reactor with diagram. (M-10, 14)

13. Discuss the construction and working of Ni-Cd battery.

14. What are lead accumulators? Explain the construction and functioning of a lead accumulator. (M-14)

15. Describe the principle behind the functioning of solar cells. (N-14)

UNIT – IV : ENGINEERING MATERIALS

PART – A (2 MARKS)

1. What are abrasives? Give two examples each for Natural and Artificial abrasives. Abrasives are hard substances, used for polishing, shaping, grinding operations. They are characterized by high melting point, high hardness and chemically inactive. Example: Natural abrasives – Diamond, Emery Synthetic abrasives – Silicon carbide, Boron carbide.

2. What is Moh‟s scale? Name the hardest substance known. Moh‟s scale is a scale, in which common abrasives are arranged in the order of increasing hardness. The hardest material is Diamond and its Moh‟s scale is 10.

3. What are called soft abrasives? Abrasives having their hardness 1- 4 in Moh‟s scale are known as soft abrasives. Example: Talc, Gypsum.

4. What isCorundum? Corundum is crystalline aluminum oxide (Al2O3).Its hardness is 9 in Moh„s scale. It is used in grinding wheels and glasses.

5. How is silicon carbide or carborundum prepared? It is prepared by heating a mixture of silica (60%) and carbon (40%) with saw dust and a little salt in an electric furnace to about temperature 1500oC. SiO2 + 3C → SiC+ 2CO↑ ΔH=+478.7KJ

6. How is Boron carbide prepared? It is prepared by heating a mixture of Boron oxide (B2O3) and coke (carbon) in an electric furnace to about 2200oC.

2B2O3 + 7C → B4C + 6CO↑

7. Arrange norbide, carborundum, corundum, garnet increasing order of hardness? Garnet < Norbide < Corundum < Carborundum.

8. Mention some important applications of abrasives. (i) To clean the surface prior to coating abrasive powders are used. Example: Quartz,Garnet. (ii) To prepare smooth wood, metal and plastic surfaces, abrasive paper is used. Example: Alumina,

siliconcarbide. (iii) To remove the scales from iron surfaces, grinding wheels are used.

9. What is emery? It is finely grained opaque massive mineral dark-grey to black in Colour. It consists of 55-75% crystalline alumina, 20-40%magnetite and 12% other mineral of which the major part is tourmaline.

10. What are refractories?

Materials that can withstand high temperature without Softening or undergoing any deformation in shape are called refractories.

Example: Silicon carbide, Zirconia

11. Mention any three characteristics of good refractories.

(i) It should be infusible at high operating temperatures. (ii) It should be chemically inert towards corrosive gases, metallic slags and liquids produced in the furnaces. (iii) It should resist the abrading action of flue gases, flames etc. (iv) It should have high refractoriness.

12. What is meant by refractoriness of a refractory? It is the temperature withstanding capacity of a material. It refers the ability of a material to withstand very high temperature without softening or deformation under particular service conditions.

13. What is meant by pyrometric cone equivalent of a refractory? It is the number which indicates the softening temperature of a particular refractory specimen with standard dimensions(38mm height, and 19mm triangular base) and composition. Silica bricks -PCE number 32, Alumina bricks - PCE number 37.

14. What is thermal spalling? How is it minimized? It is the property of breaking or cracking or peeling off a refractory material under high temperature, especially when there is a sudden change in temperature. Thermal spalling is due to rapid change in temperature and also due to slag penetration. It can be minimized by two ways. i) By avoiding sudden changes in temperature. ii) By using high porosity, low coefficient of expansion and good thermal conductivity refractory.

15. What are the important properties of high alumina bricks? Alumina bricks possess very low coefficient of expansion, high porosity, high temperature load- bearing capacity.

16. What is meant by dimensional stability? (M - 14) It is defined as the stability of a refractory in its dimension when it is heated to high temperature over a prolonged time. The dimensional stability of a material should be high. It may be reversible or irreversible.

17. Define porosity of a refractory. Porosity of a refractory material is given by the ratio of its pores volume to that of its bulkvolume. Porosity (P)=W-D X 100

W-A Where W= Weight of saturated specimen (with water) in air.

D= Weight of dry specimen A= Weight of saturated specimen (with water) in water.

18. What are the raw materials used for the manufacture of cement. Calcareous materials, CaO (limestone) Argillaceous materials, Al2O3 and SiO2 (clay) Powdered coal or fuel oil Gypsum (CaSO4. 2H2O)

19. Give the appropriate composition of Portland cement. Dicalcium silicate = 25%

Tricalcium silicate = 45%

Tricalcium aluminate = 10%

Tetracalcium alumino ferrite = 9%

Rest = CaO + MgO + CaSO4

20. What is meant by flash set? When the cement is mixed with water, at first, hydration of tricalcium aluminate (C3A) takes place rapidly (within 1 day), and the paste becomes quite rigid within a short time which is known as initial set or flash set.

21. Why should we do not paint the freshly plastered cement surface? Because it blocks the pores or capillaries present on the surface and prevents hydration of C3S and C2S which are responsible for development of compressive strength of cement.

22. Define the term “setting” and “hardening” of cement. Setting: It is defined as the stiffening of the original plastic mass, due to the formation of tobermonite gel. Hardening: It is defined as the development of strength due to formation of crystals.

23. What is the difference between setting and hardening of lime and cement?

Setting and hardening of lime involves dehydration and carbonation reaction.

Ca(OH)2 + CO2 → CaCO3 + H2O

CaO+CO2 → CaCO3

Setting and hardening of cement is mainly due to hydration and hydrolysis reaction of Bogue compounds with water.

24. What are components of water proof cement? (M - 14) Water proof cement consists of portland cement clinker with an additive like sodium oleate, Calcium stearate, aluminium stearate etc. (0.1 – 0.5% by weight).

25. Define the glass? Glass is an amorphous, hard, brittle and transparent or translucent, super-cooled liquid, obtained by fusing a mixture of a number of metallic silicates. Most commonly silicates of Na, Ca and Pb are used. It possesses no sharp melting- point, crystalline structure and definite formal.

26. What are general properties of glasses? (i) It is amorphous. (ii) It has no definite melting-point. (iii) It is very brittle. (iv) It softens on heating. (iv) It is affected by alkalis.

27. Give the composition, properties and uses of hard glass. Composition: The approximate composition is K2O.CaO.6SiO2

Properties: Potash-lime possess high melting point, so it will not fuse easily. It is less acted upon by acids, alkali and other solvents than ordinary glasses.

Uses:

These glasses are used for manufacturing combustion tubes, chemical apparatus, etc.

28. What are the important uses of Glass wool? It is used for electrical and sound insulation. It is used in filtration of corrosive liquids like acids. It is also used for manufacturing fibre-glass, by blending with plastic resins.

PART – B (16 MARKS)

1. Explain the synthetic and natural abrasives. (M-09)

2. Describe the classification of abrasives with suitable examples. Explain Mohr‟s scale of hardness. (M-14)

3. Explain in detail the properties of refractories. N-06)

4. What are the classifications of refractories? (N-04, M-10)

5. What are the raw materials used for the manufacture of cement? Describe the manufacture of cement by wet

process. (N-03)

6. Explain the manufacture and important properties of alumina bricks and carborundum. (M-03, M-14) 7. Explain setting and hardening of cements with the reactions involved. (M- 03, 14)

8. What is glass? Explain the sequential steps involved in the manufacture of glass. (M-14)

9. List out the general properties of glass. Write the composition, properties and uses of soda and flint

glasses. (M-03)

UNIT – V : FUELS AND COMBUSTION

PART - A

1. What is gross calorific value (GCV)? Gross calorific value is the total heat generated when a unit quantity of fuel is completely burnt and the products of combustion are cooled to room temperature.

2. What is Net calorific value (NCV)?

The net heat produced when a unit quantity of fuel is completely burnt and the products of combustion are allowed to escape. NCV = GCV – Latent heat of condensation of steam produced.

3. Name the various determinations of proximate analysis.

It involves the determination of percentage of a. Moisture content b. Volatile matter c. Ash content d. Fixed carbon in coal.

4. What is the significance of volatile matter in coal?

High percentage of volatile matter is undesirable because i. It reduces the calorific value of coal ii. It has low ignition temperature. iii. It burns with a long yellow smokes flame.

5. Distinguish between proximate and ultimate analysis.

S.No Proximate analysis Ultimate analysis

1

It involves the determination of physical constituents like moisture, volatile, ash and fixed carbon contents incoal

It involves the determination of chemical constituents like carbon, hydrogen, nitrogen and sulphur and oxygen contents in coal

2 It gives the approximate composition of the main constituents of coal

It gives the exact composition of the elementary constituents of coal.

6. Why coke is superior as a metallurgical fuel? (M - 13) a. Coke is stronger and more porous than coal. b. By coking, much of undesirable sulphur is removed c. Coke does not contain much volatile matter than coal. d. Coke burns with a small flame and without smoke.

7. Define octane number of petrol? How can it be improved? The octane number is defined as the percentage of iso-octane present in a mixture of iso-octane and n- heptane. Improving the octane number of a fuel by a. The addition of anti- knock compounds like TEL. b. Low octane petrol is blended with high octane compounds like alcohol (straight – run petrol is mixed with reformed petrol, benzol and alcohol).

8. What is meant by carbonization of coal?

When coal is heated strongly in the absence of air, it is converted into a substance of lustrous, dense, porous, coherent mass called coke. The process of preparing coke from coal is known as carbonization of coal.

9. What are Caking coals and coking coals?

When coals are heated strongly, the mass becomes soft, plastic and fuses to give a coherent mass. Such types of coals are called Caking Coals. But if the mass so produced is hard, porous and strong then the coals are called Coking Coals.

10. What is meant by hydrogenation of coal?

If coal is heated with hydrogen under high pressure, it is converted into gasoline. This method of preparing liquid fuels from solid coal is called hydrogenation of coal.

11. What is knocking? (M - 13)

Knocking is a kind of explosion occurs in IC engines due to sudden increase of pressure developed by spontaneous combustion of fuel and air mixture.

12. Explain the chemical structure and knocking.

The knocking tendency of fuel hydrocarbons mainly depends on their chemical structures. The knocking tendency decreases in the following order. Straight chain paraffins > Branched chain Paraffins > Cycloparaffins > Olefins > Aromatics. Thus olefins of the same carbon chain length possess better anti knock properties than the corresponding paraffins.

13. Why should leaded petrol not to be used?

Lead deposits on the spark plug and on cylinder walls, which is harmful to engine life and this creates atmospheric pollution.

14. Define cetane number / How are diesel oil rated? How are they improved?/

How can cetane number of a fuel be improved?

The cetane number is defined as "the percentage of hexa decane present in a mixture of hexa decane and α- methyl naphthalene, which has the same ignition lag as the fuel under test".

Cetane number improvement:

The cetane number of diesel oil can be increased by adding additives called dopes. Important dopes: Ethyl nitrate, Iso-amyl nitrate.

15. What is the action of TEL in internal combustion engines?

Tetra ethyl lead is converted into finely divided lead oxide particle in the cylinder and these particles react with any hydrocarbon peroxide molecules formed, thereby slowing down the chain oxidation reaction and thus decreasing the chances of early detonation.

16. List out the advantages of gaseous fuels over solid and liquid fuels.

Gaseous fuels can flow through pipes and hence can be easily transported to the place of need. It can be lighted at a moment‟s notice. It burn with high efficiency and a high temperature flame is obtained in no time. It does not produce any smoke and ash and it burns freely in the presence of air.

17. What is the drawback of presence of sulphur in the coal? (M - 09)

The harmful gases SO2 and SO3 will create air pollution. Sulphur containing coal is not suitable for the manufacture of metallurgical coke.

18. How is water gas superior to producer gas? (N - 09)

It‟s calorific value is higher than producer gas. It has very less amount of N2 than producer gas. It is used for the manufacturing of power alcohol.

19. Distinguish between coal and coke. (M - 10)

S.No Coal Coke 1. It possesses lower strength and

porosity It possesses porosity

higher strength and

2. It is a natural fuel It is a secondary fuel

20. What are the advantages of CNG? (M - 10) o CNG is a much safer fuel, since it ignites at a higher temperature than gasoline and diesel. o Combustion of CNG leads to lesser Carbon mono oxide emissions than gasoline. o CNG mixes with air than liquid fuels.

21. Mention any two disadvantages of LPG over other gaseous fuels. (M - 11)

Needs little care for maintenance Flexibility and easy control Easy to manipulate Comparatively, less health hazard, even in case of leakage.

22. Write down the composition of producer gas. (M- 11 & M - 13)

Producer gas is mixture of carbon monoxide, hydrogen and nitrogen. The average composition of producer

gas is : CO = 30%, H2 = 12%, N2 = 55% & CO2 = 3%

23. What do you mean by ignition temperature? It is defined as the lowest temperature to which the fuel must be heated, so that it starts burning smoothly. In the case of liquid fuels, the ignition temperature is called flash point.

24. What is bio-diesel? Vegetable oils comprise of 90-95% triglycerides with small amount of diglycerides, free fatty acids, phospholipids etc. are known as bio-diesel. The viscosities of vegetable oils are higher and their molecular weights are in the range of 600-900 which are about three times higher than those of the diesel fuels.

25. What do you mean by power alcohol?

When ethyl alcohol is blended with petrol at concentration of 5-10%, it is called power alcohol. In other words absolute alcohol (100% ethyl alcohol) is also called as power alcohol. Addition of ethyl alcohol to petrol increases its octane number.

PART – B (16 MARKS)

1. Describe proximate analysis. What is the significance of it? (M-05, N-05, N-06, M-09)

2.

Bring out the importance of ultimate analysis.

(N-09, M-14) 3. In what ways Otto Hoffmann method is advantageous than the traditional method. Explain the various products

and the recovery process.

(M-08, N-12)

4.

Explain the synthesis of petrol by Bergius process.

(M- 09, 14)

5.

What is Water gas? How is it manufactured?

(M-05, N-06)

6.

How is producer gas manufactured? Give its composition and uses.

7.

Write a brief note on CNG and LPG.

(N-09)

8.

How is flue gas analysed using Orsat‟s apparatus? Give suitable diagram.

(M-14)