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KNOWLEDGE INSTITUTE OF TECNOLOGY, SALEM

CY 8151- ENGINEERING CHEMISTRY

PART A WITH ANSWERS

UNIT-I: WATER AND ITS TREATMENT

1. Why is water softened before using in boiler? Or Mention any two disadvantages of deposits in

boilers.

If hard water obtained from natural sources is fed directly into the boilers, the following troubles

may arise.

Scale and sludge formation

Priming and foaming[carry over]

Boiler corrosion.

2. What are scale and sludges?

Scale:

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 MgCl2.

Sludges:

If the precipitate is loose and slimy it is called as sludge. Sludges are formed by

substances like MgCl2, MgCO3, MgSO4 and CaCl2.they have greater stability in hot water than

cold water

3. What are the disadvantages of scale formation?

Scales act as thermal insulators.it decreases the efficiency of boiler. Any crack developed on the

scale, leads to explosion.

4. What are the requisites of drinking and boiler feed water?

Boiler waterMust have zero hardness and free from dissolved gases like oxygen and

carbon di oxide.

Drinking waterpH=7 to 8.5

Total hardness and dissolved solids of water should be less than 500 ppm

5. Define softening of water. How is it carried out?

The process of removing hardness producing salts from water is known as softening or

conditioning of water.it can be done by

External treatment

Internal treatment

6. Soft water is not DM water whereas DM water is soft water-justify [or]distinguish between soft

and demineralized water.[2013]

DEPT. OF CHEMISTRY, KNOWLEDGE INSTITUTE OF TECNOLOGY 1



PART A WITH ANSWERS

The soft water produced by lime soda and zeolite process, does not contain hardness producing

Ca2+ and Mg 2+ ions ,but it will contain other ions like Na+,K+,Cl+etc.,on the other hand DM water does

not contain both anions and cations.

7. How is exhausted resin regenerated in ion-exchange process?

When the cation exchange resin is exhausted, it can be regenerated by passing a solution of

dilute HCl or H2SO4.

RCa +2HCl …… RH2 +CaCl2

RNa + HCl …… RH +NaCl

When the anion exchange resin is exhausted, it can be regenerated by passing a solution of dilute

NaOH.

R’Cl2 + 2NaOH……… R’(OH)2 +2NaCl.

8. How is water demineralized in ion exchanger?

When the water containing [both anions and cations] are passed through ion exchange columns,

it absorbs all the ions as shown below

Cation exchanger: RH2 +CaCl2 RCa +2HCl

Anion exchanger: R(OH)2 +2HCl RCl2 +2 H2O

9. What is colloidal conditioning?

In low pressure boilers, scale formation can be avoided by adding organic substances like

kerosene, tannin, gelatin, agar-agar gel etc., They get coated over the scale forming precipitates, thereby

yielding non sticky and loose deposits. These can be removed by predetermined blow down operation.

10. How is sodium aluminate conditioning?

Sodium aluminate added to the boiler water gets hydrolyzed, yielding sodium hydroxide and a

gelatinous precipitate of aluminium hydroxide as in the reaction.

NaAlO2 + 2H2O NaOH + Al(OH)2

The sodium hydroxide so formed, precipitates some of the magnesium ion of hard water as magnesium

hydroxide.

MgCl2 + 2NaOH 2NaCl + Mg(OH)2

The flocculent precipitates of Al(OH)2and Mg(OH)2 , produced inside the boiler, entrap finely suspended

and colloidal impurities including oil drops and silica. It can be removed by blow down operation.

11. What is phosphate conditioning? [Or] What is the role of phosphates in the internal treatment of

water?

Scale formation can be avoided by adding sodium phosphate.it is used in high pressure boilers.

The phosphates react with Ca2+ and Mg 2+ salts to give soft sludge of calcium and magnesium

phosphates.




PART A WITH ANSWERS

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

12. What are boiler compounds? Mention two different boiler compounds and their actions.

Scale forming substances can be removed by adding chemicals directly to the boiler. These

chemicals are called boiler compounds.

Examples

Sodium carbonate and sodium phosphate

CaSO4+ Na2CO3 CaCO3 +Na2SO4

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

13. What is calgon conditioning? How is it functioning in water treatment?

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.

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

14. Write the principle involved in the desalination of water by reverse osmosis. [Or]what is meant by

RO ? How is applied in the desalination of water?

If pressure in the excess of osmotic pressure is applied on the higher concentration side, the

solvent flow is reversed ie.,solvent flows from higher concentration to lower concentration. This process

is called reverse osmosis.

15. Define desalination.

The process of removing common salt [sodium chloride]from the water is known as

desalination. The water containing dissolved salts with peculiar salty or brackish taste is called brackish

water.

16. Name some of the membranes employed in reverse osmosis process. State the advantages of this

process.

Cellulose acetate, cellulose butyrate.Advantages

It removes ionic as well as non-ionic, colloidal impurities. The life time of the membrane is high and it can be replaced within few minutes

17. What is blow down operation?Blow-down operation is a process of removing a portion of concentrated water by fresh water

frequently from the boiler during steam production.

18. What is meant by priming and foaming? How can they be prevented?Priming is the process of production of wet steam. Priming can be prevented by controlling the

velocity of steam and keeping the water level lower.Foaming is the formation of stable bubbles above the surface of water. Foaming can be

prevented by adding coagulants like sodium aluminate and antifoaming agents like synthetic polyamides.




PART A WITH ANSWERS

19. What is meant by caustic embrittlement? how is it prevented?Caustic embrittlement means intercrystalline cracking of boiler metal.Prevention

Using sodium phosphate as softening agent instead of sodium carbonate. By adding tannin, lignin to the boiler water, which blocks the hair cracks.

UNIT-II: SURFACE CHEMISTRY AND CATALYSIS

1. Define adsorbate & adsorbent ?Adsorbate :

The substance which is held on the surface of the solid is called adsorbate.Adsorbent :

The solid that takes up a gas (or) a solute from the solution is called adsorbent.Ex: Ammonia – Adsorbate , charcoal – adsorbent

2. Differences b/w Adsorption & Absorption ?

s.no Adsorption Absorption

1. Adsorption is a surface phenomenon.

It is a bulk phenomenon.

2. It is a rapid process. It is a slow process

3. Equilibrium is attained easily. Equilibrium is abtained slowly.

3. Define physical Adsorption (or) physisorption chemical adsorption?Physical Adsorption :

It is the one, in which the absorbed molecules are held together by means of weak Vander Waal’s forces of attraction.EX: Adsorption of H2 on charcoal.Chemical Adsorption :

It is one in which the absorbed molecules are held together by means of strong chemical bonds. It may be covalent (or) ionic. EX : Adsorption of H2 on Ni.

4. What is the effect of increases in temperature & pressure on the adsoption of gases on charcoal?Pressure :

If the pressure is increases , physisorption is increases but chemisorptions is decreases.Temperature :

If the temperature is increases, physisorption is decreases but chemisorptions is increases and decreases.

5. Adsorption isotherm . define ?




PART A WITH ANSWERS

It is a relationship between magnitude of Adsorption with pressure, at constant temperature. Mathematically represent that X/m = KP1/n

6. What are the limitation of freundlich’s Adsorption isotherm? This equation is purely empirical. There is no theoretical evidence. This equation only valid at low pressure. It is invalid at higher pressure. This equation only valid at low concentration of liquid. But invalid at higher

concentration. K and n value are very with temperayure.

7. Define freundlich’s Adsorption isotherm?It is a relationship between magnitude of adsorption with pressure of gases (or)

concentration of liquid at constant temperature. X/m = KP1/n

8. Write the postulates (or) Assumptions of Langmuir’s adsorption isotherm?Assumption :

It is a mono molecular adsorption. Heat of adsorption is same for all sites. Different site do not interact with each other. That is no interaction between the

adjacent adsorbed molecules. There is dynamic equilibrium exist between adsorption and desorption of the

molecules.

9. Write the application of activated carbon? It is used in gas masks. Which absorb all toxic gases. It is used for removing coloring matter from the sugar solution. It is also used for air – conditioning systems.

10. Explain how the finely divided state of catalyst is more efficient than bulk phase?When the fineness of the catalyst increases. It also increase with free valencies (or)

active centres. Which are responsible for the adsorption increases.

11. Action of promoters?The substance which increase the activity of a catalyst

In here Mo act as a promoters.

12. What is catalyst poison? Explain its action?The substance which destroys the activity of a catalyst. It is called catalytic

poison.Carbonyl group act as a catalytic poison.

13. Write any four application of adsorption process?Activated charcoal: It is used for gas masks. Which adsorb all toxic gases.Silica & Alumina gels:

It is used as absorbent for removing moisture from 800mDEPT. OF CHEMISTRY, KNOWLEDGE INSTITUTE OF TECNOLOGY 5



PART A WITH ANSWERS

It is used ion – exchange water softening method Absorption process used for arsenic poisoning & dying industry

14. Define catalyst.It is a susbstance which alters the rate of achemical reaction,itself remaining

chemically unchanged at the reaction. 15. What are the types of catalysis?

There are two types of catalystis.They are Homogeneous catalysis Heterogenous catalysis

16. What is homogeneous catalysis?Give example.In Homogeneous catalysis, the catalyst is in the same phase as the reactants and

is evenly distributed throughout.Example.Hydrolysis of sucrose in aqueous solution in the presence of mineral acid

Catalyst17. What is heterogeneous catalysis?

In a heterogeneous reaction, the catalyst is in a different phase from the reactants.

Examples of heterogeneous catalysis

The hydrogenation of a carbon-carbon double bond

The simplest example of this is the reaction between ethene and hydrogen in the presence of a nickel catalyst.

18. Write any few criteria for catalysis.

Characteristics of Catalysts are as follows:

1. The catalyst remains unchanged (in mass and chemical composition ) in the reaction (Activity of catalyst.)

2. A small quantity of the catalyst is required. e.g. One mole of colloid Pt catalyses

3. The catalyst does not change the equilibrium constant. But the equilibrium approaches earlier.

4. Specificity of Catalyst

19. Define autocatalysis. Give egIn certain reactions, one of the product acts as a catalyst. In the initial stages the reaction

is slow but as soon as the products come into existences the reaction rate increases. This type of phenomenon is known as auto-catalysis. hydrogenation of ethyl acetate




PART A WITH ANSWERS

CH3COOCH2CH3 + H2O- CH3CH2OH + CH3COOH

20. What is the difference between a homogenous and heterogeneous catalysis? Catalysts can be divided into two main types - heterogeneous and homogeneous. In a

heterogeneous reaction, the catalyst is in a different phase from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants.

21. What is catalytic converter?A catalytic converter is an emissions control device that converts toxic gases and

pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction.

22. What is Enzyme catalysis? Enzyme catalysis is the increase in the rate of a chemical reaction by the enzyme(active site of a protein).

23. List out the characteristics of enzyme catalysis. Enzymes are highy specific. At higher temperatures the rate of the reaction is faster. The rate of the reaction invovlving an enzyme is high at the optimum

temperature. Enzymes have an optimum pH range within which the enzymes function

is at its peak. Enzymes are marketly poisoned.

24. Define turn over number.In turnover number is defined as the number of molecules converted into products in unit

time by one molecule of enzyme .

UNIT III: ALLOYS AND PHASE RULE

Write the number of phases and components in the following heterogeneous system? CuSO4 (s) + 5H2O (l) CuSO4. 5H2O(s)

Phase =3 (Solid CuSO4, Solid CuSO4.5H2O. liquid 5H2O)Component = 2 (CuSO4, H2O)Degree of freedom = F = C-P+2F = 2-3+2 F = 1 univariant system

2. Give any two uses of each brass and bronze? Brass:

It is used for making of Jewellery It is used for making of hardware It is used for making of house hold materials

Bronze: It is used for making of jewellery It is used for making of coins, statues


https://en.wikipedia.org/wiki/Enzyme

https://en.wikipedia.org/wiki/Water_(molecule)



PART A WITH ANSWERS

It is used for foundry works

3. What is condensed phase rule? F = C – P + 1In solid – liquid of an alloy has no gaseous phase. So the effect of pressure is negligible. Since the pressure is kept constant. This above equation is called reduced phase (or) condensed phase rule.

4. What is Alnico? This is an alloy of Al, Ni, and Co Al = 12% Ni = 28% Co = 35 % Fe = 20%

It is highly magnetic and used for making powerful magnets It is used for generators, motors, telephone

5. Calculate the number of phases and component present in the following system? (a) NH4Cl(S) NH3 (g) + HCl (g)

Phase=2 (solid NH4Cl, gas mixture NH3, HCl)Component =1 (NH4Cl)Degree of freedom = F = C-P +2 → 1-2+2 F = 1 uni variant system

(b) An emulsion of oil in water Oil water Phase=2 (oil, water), Component=1(oil, water)Degree of freedom = F = C-P+2 =2-2+2 F = 2 bivariant system(c) MgCO3(S) MgO(S) + CO2(g) (or) CaCO3 (s) CaO(s) + CO2g)

Phase=3(Solid caco3, solid Cao, gas CO2 )Component=2 (solid CaCO3 & solid CaO)Degree of freedom F = C – P + 2 = 2-3+2 F = 1 Univariant system 6. Give the composition and uses of Nichrome? Nichrome is an alloy of nickel and chromium Its composition is Ni = 60% Cr = 12% Fe = 26% Mn = 2%

It is used for making of boilers, machineries It is used for making of household electrical materials It is widely used for making resistance coils, stoves.

7. Mention any five purpose of making alloys? Increase the hardness of the metal Decrease the melting points of the metal To resist the corrosion of the metal To modify chemical activity of the metal To modify the colour of the metal

8. Define phase? Give examples? Phase is defined as any homogeneous physically different portion and mechanically separable portion. That can be separated from other parts by definite boundaries. Ice(S) water (l) water vapour (g) Phase = 3




PART A WITH ANSWERS

9. Define component? Give examples? Component is defined as the some number of independent chemical constitutions. The composition of each phase can be expressed interms of chemical equation. Ice(S) water (l) water vapour (g) C = 1 All the phase expressed in term of chemical equation = H2O. So this system is called one component system.

10. Define degree of freedom? (May/June-16) Degree of freedom is defined as the minimum number of independent variable such as temperature, pressure and composition. It must be order to define the system completely. F = C – P +2 Water water vapour C = 1, P = 2 F = 1 – 2 +2 F = 1 univariant system11. Define phase rule? F = C – P + 2 It is the relationship between the number of degree of freedom, component, and phase.

12. What is stainless steel? These are alloy, steels containing chromium together with other elements. Such as Ni, Mo. Cr = 16% and carbon content = 0.3 -1.5 %13. What is a solder? These are low melting alloys of tin and lead

It have low melting point It is used for electrical and electronic applications and used for soldering steel joints.

E.g: silver soft solder14. What is heat treatment of alloys? Heat treatment is defined as “The process of heating and cooling of solid steel material under controlled conditions. During heat treatment certain physical properties are changed but without changing its chemical composition.15. What is hardening of steel? Mention its purpose? It is the process of heating steel beyond the critical temperature and then suddenly cooling it either oil or salt water or some other fluid. Hardening increases the hardness of steel.Purpose:

It increases its resistance to wear, ability to cut other metals and strength It increase abrasion resistance.

15. Define melting point, Eutectic and Triple point?Melting pointPure, crystalline solids have a characteristic melting point, the temperature at which the solid melts to become a liquid. The transition between the solid and the liquid is so sharp for small samples of a pure substance that melting points can be measured to 0.1oC. The melting point of solid oxygen, for example, is -218.4oC.Eutectic pointThe point in a phase diagram indicating the chemical composition and temperature corresponding to the lowest melting point of a mixture of components.Triple pointThe three curves OA, OB and OC meet at a single point ‘O’, where three phases namely solid, liquid and vapour are simultaneously at equilibrium. F = C − P + 2; F = 1 − 3 + 2; F = 0

16. What are alloys?DEPT. OF CHEMISTRY, KNOWLEDGE INSTITUTE OF TECNOLOGY 9

https://en.wiktionary.org/wiki/melting_point

https://en.wiktionary.org/wiki/phase_diagram



PART A WITH ANSWERS

An alloy is defined as “ homogeneous solid solution of two or more different elements, one of which at least is essentially a metal”.Eg. Alnico, Brass, Bronze, Stainless steel etc.,

17. What is triple point?It is the temperature at which three phases are in equilibrium.

Ice(S) water (l) water vapour (g)

18. What is the degree of freedom at eutectic point in Lead- Silver system? Phase-3 Component-2 F = C-P+1 = 2-3+1 = 0 System is non-variant F = 0

20. What is hardening of steel? Mention its purpose. It is the process of heating steel beyond the critical temperature and then suddenly cooling it either in oil or brine-water or some other fluid.Objectives (or) Purpose of Heat treatment

Improvement in magnetic and electrical property Removal of the imprisoned trapped gases.Removal of internal stresses.Improve corrosion resistance

UNIT IV: FUELS AND COMBUSTION1. What is the drawback of sulphur present in the coal?

The combustion products of sulphur. That is so2 and so3 are harmful and have corrosion

effects on equipments.

The coal containing sulphur is not suitable for the preparation of metallurgical coke.

It affects the properties of the metal.

2. Define cetane number. How can it be improved?

Thus the cetane number is defined as the percentage of hexa decane present in a mixture of

hexa decane and 2- methyl naphthalene.

CH3-(CH2)14-CH3

Hexa decane ( Cetane Number = 100.)

The cetane number of diesel oil can be increased by adding certain chemicals like ethyl nitrate.

3. What is CNG? Give its composition and uses? (2017)

CNG- Compressed Natural Gas

Constituents Percentage%

Methane 88.5

Ethane 5.5

Propane 3.7




PART A WITH ANSWERS

Butane 1.8

Pentae 0.5

Uses:

CNG is the cheapest

It is less expensive than petrol and diesel

It produce less co and hydrocarbon

It is used to run an automobile vehicle like bus, car, auto

4. Write down the composition and uses of producer gas?

It is a mixture of Co & N2 with small

Co = 30 % , N2 = 51 – 56 % , H2 = 10 – 15 %

Its calorific value is about 1300 kcal/m3

USES:

It is used for heating furnaces

It is used for industrial purpose & It is used for reducing agent

5. Write down the composition and uses of water gas?

It is a mixture of Co & H2 with small amount of N2.

Co = 41% H2 = 51% N2 = 4% Co2 +CH4 = Rest

Its calorific value is about 2800 kcal/m3

USES:

It is used for production of H2

It is used for synthetic petrol in this Cher tropsch process

It is used for manufacture of alcohol.

6. Define octane number? How can it be improved?

Octane number is defined as the percentage of iso –octane present in a mixture of iso - octane

and n- heptane.

CH3

CH3

CH – CH2 – C –CH3 CH3 – (CH2)5 – CH3

CH3

CH3

The octane number of petrol can be increased by adding certain substances like TEL,

aromatic phosphates.




PART A WITH ANSWERS

7. Distinguish b/w proximate and ultimate analysis of coal? (2017)

8. What are the different varieties of coal? (or) Write briefly on the ranking of coal?

Coal is classified on the basis of its rank. The rank of coal indicates its degree of maturity.

Wood Peat Lignite Bituminous Anthracite

50%C 57%C 67%C Coal 83%C 93%C

9. Give the characteristics of metallurgical coke?

1) Purity : Moisture, ash, sulphur contents should be low.

2) Porosity : Coke should be highly porous

3) Strength : It should be high mechanical strength

4) Calorific value : Coke should be high calorific value.

10. What are the advantages of Otto- Hoff man’s s method?

Increase the thermal efficiency of the carbonization process

Recover the valuable by products like coal gas ammonia, naphthalene, benzene etc.

11. Define knocking?

Knocking is a kind of explosion due to rapid pressure rise occurring in an internal combustion engine. It

produced unwanted sounds in engine.

12. What is leaded petrol? Give its significance in automobile?

When the petrol is mixed with tetra – ethyl lead (TEL) it is called leaded petrol.

Significance:

Knocking in petrol engine is minimized.

13. What are the advantages of LPG?

It is used for domestic and industrial purpose.

DEPT. OF CHEMISTRY, KNOWLEDGE INSTITUTE OF TECNOLOGY

Proximate Analysis Ultimate Analysis

It involves the determinations

of physical constituents like

moisture, volatile, ash

contents in coal.

It involves the determination

of chemical constituents like

carbon, Hydrogen, Nitrogen,

Sulphur contents in coal.

It gives the approximate

composition of the main

constituents of coal.

It gives the exact

composition of the

elementary constituents of

coal.

12



PART A WITH ANSWERS

It have high calorific value

It emit less amount of co and hydrocarbon

It burns completely without any residue

Storage and handling is very easy.

14. Define calorific value.

The calorific value of a fuel is defined as the total amount of heat librated, when a unit mass of fuel is

burnt completely. Heat can be pleasured in terms of calorie, kilocalorie.

15. Calculate the GCV and NCV of coal having?

C = 85%, H = 8%, N =2%, Ash = 4% ?

Solution:

% 0 = 100 –[%C+%H+%S+%N+%ash] = 100-100 = 0

Gross calorific value = 1/100[8080x%C+34500[%H-%0/3]+2240x%S]K.cal/kg

Net calorific value = GCV-9/100Hx587k.cal/kg

=1/100[8080x85+34500[8-0/8]+2240]kcal/kg

=1/100[965040] kcal/kg

GCV=9650.4kcal/kg

NCV=9650.4-9/100x8x857 kcal/kg

=9650.4-422.64 NCV=9227.76 kcal/kg

UNIT V: ENERGY SOURCES AND STORAGE DEVICES1. Define nuclear fission. Give an example.

Nuclear fission is defined as “the process of splitting of heavier nucleus into two (or) more smaller nuclei with simultaneous liberation of energy.” 92U235 + 0n1 → [92U236] → 56 Ba140 + 36Kr 93 +3 0n1

2. Give some characteristics of nuclear fission.

i. A heavy nucleus when bombarded by slow moving neutrons, split into two or more nuclei.

ii. Two or more neutrons are produced fission of each nucleus.

iii. All the fission fragments are radioactive, giving off β and γ-radiations.

iv. The atomic weights of fission products range from about 70 to 160.

3. What is nuclear fusion? Give an example.

The process of combination of lighter nuclei into heavier nuclei, with simultaneous liberation of large amount of energy. Nuclear fission occurs in sun.

1H2 + 1H2 2He4 + energy4. Give any two differences between nuclear fission and fusion.

5. What is a nuclear chain reaction?


S.No Nuclear fission Nuclear fusion1 It is the process of breaking heavier

nucleusIt is the process of combination of lighter nuclei

2 It emits radioactive rays. It does not emit radioactive rays.3 Occurs at ordinary temperature. Occurs at high temperature(>106 oK)

13



PART A WITH ANSWERS

A fission reaction where the neutrons from the previous step continue to propagate and repeat the

reaction is called nuclear chain reaction.

6. Define (a) super critical mass and (b) sub-critical mass of U235.

Super critical mass: If the mass of the fissionable material (U235) is more than the critical mass, it is

called super critical mass.

Sub-critical mass: If the mass of the fissionable material is less than the critical mass, it is called

sub-critical mass.

7. Give any one nuclear fission reaction, mention the factors that impede the nuclear chain reaction .

92U235 + 0n1 [92U236] 56Ba140 + 36Kr 93 +3 0n1

The factors that impede the nuclear chain reactions are:

i. Some of the neutrons may escape from the surface to the surroundings.

ii. Some of the neutrons may be absorbed by U238 present as impurity.

8. What are the types of nuclear fission reaction?

The nuclear fission reactions are of two types:

i. Uncontrolled fission reaction- Atom bomb

ii. Controlled fission reaction- Nuclear reactor

9. What is a nuclear reactor?

The arrangement or equipment used to carry out fission reaction under controlled conditions is

called nuclear reactor.

10. What is the function of control rods? Give examples.

Control rods are movable rods used to control the fission reaction. They are suspended between the

fuel rods. They control the reaction by absorbing excess electrons.Cd113 and B11 are used as control

rods.

11. What are moderators? Give some examples.

The substances used to slow down the neutrons are called moderators.

Examples: Ordinary water, Heavy water, Graphite, Beryllium.

12. What is Breeder reactor?

Breeder reactor is one which converts non-fissionable material (U238, Th232) into fissionable material

(U235, Pu239).

13. What are fissile nucleides and fertile nucleides?

1. Fissionable nucleides such as U235&Pu239 are known as fissile nucleides.

2. Non-fissionable nucleides such as U238&Th232 are known as fertile nucleides.




PART A WITH ANSWERS

14. What is meant by solar energy conversion? How is it done?

Solar energy conversion is the process of conversion of direct sunlight into more useful forms. The

conversion of solar energy occurs by the following two mechanisms.

1. Thermal conversion

2. Photo conversion

15. What are thermal conversion and photo conversion?

Thermal conversion involves absorption of thermal energy in the form of IR radiation. Solar energy

is an important source for low temperature heat (< 100oC) which is useful for heating buildings,

water and refrigeration.

Photo conversion involves conversion of light energy directly into electrical energy.

16. What is solar cell? (or) Give a note on solar cell and its features.

Solar cell is a photo galvanic cell which converts solar energy directly into electrical energy.

It consists of p-type semiconductor (such as Si doped with B) and n-type semiconductor (such as

Si doped with P) in close contact with each other.

17. Explain the applications of solar cells.

1. Solar cells are used in calculators, electronic watches, radios and TVs.

2. They are superior to other type of cells because non-polluting and eco-friendly.

3. Solar energy can be stored in Ni-Cd batteries and lead-acid batteries.

4. Solar cells can be used to drive vehicles.

5. Solar cells made of Silicon are used as a source of electricity in space craft and satellites.

18. What are fuel cells?

Fuel cell is a voltaic cell, which directly converts the chemical energy of the fuels directly into

electricity without combustion. In these cells the reactants, products and electrolytes pass through

the cell.

Fuel + Oxygen → Oxidation products +Electricity

19. What are the applications of the H2-O2 fuel cell?

1. H2-O2 fuel cells are used as auxiliary energy source in space vehicles, submarines or other

military vehicles.

2. In case of H2-O2 fuel cells, the product (water) has proved to be a valuable source of fresh water

to the astronauts.

20. What is wind energy? How is it obtained?




PART A WITH ANSWERS

Moving air is called wind. Energy obtained from the force of wind is called wind energy. The

energy possessed by wind is because of its high speed. The wind energy is harnessed by using wind

mills.

21. What are the drawbacks of Wind energy?

1. The noise generated by the wind mill makes wind farms unpopular with the public. The

appearance of wind mill is unaesthetic.

2. Wind farms located on the migratory routes of birds are hazardous to them.

22. What is a battery? How does it differ from a cell?

A battery is an arrangement of several electrochemical cells connected in series, that can be used as

a source of direct electric current. A cell contains only one anode and cathode whereas a battery

contains several anodes and cathodes.

23. What are the requirements of a battery?

The important requirements of a battery are:

It should be light and compact for easy transport.

It should have long life both when it is being used and when it is not used.

The voltage of the battery should not vary appreciably during its use.

24. What are secondary cells?

In secondary cells, electrochemical reactions can be reversed by passing current from an external source.

Therefore they can be recharged and used again and again. They are also called Storage cells Or

Accumulators. E.g., Lead acid storage cell.

25. What is a dry cell? Give one example.

Dry cell does not use any fluid. E.g., Leclanche cell (Zinc-carbon dry cell).It consists of a zinc cup

as the anode and a carbon rod as anode. The Zinc cup is filled with a mixture of MnO 2, NH4Cl

andZnCl2 and carbon powder.

26. What is an alkaline battery?

It is an improved form of dry cell, in which NH4Cl is replaced by KOH. In alkaline battery , the

powdered zinc is mixed with KOH and MnO2 to get a gel.

27. Write the overall equation for the reaction taking place in alkaline battery?

At Anode: Zn(s) + 2 OH- → Zn(OH)2(s) + 2e-

At Cathode: 2 MnO2(s) +H2O (l)+ 2 e- → Mn2O3 (s) + 2 OH-(aq)

Overall Cell Reaction Zn(s) + 2 MnO2(s) +H2O (l) → Zn(OH)2(s)+ Mn2O3 (s)

28. What are the advantages of alkaline battery (over dry battery)?




PART A WITH ANSWERS

1. An alkaline battery maintains better voltage as the current is drawn from it.

2. The life of alkaline battery is longer than dry battery , because there is no corrosion of

zinc.

3. Zinc does not dissolve readily in a basic medium.

4. Even in hot weather it performs better than other types of batteries.

29. Write the cell representation of lead storage cell.

The cell may be represented as:

Pb| PbSO4 || H2SO4 (aq) | PbO2 | Pb

30. Write the charging and discharging reaction of lead accumulator.

Charging

Pb(s) + PbO2(s) + 2H2SO4(aq) =========== 2 Pb SO4(s) + 2H2O + Energy

Discharging

31. What are the applications of lead acid storage cell ?

1. Lead acid storage cell is used to supply current mainly in automobiles such as cars,

buses, trucks, etc.,

2. It is also used in gas engine ignition, telephone exchanges, hospitals, power stations .

32. Write the cell representation of NICAD battery?

Cd | Cd (OH)2 || KOH(aq) | NiO2 | Ni

33. What are the advantages and disadvantages of NICAD battery?

Advantage:i. It is smaller and lighter.ii. Like a dry cell, it can be packed in a sealed container.iii. It has longer life than lead storage cell.

Disadvantage: It is more expensive than lead storage battery.34. How is NICAD battery constructed?

Nickel-cadmium (NICAD) cell consists of a cadmium anode and a small metal grid containing a

paste of NiO2 acting as a cathode. The electrolyte in this cell is KOH.

35. Lithium battery is the cell of the future. Why?

i. Its cell voltage is high, 3V.

ii. Since Li is a light-weight metal, only 7g(1mole)material is required to produce

1mole of electrons.

iii. Since Li has the most negative Eo value, it generates a higher voltage than the other

types of cells.




PART A WITH ANSWERS

iv. Since all the constituents of the battery are solids there is no risk of leakage from the

battery.

v. This battery can be made in a variety of sizes and shapes.

36. What are the merits of wind energy?

i. It is very cheap and economic.

ii. It is renewable.

iii. Does not cause pollution.

37. What are primary cells?

In primary cells, the electrode reactions occur only once and cannot be reversed by passing an

external electrical energy. The primary cells become dead after use. Therefore they are not

rechargeable. E.g., Leclanche’s cell

38. What is supercapacitor? Give examples? Supercapacitor is a high-capacity capacitor with capacitance values much higher than other

capacitors (but lower voltage limits) that bridge the gap between electrolytic capacitors and

rechargeable batteries.

39. Give any two differences between battery and supercapacitor.


S.No Supercapacitor Battery1 The potential energy in a capacitor is

stored in an electric fieldbattery stores its potential energy in a chemical form.

2 Does not involve chemical reactions Does involve chemical reactions3 High power density, and do not lose

their storagelow power density and lose their ability to retain energy throughout their lifetime due to material damage.

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