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Chapter: Chemistry : Energy Sources

Important Questions and Answers: Energy Sources

Chemistry - Energy Sources - Important Questions and Answers: Energy Sources



1. What is nuclear energy?


The energy released by the nuclear fission reaction is called nuclear energy.


2. What is nuclear fission reaction?

The process of splitting of heavy nucleus into two or smaller nuclei with


Simultaneous liberation of large amount of energy in the form of heat is known as nuclear fission reaction.


3. What is nuclear fusion reaction? Give one example.

The process of combination of two or more lighter nuclei into heavier nuclei, with simultaneous liberation of large amount of energy is known as nuclear fusion reaction.


4. Differentiate nuclear fission and fusion reaction.

Nuclear fission

It is the process of breaking the heavier


It emits radioactive rays

Occurs at ordinary temperature

Chain reaction takes place

Emits neutrons

It can be controlled


Nuclear fusion

It is the process of

combination of lighter nuclei.

Does not emit radioactive rays.

At high temperature(>106K)

No chain reaction.

Emits positrons

Cannot be controlled


5. Define nuclear chain reaction.


It is a nuclear reaction, in which neutrons from a previous step propagate and repeat the reaction. It takes place only nuclear fission reaction.



6.What are fissile and fertile nucleides?


7. What are solar cells? Give one example./What is a photo galvanic cells?

It is a device, Converting solar energy directly into electrical energy.


It provides power supply for space satellites. Ex: solar water heater , photovoltaic cell


8. What is solar energy conversion?


It is the process of conversion of direct sunlight into more useful forms.


It undergoes mainly two types of mechanisms. 1. Thermal conversion. 2. Photo conversion 

9. What are the merits of wind energy?


a) Nonpolluting and sustainable energy source.b).The scope of wind energy is enormous. c). It is a renewable and sustainable energy source.


d).  It is available in many offshore, onshore and remote areas.


10. What are batteries?


It is a device, converted chemical energy into electrical energy. It is an arrangement of electrochemical cells connected in series,and it can be used as a source of direct electric current.


11. Define breeder reactor.

Breeder reactor is one which converts non-fissionable material into fissionable material.


12. What are non-conventional energy sources? Give two examples.


Non-conventional energy sources are those energy sources which are exposed to use from modern technological advancements; rather than the normal use of conventional fuels as


energy sources like gas or oil.


Ex: 1. Wind energy 2. Solar energy 3.Tidal energy 4. Hydropower energy


13. What is a fuel cell?

It is a device in which the chemical energy of the fuel hydrogen is directly converted into electrical energy without combustion.


Fuel + Oxygen → Oxidation products + Electricity.


14. What are the advantages of fuel cell? Or  What are the advantages of H2-O2 fuel cell?


It is used as an auxiliary energy source in space vehicles, submarines.


Used in military vehicles. It is a pollution free one.The product is water, so it is a valuable source of fresh water by the astronauts.


15. What are the applications of lithium batteries?


Used in cell phones, Digital cameras, Watches, Remote cars, Calculators, Toys, Backup batteries in computers, etc.


16. List any two advantages of lithium batteries.


Its cell voltage is high, 3V. Li is a light-weight metal, only 7g (1 mole) material is required to produce 1 mole of electrons. It contains solid material so there is no leakage from battery. This battery can be made in a variety of sizes and shapes.



15.Define alkaline battery.


It is called as a dry cell.>It has the electrolyte of KOH


A zinc cylinder is filled with an electrolyte of Zn,KOH and MnO2 A carbon rod acts as a cathode and zinc body acts as a anode.


16.What are the general components in nuclear reactor?


The components are fuel rods, control rods, moderators, reflectors, coolants and pressure vessel, Turbine







1 Distinguish between Nuclear fission and Nuclear fusion reaction.

Nuclear fission

1.       Breaking a heavy nucleus into smaller

2.       Emits radioactive rays

3.       Reaction takes place at ordinary temperature

4.       It gives chain reaction.

5.       Emits neutron

6.       It can be controlled

7.       The mass number and atomic number of new elements are lower than the parent nucleus.

8.       Ex: Fission reaction of 92U235, power generation in Nuclear Power Plant, Kalpakkam&koodankulam, Tamilnadu.


Nuclear fusion

1. Combination of two smaller nuclei.

2. Does not emit radioactive rays

3. At high temperature. > 106K.

4. No chain reaction

5. Emits positron

6. It cannot be controlled.

7. Higher than that of starting elements.

8. Ex: Fission reaction takes place in sun.


2. Define Nuclear fission reaction. Explain with one example in detail.



03. Explain Nuclear Reactor-Power Generator with neat diagram./ Light Water Reactor


Nuclear Reactor: A device used for power generation, in which a nuclear chain reaction is initiated, maintained and controlled to produce the heat energy is known as nuclear reactor.




1)                Fuel Rods:  It produces heat energy and neutrons.

                             Ex: Natural Uranium (99.28% U238 and 0.714 % U235) and Pu239

2) Control Rods:  To keep power production at a steady state.

                             Ex: Boron and Cadmium rods.

3)      Moderators:         Function to reduce the kinetic energy of fast fission neutrons to slow

                             neutron and this is done in a small fraction of a second.

                             Ex: Graphite, Be, Ordinary water and Heavy water.

4)      Coolants:    To remove the intense heat produced in the reactor and to bring it out for

                             utilization. Ex: Ordinary water, Heavy water, liquid metals and gases.

5)      Reflector:    It placed around the core to reflect back some of the neutrons that leak out

                             from the surface of the core.

6)      Pressure vessel: It enclosed the core and reflector. It also provides the entrance and exit passages for coolant. (Pressure 200 kg/cm2)

7)      Shielding:    To attentiate the Gama rays and other radiations coming out from the reactor. 2 Types. (i). Thermal shield  (ii). Biological shield.

8)      Turbine:      The steam at high pressure, generated in the heat exchanger is used to operate a steam turbine, which derives a generator to produce electricity.


04. Explain Breeder reactor with reactions.


 05. Define solar cell. Explain solar energy conversion in detail.


Solar cell = Photogalvanic cell : It is a device used for converting solar energy into electricity. It is made by interconnecting a large number of photovoltaic cells.

Solar Energy Conversion: It is the process of conversion of direct sunlight into more useful forms. Conversion may be in two forms. 1. Thermal Conversion. 2. Photo Conversion.


01. Thermal Conversion:


It involves absorption of thermal energy in the form of IR radiation. Temperature below 100oC, is useful for heating purpose of water and refrigeration.

Methods: (i).Solar heat collectors.   (ii).Solar water heater.


(i). Solar heat collectors: It consists of natural materials like stones, bricks which can absorb heat during the day time and release it slowly at night.


Uses: It is used for houses in cold condition.


(ii). Solar Water Heater:

It consists of an insulated box inside of which is painted with black paint. There is a provision for sun light absorption using a glass lid and store solar heat. Inside the black painted, copper coil and cold water is flow in and gets heated and storage in a tank.


02. Photo Conversion: 

It involves conversion of light energy directly into electrical energy.

Methods: Solar Cell.

Solar Cell: Ex: Solar light, solar pump, solar battery.

It is a device, converting solar energy directly into electrical energy.

Principle: When solar rays fall on a two layer of

semi-conductor devices, a potential difference between the two layers is produced. This potential difference causes flow of electrons and produces electricity.


Working: When the solar ray falls on the top layer and the e-s promoted to the conduction into n-type semiconductor. The potential difference occurs; it should lead current increasing (i.e) flow e-s. They are connected with an external circuit, and current is generated.


Applications of Solar Energy :(i). Used in calculators,Watches, etc. (ii). Used to drive Vehicles.


(iii). Used in boilers to produce hot water for domestic and Industrial uses.


(iv). Used for lighting purposes. (v). Used as a source power in space crafts and satellites. (vi). Used for producing hydrogen by hydrolysis of H2O.


Demerits of Solar Energy: (i). Huge capital cost.

(ii). Not available during night and cloudy days. (iii). Storage of energy is not possible

06. Write a short note on Wind Energy.


Moving energy is called Wind.Energy recovered from the force of the wind is called wind energy. The wind energy is harnessed by making use of wind mills.


01.Wind Mills:


The strikes of blowing wind on blades of the wind mill make it rotating continuously.


The rotational motion of the blade drives a number of machines like water pump, flour mills and electric generators.


Wind mills are capable of generating about 100 kw electricity.




02. Wind Farms.


It is known as the large number of joining wind mills called wind farm. It produces a large amount of electricity.The minimum speed required for working of a wind generator is 15 km/hr


03. Other methods: (i). Sky Sail        (ii). Ladder


mill. Advantages/ Merits of Wind energy:


i. It does not cause any Air pollution. ii. It is very cheap and economic.


iii.      It is renewable.


Disadvantages of Wind energy:


i.        It produces noise.


ii.       It produces unwanted sound.


          Affects bird‟s life.


          Affected to the radio signals.




7. Define Battery. Explain with its types.




It is a device, converted chemical energy into electrical energy. It contains several anodes and cathodes.


It is an arrangement of several electrochemical cells connected in series and it can be used as a source of direct electric current. (D.C).






i.  It is known as Non-Reversible battery.


ii. Electrode and electrode reactions cannot be reversed by passing an external current. iii. Reactions take place only once and after use they become dead.


iv. They are not chargeable.


            Ex: Dry Cell, Mercury Cell, Leclanche‟s cell.





          It is known as Reversible battery.


ii. Electrode and electrode reactions are reversiblewhen an external current is passing iii. It can be recharged again and again.


iv. Also called as Storage cells or Accumulators. v. Ex: Lead-Acid Battery, Ni-Cd.




In these cells, the reactants, products and electrolytes and continuously passing through the cell. Here chemical energy is converted to electrical energy.


Ex: H2-O2 fuel cell.


08. Explain Alkaline Battery with neat diagram and cell reactions.

Anode : Zinc body

Cathode : Carbon rod / Graphite rod

Electrolyte : Powdered KOH, MnO2  in the form of paste.

Alkaline battery consists of electrolyte KOH and a Zinc cylinder filled with powdered Zn, KOH and MnO2 in the form of paste using starch and water. A carbon rod [Graphite] acts as a cathode and it is immersed in the electrolyte in the centre of the cell. The outside cylindrical


zinc body acts as an anode.





 Zinc doesn‟t dissolve in a basic medium.


ii. Its life is longer than dry battery because there is no corrosion on Zn. iii. It maintains its voltage, when the current is drawn from it.




It is used in calculators and watches.


09. Explain Lead acid storage battery.

Cell Representation: Pb/Pb(SO)4//H2(SO)4(aq)/PbO2/Pb

Anode : Lead - Pb

Cathode : Lead Oxide PbO2

Electrolyte : Sulphuric acid -  H2(SO)4


This is also a rechargeable battery.It consists of number of voltaic cells. In each cell, anode is Pb plate and cathode is PbO2


A known number of lead plates are connected with parallel and a number of PbO2 plates and also connected in parallel. Various plates are separated by insulators like glass fibre. The total anodes and cathodes are immersed in dil.H2(SO)4 Solution.


Cell reactions: Discharging



(i). It is made easily.                         (ii). It produces very high current.


(iii). Effective one at low temperature.      (iv). Self- discharging rate is low.




(i). Used in automobiles like Car, Bus, Van, Lorry, Bike etc.

(ii). Used in Hospitals, Power stations, Telephone exchanges etc.


10. Explain Nickel – Cadmium battery with cell reactions.

Cell Representation: Cd/Cd(OH)2//KOH(aq)/NiO2/Ni

Anode : Cadmium (Cd)

Cathode : A metal grid containing a paste of NiO2

Electrolyte : KOH

This is also a rechargeable battery.


It consists of Cd anode and a metal grid containing a paste of NiO2 acts as a cathode. The  electrolyte is KOH.


Discharging: When Ni-Cd battery operates, Cd gets oxidation and forms Cd2+ and insoluble Cd(OH)2 is formed. Its emf value is 1.4 V.


Cell  Reaction:




Recharging: When an current is passed opposite direction, the cell reaction is reversed. As a result, Cd gets deposited on anode and NiO2 on cathode.



(i). It is smaller and lighter.


(ii). It has longer life than lead storage cell.




(i). It is used in calculators, Electronic devices. 

(ii). Used in transistors, cordless appliances.




11. Explain Lithium batteries in detail.


It is known as solid state battery because the electrolyte is used here at solid state.

Anode : Lithium (Li)

Cathode : TiS2

Electrolyte : Polymer



When the anode is connected to cathode, Li+ ions move from anode to cathode. Anode is Li and cathode is TiS2 and the electrolyte is solid polymer. The cathode is a material capable of receiving the Lithium ions and electrons.




LiTiS2 -- -- >    Li+ + TiS2-



It is recharged by applying an external current. Emf of Li cells = 3.0V.


Advantages: (i). Itsemf is high 3.0V.


(ii). It is a light weight material only 7g required for produce 1 mole of e-s.




12. Explain Hydrogen- Oxygen Fuel cell / [H2 – O2] Fuel cell.



Fuel Cell: It is a device in which the chemical energy of the fuel hydrogen is directly converted into electricity without combustion.



Anode : Hydrogen

Cathode : Oxygen ( oxidizer)

Electrolyte : 25% KOH or NaOH

Two porous electrodes – Made of compressed carbon containing a catalyst like pt / pd.

It consists of two porous electrodes anode and cathode. In between two electrodes an electrolytic solution 25% KOH or NaOH filled.

When H2 is bubbled through the anode compartment, where it is oxidized. The O2 is bubbled at the cathode compartment where it is reduced.

The emf of the cell = 0.8 to 1.0 V. Merits:


 High efficiency.


ii. No unwanted noise and less maintenance. iii. No pollution


                    No need to change electrode often. Uses:

                Used in military vehicles and space vehicles.

                       H2 – O2 fuel cell, the product is water, so no need of fuel because fuel is water

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