1. Explain briefly on (characteristics of) rocket propellants. Or Write a note on Rocket propellants.
1. Rocket motors are used both in space vehicles and in offensive weapons such as missiles. The propulsion system in most space vehicles consists of rocket engines powered by chemical propellants. These also called rocket propellants.
2. Propellants are combustible compounds which on ignition undergo rapid combustion to release large quantities of hot gases. A propellant is a combination of an oxidiser and a fuel.
Working of a propellant:
When a propellant is ignited, it burns to produce a large quantity of hot gases. These gases then come out through the nozzle of the rocket motor. The passage of gases through the nozzle of the rocket motor, provides the necessary thrust for the rocket to move forward according to the Newton’s Third law of Motion (to every action, there is an equal and opposite reaction).
Examples:
Hydrazine, Liquid hydrogen, Polyurethane, etc.
2. Explain briefly on colour and structure of dyes.
The relationship between the colour of a substance and its structure was explained by a German scientist Otto Witt through the chromophore and auxochrome theory.
According to this theory,
1. An organic compound appears coloured due to the presence of certain unsaturated groups (the groups with multiple bonds) in it. Such groups with multiple bonds are called chromophores.
Examples:
2. The compounds containing the chromophore group is called chromogen. The colour intensity increases with the number of chromophores or the degree of conjugation.
For example, ethene (CH2 = CH2) is colourless, but the compound CH3 – (CH = CH)6 – CH3 is yellow in colour.
3. The presence of certain groups which are not chromophores themselves, but deepen the colour of the chromogen. Such supporting groups are called auxochromes. Auxochromes may be acidic (phenolic) or basic.
Examples:
Some important auxochromes are –OH, –NH2, –NHR, NR2.
The presence of an auxochrome in the chromogen molecule is essential to make it a dye. However, if an auxochrome is present in the meta position to the chromophore, it does not affect the colour.
For example, in the compound p-hydroxyazobenzene (a bright red dye),
3. Give the characteristics of a dye.
1. Should have a suitable colour.
2. Should be able to fix itself or be capable of being fixed to the fabric.
3. Should be fast to light.
4. Should be resistant to the action of water, dilute acids and alkalies (all detergents and washing soaps are alkaline in nature).
4. How are Buna-S and Nylon-66 prepared?
Buna-S is prepared by the polymerization of butadiene and styrene in presence of sodium metal.
Nylon-66 is prepared by condensing adipic acid with hexamethylenediamine with the elimination of water molecule.
5. What are chromophores and auxochromes? Give two examples for each.
Chromophores:
An organic compound appears coloured due to the presence of certain unsaturated groups (the groups with multiple bonds) in it. Such groups with multiple bonds are called chromophores.
Examples:
Auxochromes:
The presence of certain groups which are not chromophores themselves, but deepen the colour of the chromogen. Such supporting groups are called auxochromes. Auxochromes may be acidic (phenolic) or basic.
Examples:
Some important auxochromes are –OH, –NH2, –NHR, NR2.
6. Write a note on anaesthetics.
The drugs which produce loss of sensation are called anaesthetics.
They are classified into two types.
1. General anaesthetics are the agent, which bring about loss of all modalities of sensation, particularly pain along with ‘reversible’ loss of consciousness.
2. Local anaesthetics prevent the pain sensation in localised areas without affecting the degree of consciousness.
Examples:
Nitrous oxide, N2O
Chloroform, CHCl3
Ether, C2H5–O–C2H5
7. Write briefly on Buna rubbers.
Buna rubbers are obtained as a result of polymerisation / copolymerization of butadiene with acrylonitrile or styrene. There are two types of Buna rubbers.
1. Buna-S is obtained by the polymerization of butadiene and styrene in presence of sodium metal.
Properties: Neoprene and Buna-S are extremely resistant towards wear and tear
Uses: for the manufacture of tyres, rubber tubes and other mechanical rubber goods.
2. Buna-N is obtained as a result of copolymerisation of two parts of butadiene with one part of acrylonitrile in the presence of sodium metal.
Properties: Buna-N rubber is hard and extremely resistant to the swelling action of oils (petrol), solvents, heat etc.
Uses: for the manufacture of storage tanks for the solvents.
THREE MARKS
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