CBSE 12th Standard Chemistry Subject Value Based Questions 5 Mark Questions With Solution 2021
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CBSE 12th Standard Chemistry Subject Value Based Questions 5 Mark Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Chemistry
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Molecular nitrogen is very little reactive chemically, During lightning discharge, atmospheric nitrogen and oxygen combine at high temperature to form nitric oxide (NO) which is then oxidised to nitrogen dioxide (NO2), Ozone also combines with nitric oxide to form nitrogen dioxide. Both NO and NO2 constitute smog which is very poisonous. It can cause burning sensation in the eyes and adversely affects respiratory system.
(i) What is the colour of nitrogen dioxide?
(ii) What happens when nitrogen dioxide is dissolved in water?
(iii) Suggest ways to check pollution caused by photochemical smog?
(iv) If Rachna would have decided to make people aware about it through street plays and posters, then what are the values shown by her?(a) -
Gasoline is being used worldwide for running automobile, aeroplane etc. Due to the presence of nitrogen and sulphuric compounds in gasoline, the exhaust gases contain oxides of nitrogen and sulphur which are major pollutants in the environment in contrast, ethanol is a much cleaner fuel because it produces only CO2 and Hp. Now answer the following questions:
(a) Besides being a cleaner fuel, what are the other advantages of using ethanol as a fuel in automobile?
(b) What are the disadvantages of using ethanol as a fuel? What are the value associated with its use?(a) -
Miss Usha was asked to synthesize alcohol by acidic hydration of l-butene. She was unaware of the fact that the vessel she used had some coating of a metal, and in addition to alcohol, compound X was I isolated X forms bisulphate compound as well as 2, 4-dinitrophenylhydrazone. Separation of alcohol could be made by physical as well as by chemical methods.
(i) How are alcohol and Xformed?
(ii) Can alcohol and Xgive iodoform test?
(iii) Give different methods of separation?
(iv) What value did Miss. Usha lack?(a) -
Mohan heard a lot of noise and weeping in nearby jhuggis he look courage and went to enquire what had happened. He found that some people has taken spurious alcohol containing methanol and were crying with pain and were complaining of loss of eyesight. He immediately hired an auto rickshaw and packed it with 4 persons who has consumed spurious alcohol.
(i) How does methanol in drinking alcohol cause problem?
(ii) What treatment might the doctors have undertaken to save the patients?
(iii) What message would you give to the person who consumed spurious alcohol?(a) -
A teacher ordered ethanol for laboratory. She preferred denatured alcohol over absolute alcohol.
(i) Give reason for the decision taken by the teacher.
(ii) What value was kept in mind while taking the decision?(a)
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CBSE 12th Standard Chemistry Subject Value Based Questions 5 Mark Questions With Solution 2021 Answer Keys
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(i) Nitrogen dioxide is reddish brown in colour. 1
(ii) A mixture of HNO2 and HNO3 is formed.
\(2NO_{ 2 }+H_{ 2 }O\longrightarrow HN0_{ 2 }+HNO_{ 3 }\)
(iii) Oxides of nitrogen are also released from the engines of vehicles in which petrol and diesel burn. To check this, engines of automobiles are fitted with catalytic converters which check the release of oxides of nitrogen and vapours of hydrocarbons in the atmosphere.
(iv) Control of photochemical smog can provide relief from diseases linked with respiratory system such as cough, cold, bronchitis, asthma etc. If Rachna makes people aware through her different efforts then she is environment friendly, socialy active, etc. -
(a) The main advantages are:
(i) It is made from renewable energy sources i.e., sugarcane and com which are grown in the field.
(ii) It has higher octane rating.
(iii) Due to the presence of oxygen in ethanol, poisonous gases like CO and unburnt hydrocarbon are emitted to a lesser extent.
(iv) Less dependence on imported oils thereby promoting the economy of our country.
(b) The main disadvantages are :
(i) It has one-third the energy content than the gasoline. Thus drivers will need more ethanol than gasoline to drive the same distance.
(ii) Ethanol can absorb water and dust more easily and hence corrodes engine made up of Al.
(iii) It produces cancer causing emissions such as acetaldehyde and formaldehyde forty times more than gasoline. Social awareness, Social awareness, eco-friendiness are the values associated with the use of ethanol as fuel. -
(i) \({ CH }_{ 3 }-{ CH }_{ 2 }-CH={ CH }_{ 2 }+{ H }_{ 2 }O\overset { { H }^{ + } }{ \longrightarrow } { CH }_{ 3 }{ CH }_{ 2 }(OH){ CH }_{ 3 }\)
Since X forms bisulphate and 2, 4-dinitrophenylhydrazone, it means Xhas carbonyl group formed due to oxidation of alcohol. This oxidation is due to coating of metal (Cu).
\({ CH }_{ 3 }{ CH }_{ 2 }(OH){ CH }_{ 3 }\longrightarrow { CH }_{ 3 }{ CH }_{ 2 }CO{ CH }_{ 3 }(ketone/X)+{ H }_{ 2 }I\)
(ii) Alcohol and X both give iodoform test.
(iii) Alcohol and X can be separated by
(a) Distillation
(b) BisulpIilte formation only (X) forms Bisulphite complex (s) which can be decomposed.
(iv) Usha lacks critical awareness of chemistry. -
(i) Methyl alcohol is easily oxidized to formaldehyde and then to formic acid which may cause blindness and death.
(ii) Doctors give an intra venous infusion of diluted ethanol the enzyme responsible for oxidation of HCHO to acid is swamped allowing time for kidneys to excrete methanol.
(iii) People should be educated not to drink cheap alcohol from unauthorized sources. It is not worth saving money when the life get endangered. If at all one has to drink, the stuff must be purchased from an authorized source. -
(i) Teacher preferred denatured alcohol over absolute alcohol as it would be unfit for drinking. As commercial alcohol is mixed with copper sulphate to give it a colour and pyridine to give a foul smell, which makes absolute alcohol unfit for drinking and called as denatured alcohol.
(ii) As the teacher was ordering ethanol for school laboratory, maintaining discipline, repsonsible behaviour and social obligation were values kept in her mind, while taking decision.
