CBSE Class 12 Chemistry Alcohols Phenols And Ethers VBQs

SHORT ANSWER TYPE QUESTIONS

Question. Write one chemical reaction to illustrate the following :

(i) Reimer-Teimann reaction

(ii) Williamson’s synthesis

Answer:

Question. Account for the following :

(i) Phenol has a smaller dipole moment than methanol.

(ii) Phenol goes electrophilic substitution reactions.

Answer: 

(i) Due to – ve charge on oxygen in delocalized by resonance.

(ii) Due to greater electron density than benzene.

Question. Complete the following equations and name the products :

Answer:

 

Question. Write :

(i) Friedel-Crafts reaction

(ii) Coupling reaction

Answer:

Question. Give one reaction of alcohol involving cleavage of :

(i) C – O bond

(ii) O – H bond

Answer: 

(i) CH₃CH₂OH + PCl₅ → CH₃CH₂Cl + POCl₃ + HCl

(ii) CH₃CH₂OH + Na → CH₃CH₂ONa + H₂

Question. Etherial solution of an organic compound ‘X’ when heated with Mg gave ‘Y’. ‘Y’ on treatment with CH₃CHO followed by acid hydrolysis gave 2-propanol. Identify the compound ‘X’. What is ‘Y’ known as ?

Answer:

Question. While separating a mixture of o- and p-nitrophenols by steam distillation name the isomer which is steam volatile. Give reason.

Answer:

H-bonding and association of molecules.

Question. Account for the following :

(i) Phenol has a smaller dipole moment than CH₃OH.

(ii) Phenol do not give protonation reactions readily.

Answer: 

(i) Because phenol has electron attracting benzene ring.

(ii) Resonance and +ve charge oxygen does not have tendency to accept a proton.

Question. Write the reactions and conditions involved in the conversion of :

(i) Propene to propan-2-ol.

(ii) Phenol to salicylic acid.

Answer:

Question. Write mechanism of reaction of HI with methoxymethane.

Answer:

Question. Arrange in order of boiling points :

(i) C₂H₅ – O – C₂H₅, C₄H₉COOH, C₄H₉OH

(ii) C₃H₇CHO, CH₃COC₂H₅, C₂H₅COOCH₃, (CH₃CO)₂O

Answer:

(i) C₄H₉COOH > C₄H₉OH > C₂H₅ – O – C₂H₅

(ii) (CH₃CO)₂O > C₂H₅COOCH₃ > CH₃COC₂H₅ > C₃H₇CHO

Question. Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why ?

Answer:

It is because of double bond character, (C – Br) bond in

due to resonance it is less reactive towards SN, RXN.

Question. Ethers are relatively inert. Justify.

Answer: 

Due to absence of any active site in their molecules, divalent oxygen is linked to carbon atoms on both sides

Question. How will you distinguish between CH₃OH and C₂H₅OH ?

Answer:

CH₃OH does not give this test.

SHORT ANSWER-II TYPE QUESTIONS

Question. Name the reagents which are used in the following conversions :

(i) 1º alcohol to an aldehyde

(ii) Butan-2-one to butan-2-ol

(iii) Phenol to 2, 4, 6 tribromophenol

Answer: 

(i) PCC, a complex of chromium trioxide with pyridine and HCl.

(ii) NaBH₄, sodium borohydride.

(iii) Br₂ (water)

Question. Write structures of the major products of the following :

(i) Mononitration of 3-methylphenol

(ii) Dinitration of 3-methylphenol

(iii) Mononitration of phenyl ethanoate

Answer: 

OH and – CH₃ are o- and p-directing groups. The products are :

Question. Complete the following reactions :

Answer:

(i) CH₃CH₂CH₂CH₂OH

(ii) CH₃CH = CHCH₂ – OH

(iii) CH₃CH₂CH₂OH

(v) CH₂OH – CH₂OH

(vi) CH₃CH₂OH

Question. Give equations of the following reactions :

(i) Oxidation of propan-1-ol with alkaline KMnO4 solution.

(ii) Bromine in CS₂ with phenol.

(iii) Treating phenol with chloroform in presence of aqueous NaOH.

Answer:

Question. Describe the following reactions with examples :

(i) Reimer-Teimann reaction

(ii) Kolbe’s reaction

(iii) Friedel Crafts acylation of anisole

Answer:

Question. Dehydration of alcohols to form an alkene is always carried out with conc. H₂SO₄ and not with conc. HCl or HNO₃. Explain.
Answer:

In acidic medium alcohols protonated then loses H₂O to form a carbo cation.

If HCl Cl− strong nucleophile cause nucleophilic substitution, HNO₃ causes oxidation.

Question. How will you convert :

(i) Phenol to cyclohexanol

(ii) Benzyl chloride to benzyl alcohol

(iii) Anisole to phenol

Answer:

LONG ANSWER TYPE QUESTIONS 

Question. An alcohol A (C₄H₁₀O) on oxidation with acidified K₂Cr₂O₇ gives carboxylic acid ‘B’ (C₄H₈O₂). Compound ‘A’ when dehydrated with conc. H₂SO₄ at 443 K gives compound ‘C’ with aqueous H₂SO₄. ‘C’ gives compound ‘D’ (C₄H₁₀O) which is an isomer of ‘A’. Compound ‘D’ is resistant to oxidation but compound ‘A’ can be easily oxidized. Identify A, B, C and D and write their structure.

Answer:

A : (CH₃)₂CHCH₂OH B : CH₃CH(CH₃)COOH
C : (CH₃)₂C = CH₂ D : (CH₃)₃ – C – OH

Question. An ether ‘A’ (C₅H₁₂O) when heated with excess of hot concentrated HI produced two alkyl halides which on hydrolysis from compounds B and C. Oxidation of B gives an acid D whereas oxidation of C gave a ketone E.Deduce the structures of A, B, C, D and E.

Answer:

B : CH₃CH₂OH
C : CH₃CHOHCH₃ D : CH₃COOH
E : CH₃COCH₃

Question. Which of the following compounds gives fastest reaction with HBr and why?

Answer:

(i) (CH₃)₃C – OH
Due to formation of EDG and formation of cation.

Question. Phenol, C₆H₅OH when it first reacts with concentrated sulphuric acid,forms Y. The compound, Y is reacted with concentrated nitric acid to form Z. Identify Y and Z and explain why phenol is not converted commercially to Z by reacting it with conc. HNO₃.

Answer:

Phenol is not reacted directly with conc. HNO₃ because the yield of picric acid is very poor.

Question. Fill in the blanks :

Answer:

Question. Miss. Kamala was asked to synthesise alcohol by acidic hydration of 1-butane. She was unaware of the fact that the vessel she used had some coating of metal, and in addition to alcohol (bp.373 k), compound X (b.p.353K) was also isolated. X forms bisulphite compound as well as 2,4-dinitrophenyl hydrazone. Separation of alcohol could be made by physical as well as chemical methods.

(i) How is alcohol acid X formed?

(ii) Can alcohol acid X give iodoform test?

(iii) Give the different methods of separation. 

Answer:

(ii) Alcohol and X both give iodoform test.

(iii) Alcohol and can be separated by

(i) distillation

(ii) bisulphite formation only (X) forms bisulphite complex (solid) which can be decomposed.

Question. Ethanol, commonly called as alcohol is an excellent solvent and is used in medicines and synthesis of many chemical compounds. However in spite of its benefits to man its impact on social behavior has always been questioned. Media have often shown abnormal behavior of people while drunk. It is considered as a curse in the lives of those who are addicted to alcohol called alcoholic people because it not only affects their own lives but they are also a threat to the lives of others. Anger and rude behavior are some of its ill effects.

A) Comment on the statements ‘should production of alcohol be banned’. Give three valid reasons to justify

B) As a student of chemistry what initiative would you take in the common concern of ‘save life, do not drink ‘. give suggestion

Answer:

(A) though ethanol is one of the most important industrial chemicals, it has many harmful effects of the use of ethanol are

1) It causes death of many people

2) Many adolescents get affected out of it and become addict to alcohol.

3) It is being misused even where it is of important use, such as in painting shops, industries etc. Keeping in view its ill effects, its production should be banned

Ethanol is the only alcohol used for drinking purpose in spite of its many harmful effects. But in addiction to drinking purposes which causes many harmful effects, it has many important uses:

1) It is used as solvent for resins, fats, oils, fatty acids and hydrocarbon.

2) It is used in so many ways for medicines, lacquers, varnishes, perfumes etc.

3) It is used as disinfectant.

So it should not be banned but its production and supply should be regulated.

(B) – As a student of chemistry and keeping in view the ill effects and importance of ethanol, the following initiatives should be taken to “save life, do not drink “

1) Slogan writing

2) Skits or dramas showing ill effects of alcohol.

Question. The labourers of a colony used to drink cheaper alcohol from unauthorized sources. This alcohol contained some methanol. One day a few labourers complained of drowsiness and pain, and loss of eyesight after consuming the liquor. Their family members took them to the hospital and the doctors tried to treat them. One of the labourers died and the other complained loss of their eyesight. As a student of science, how would you analyse this serious situation?

1) How does drinking of cheap alcohol cause problem?

2) What message would you give to the persons who consume spurious alcohol?

Answer:

1) Due to the presence of highly toxic methanol

2) People should be educated not to drink cheap alcohol from unauthorized sources

Question. In a slum area large number of people fell ill after drinking liquor sold by a local vendor. Many people started vomiting, some complained of not being able to see properly and some others were unconscious. Gautam’s father also suffered from severe stomach ache after consuming liquor. Gautam calmed down his mother and helped her to call ambulance for his father and also for other people. They also informed the police about the incident.

1) Mention the values shown by Gautam
2) WRITE THE PROBABL CAUSE OF POISONING BY LIQUOR
3) Write the reaction showing the conversion of molasses to ethyl alcohol using yeast

Please refer to the link below for CBSE Class 12 Chemistry - Alchohols, Phenols and Ethers VBQs.

VALUE BASED QUESTIONS

CHEMISTRY

Alcohols, Phenol and Ethers

A teacher ordered ethanol for laboratory. She preferred denatured alcohol over absolute alcohol.

Contextual Question:-

a) Give reason for the decision taken by the teacher. 

Value Based Questions:-

b) What value was kept in mind while taking the decision? 

Value Points:-

* Maintaining discipline

* Concern for environment

* Responsible behaviour

* Social obligation.

Coordination Compounds

A student living on a hill station has surveyed the area and found most cases in hospital are of stones in gall bladder or kidney. He analyzed the water and found presence of Ca2+ ions. He conducted titration of water sample with EDTA (quantitative analysis) to prove his survey.

Contextual Question:-

a) What is the full form of EDTA? 

b) Why is EDTA preferred over any other ligand?

Value Based Questions:-

c) What values do you think were in mind of the student while conducting quantitative analysis? 

Values Points:-

* Social concern

* Awareness

* Responsible behavior

* Applied theoretical Knowledge to practice

d and f Block Elements

Mukta washes the vegetables with a very dilute solution of KMnO4.

Contexual Question:- a) What property of KMnO4 is used in this application. 

Values Based Questions:- b) In this process what values are shown by Mukta? 

Value Points:- 

* Responsible attitude

* Apply theoretical knowledge to daily life situation.

* Hygiene

* Awareness

* Concern for the health

 * Scientific aptitude

Chemistry In Everyday Life

During a trip to a remote village, students observed the villagers with swollen neck. They discussed it with the sarpanch and suggested a radical change in diet of villagers.

Contextual Question:-

a) What was the reason for the swollen neck and what changes in the diet was suggested.

Value Based question:-

b) What Values were exhibited by the students? 

Values Points:-

• Keen observational skill

• Concern for the community

• Awareness

• Alertness

• Using knowledge for practical use.

Solutions

The students went on a trip to the interiors of Kashmir. While coming back they were stuck on the road due to heavy snowfall. The students observed the villagers cleaning the road by scrapers. They suggested them to put the common salt on the snow to clear the road.

Contextual Question:-

a) What happens when common salt is sprinkled on snow? 

b) Show this phenomenon by graphical representation. 

Value Based Question:- 

a) What values got expressed in students’ suggestion? 

Value points:-

• Simplifying technology and applying it to daily life situation

• Awareness

• Helpfulness

• Scientific aptitude

Chemistry In Everyday Life

Rita wants to bake a cake for her friend’s birthday, who is diabetic. She prefers using artificial sweetening agent in place of sugar.

Contextual Question:-

a) Give one example of an artificial sweetener. 

Value based question:-

b) What value has been expressed in the above gesture? 

Value Points:-

• Care and concern

• Social responsibility

• Friendship

• Compassionate

Polymers

Natural rubber which is soft and brittle and shows high water absorption capacity becomes hard, less brittle and more flexible when it is heated with 5% sulphur.

Contextual question:-

a) Name the process by which properties of natural rubber are improved? What is the main purpose of the process? 

Value Based:-

b) Compare the human behaviour with the changing properties of natural rubber on heating with sulphur? 

Value Points:-

• Experimentation can bring innovations and changes in behaviour

• Imbibing positive traits

• Improvement in personality for the betterment of the society

Polymers

A large number of polymer applications in different fields depend upon their unique mechanical properties like tensile strength, elasticity, and toughness etc. These properties are governed by intermolecular forces present in the polymer

Contextual Question:-

a) Classify the polymers on the basis of intermolecular forces present in them.

Value Based Question:-

b) Outline any two values that we infer from the above paragraph. 

Value Points:-

• Strength

• Flexibility in behaviour

• Co-ordination while working in groups

Chemistry In Everyday Life

Certain analgesics are recommended by doctors to relieve severe pain and sleep disorder.

Contextual Question:-

a) Give the classification of analgesics with the help of suitable examples.

Value based question:-

b) As a chemist would you sell analgesics without prescription from the doctor? Why? 

Value Points:-

• Awareness about composition of drug

• Social responsibility (Narcotic analgesic are addictive.)

• Sensitive towards Health of fellow citizens.

Chemistry In Everyday Life

Birth control Pills contain a mixture of synthetic estrogen and progesterone derivatives.

Contextual Question:-

a) Give two examples of Antifertility drugs. Explain how they work in our body.

Value Based Question:-

b) How is the use of these drugs beneficial to the developing country like India?

Value Points:-

• Sensitive towards social problems (employment, food resources, environment issues)

• Gender sensitivity(health of females)

• Sustainable development

d and f Block Elements

An organization was secretly manufacturing an alloy which is used in the production of bullets and shells. A worker reported it to the police.

Contextual question:-

a) Name the alloy and write its composition. 

Value based question:-

b) List any two values exhibited by the worker. 

Value points:-

• Responsible towards society

• Social awareness

• Ability to take right decision

• Care and concern for others

• Scientific temper

Chemical Kinetics

A child of seven years got fever. He refused to take medicines. His mother crushed the crocin tablet and mixed it with honey and gave it to the child saying its sweet and better.

Contextual questions:-

a) Define rate of reaction and give its SI units. 

b) Which out of the two pill or crushed pill have higher rate of absorption and why?

Value based question:-

c) Which values were kept in mind in this activity? 

Value points:-

• Care and concern

• Awareness of health and hygiene

Electrochemistry

Hydrogen is used as a main source of fuel in a fuel cell as it is renewable and non polluting source of energy. This is the vision of the hydrogen Economy.

Contextual question:-

a) Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

Value based question:-

b) What are the values exhibited in the choice of decision?

Value Points:-

• Concern for environment

• Capability to find alternative resources

• Social responsibility

Solutions

Vinod went to Manali. After reaching there he became weak and unable to think clearly. A stranger took him to the hospital.

Contextual Question:-

a) Name the condition he was suffering from and give the reason. 

Value Based Qustion:-

b) List the values exhibited by the stranger.

Value Points:-

• Compassion

• Concern

• Awareness

• Helpfulness

Chemistry In Everyday Life

Phenelzine is used as an anti-depressant drug for the treatment of stress.

Contextual Question:-

a) How does this drug help in the treatment of stress? 

Value Based Question:-

b) What vales are kept in mind while taking this drug? 

Value Points:-

• Not to become dependent on the drug.

• To be taken only when prescribed by the doctor.

• Use responsibly.

• Look for alternative suitable methods as stress reliever like yoga, medication, etc.

Chemistry In Everyday Life

A dirty cloth was washed with soap in hard water. A gummy mass was formed on the cloth.

Contextual Question:-

a) Why is soap ineffective in washing clothes in hard water? What may be used in place of soap? 

Value Based Question:-

b) What are the values will you keep in mind while using soaps as detergents?

Value Points:-

• Concern for Environment.

• Concern for Aquatic life.

• Avoid wastage.

Haloarenes and Haloalkanes

A number of polyhalogen compounds have many industrial applications. However, some of these compounds cannot be easily decomposed and even cause depletion of ozone layer, so should be used in minimum amounts.

Contextual Question:-

a) Name any four such compounds? 

Value Based Question:-

b) List the values associated with the above decision?

Value Points:-

• Care for environment

• Responsible attitude

Solids

Closed packing of particles results in two highly efficient lattices, HCP and CCP. Both the lattices have packing efficiency 74%. Other type of packing are not close packing and have less efficiency like BCC(68%) and simple unit cell(54%).

Contextual Question:-

a) Calculate the percentage efficiency of a crystal acquired in FCC type unit cell? 

Value Based Question:-

b) How do you correlate the efficiency of human value to crystalline packing efficiency in solids? 

Value Points:-

• Organized Behaviour leads to stability.

• High Efficiency

• Mental Calmer/Satisfaction

 Please click the below link to access CBSE Class 12 Chemistry Value Based Questions