Class 12 Chemistry : Alcohols, Phenols and Ethers
MCQs + Fill in the Blanks + True/False + Assertion Reason + Short Answer + Reaction-Based Questions
SECTION A: Multiple Choice Questions (MCQs)
1. The functional group present in alcohols is:
A) –CHO
B) –OH
C) –COOH
D) –O–
Answer: B) –OH
2. Phenol differs from alcohol because in phenol:
A) Oxygen is absent
B) –OH is attached to aromatic carbon
C) –OH is attached to alkyl carbon
D) It contains no hydrogen bonding
Answer: B) –OH is attached to aromatic carbon
3. The general formula of ethers is:
A) R–OH
B) R–CO–R
C) R–O–R′
D) R–CHO
Answer: C) R–O–R′
4. Which of the following is a primary alcohol?
A) CH₃OH
B) CH₃CHOHCH₃
C) (CH₃)₃COH
D) C₆H₅OH
Answer: A) CH₃OH
5. Which alcohol gives ketone on oxidation?
A) Primary alcohol
B) Secondary alcohol
C) Tertiary alcohol
D) Phenol
Answer: B) Secondary alcohol
6. The correct order of dehydration of alcohols is:
A) 1° > 2° > 3°
B) 3° > 2° > 1°
C) 2° > 1° > 3°
D) 1° > 3° > 2°
Answer: B) 3° > 2° > 1°
7. Phenol is more acidic than ethanol because:
A) Oxygen is absent in phenol
B) Phenoxide ion is resonance stabilised
C) Ethanol has higher molecular mass
D) Phenol cannot lose hydrogen
Answer: B) Phenoxide ion is resonance stabilised
8. The reagent used in Williamson ether synthesis is:
A) Sodium alkoxide
B) Sodium chloride
C) Nitric acid
D) Zinc dust
Answer: A) Sodium alkoxide
9. Hydroboration oxidation of alkenes gives:
A) Markovnikov alcohol
B) Anti-Markovnikov alcohol
C) Ether
D) Aldehyde
Answer: B) Anti-Markovnikov alcohol
10. The catalyst used in industrial preparation of methanol is:
A) ZnO–Cr₂O₃
B) AlCl₃
C) FeCl₃
D) NiCl₂
Answer: A) ZnO–Cr₂O₃
11. Lucas reagent contains:
A) HNO₃ + Zn
B) HCl + ZnCl₂
C) NaOH + Zn
D) H₂SO₄ + NaCl
Answer: B) HCl + ZnCl₂
12. Lucas test is used to distinguish:
A) Aldehydes and ketones
B) Alcohols of different classes
C) Phenols and ethers
D) Acids and bases
Answer: B) Alcohols of different classes
13. Phenol reacts with bromine water to give:
A) Bromobenzene
B) 2,4,6-Tribromophenol
C) Benzene
D) Anisole
Answer: B) 2,4,6-Tribromophenol
14. Kolbe reaction produces:
A) Benzene
B) Salicylic acid
C) Ethanol
D) Acetone
Answer: B) Salicylic acid
15. Reimer–Tiemann reaction introduces:
A) –OH group
B) –CHO group
C) –NO₂ group
D) –COOH group
Answer: B) –CHO group
16. Ether cleavage is mainly done using:
A) NaOH
B) HI
C) NH₃
D) H₂O
Answer: B) HI
17. The major product of anisole nitration is:
A) m-Nitroanisole
B) p-Nitroanisole
C) Benzene
D) Phenol
Answer: B) p-Nitroanisole
18. Methanol is also known as:
A) Grain alcohol
B) Wood spirit
C) Absolute alcohol
D) Rectified spirit
Answer: B) Wood spirit
19. Ethanol is produced industrially by:
A) Oxidation of methane
B) Fermentation of sugars
C) Reduction of benzene
D) Hydrolysis of ethers
Answer: B) Fermentation of sugars
20. The strongest acid among the following is:
A) Ethanol
B) Phenol
C) p-Nitrophenol
D) Methanol
Answer: C) p-Nitrophenol
SECTION B: Fill in the Blanks
1. Alcohols contain the functional group ______.
Answer: –OH
2. Phenol is represented by the formula ______.
Answer: C₆H₅OH
3. Ethers contain oxygen atom between two ______ groups.
Answer: carbon/alkyl
4. Alcohol dehydration produces ______.
Answer: Alkene
5. Primary alcohol oxidation first gives ______.
Answer: Aldehyde
6. Secondary alcohol oxidation gives ______.
Answer: Ketone
7. Phenol reacts with NaOH to form sodium ______.
Answer: phenoxide
8. The industrial method of phenol preparation from cumene gives phenol and ______.
Answer: acetone
9. Williamson synthesis follows ______ mechanism.
Answer: SN2
10. Phenol with bromine water gives ______ precipitate.
Answer: white
11. Methanol poisoning produces ______ acid in the body.
Answer: methanoic
12. Alcohols have high boiling points due to ______ bonding.
Answer: hydrogen
SECTION C: True or False
1. Phenol is less acidic than ethanol.
Answer: False
2. Tertiary alcohols oxidise easily to ketones.
Answer: False
3. Ethers have lower boiling points than alcohols.
Answer: True
4. Williamson synthesis is suitable for primary alkyl halides.
Answer: True
5. –OH group in phenol is meta directing.
Answer: False
6. Hydroboration follows Markovnikov addition.
Answer: False
7. Phenoxide ion is stabilised by resonance.
Answer: True
8. Methanol is poisonous.
Answer: True
SECTION D: Assertion–Reason Questions
1.
Assertion: Phenol is more acidic than alcohol.
Reason: Phenoxide ion is resonance stabilised.
A) Both true and reason explains assertion
B) Both true but reason does not explain assertion
C) Assertion true, reason false
D) Both false
Answer: A
2.
Assertion: Ethers have lower boiling points than alcohols.
Reason: Ethers cannot form intermolecular hydrogen bonding.
Answer: A
3.
Assertion: Tertiary alcohols react faster with Lucas reagent.
Reason: They form stable carbocations.
Answer: A
4.
Assertion: Williamson synthesis is not preferred with tertiary alkyl halides.
Reason: Elimination reaction competes with substitution.
Answer: A
SECTION E: Very Short Answer Questions
1. What is a monohydric alcohol?
Answer:
An alcohol containing one hydroxyl (–OH) group is called monohydric alcohol.
2. Give an example of a secondary alcohol.
Answer:
Propan-2-ol (CH₃CHOHCH₃)
3. Why are alcohols soluble in water?
Answer:
Because they form hydrogen bonds with water molecules.
4. Name the reagent used in Reimer–Tiemann reaction.
Answer:
Chloroform and NaOH.
5. Name the product of Kolbe reaction.
Answer:
Salicylic acid.
6. What is denatured alcohol?
Answer:
Ethanol made unfit for drinking by adding poisonous substances is called denatured alcohol.
SECTION F: Reaction-Based Questions
1. Write the reaction of ethanol with sodium.
Answer:
2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂
2. Write oxidation products of alcohols.
Answer:
Primary alcohol → Aldehyde → Carboxylic acid
Secondary alcohol → Ketone
Tertiary alcohol → Difficult oxidation
3. Write Kolbe reaction.
Answer:
Sodium phenoxide + CO₂ → Salicylic acid (after acidification)
4. Write Reimer–Tiemann reaction product.
Answer:
Phenol + CHCl₃ + NaOH → Salicylaldehyde
5. Write Williamson ether synthesis.
Answer:
RONa + R′X → ROR′ + NaX
SECTION G: Important HOTS Questions
1. Why is phenol acidic but alcohol is weakly acidic?
Answer:
Phenol forms a resonance-stabilised phenoxide ion, whereas alkoxide ion from alcohol is not resonance stabilised.
2. Why does anisole give mainly para substitution?
Answer:
The –OCH₃ group activates the benzene ring and directs electrophiles to ortho and para positions. Para product is less sterically hindered.
3. Why are tertiary alcohols more easily dehydrated?
Answer:
They form more stable tertiary carbocations.
4. Why does ether have lower boiling point than alcohol?
Answer:
Ether molecules cannot form intermolecular hydrogen bonds with each other.
5. Why is Williamson synthesis unsuitable for tertiary alkyl halides?
Answer:
Strong bases cause elimination reactions instead of substitution.