Every Book Back multiple-choice question from Hydroxy Compounds and Ethers (12th Standard Chemistry, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
An alcohol (x) gives blue colour in Victor Meyer’s test and 3.7g of X when treated with metallic sodium liberates 560 mL of hydrogen at 273 K and 1 atm pressure what will be the possible structure of X?
- A. \(CH_3CH(OH)CH_2CH_3\)Correct
- B. \(CH_3-CH(OH)-CH_3\)
- C. \(CH_3C(OH)(CH_3)_2\)
- D. \(CH_3-CH_2-CH(OH)-CH_2-CH_3\)
Explanation. A blue color in the Victor Meyer test indicates a secondary alcohol. Calculations based on molar mass and hydrogen evolution confirm the structure matches a four-carbon secondary alcohol, butan-2-ol.
Q2
Which of the following compounds on reaction with methyl magnesium bromide will give tertiary alcohol.
- A. benzaldehyde
- B. propanoic acid
- C. methyl propanoateCorrect
- D. acetaldehyde
Explanation. Esters like methyl propanoate react with two equivalents of a Grignard reagent to produce tertiary alcohols. Aldehydes in the other options react with Grignard reagents to produce secondary alcohols.
Q3
In the reaction sequence, Ethene \(\xrightarrow{HOCl}\) A \(\xrightarrow{X}\) ethan -1, 2 - diol. A and X respectively are
- A. Chloroethane and \(NaOH\)
- B. ethanol and \(H_2SO_4\)
- C. 2-chloroethan-1-ol and \(NaHCO_3\)Correct
- D. ethanol and \(2H_2O\)
Explanation. Ethene reacts with hypochlorous acid to form ethylene chlorohydrin (A). Subsequent hydrolysis using sodium bicarbonate (X) replaces the chlorine with a hydroxyl group to form ethylene glycol.
Q4
Which one of the following is the strongest acid
- A. 2-nitrophenol
- B. 4-chlorophenol
- C. 4-nitrophenolCorrect
- D. 3-nitrophenol
Explanation. 4-nitrophenol is the strongest acid because the nitro group at the para position stabilizes the phenoxide ion through both strong inductive and resonance effects.
Q5
Carbolic acid is
- A. PhenolCorrect
- B. Picric acid
- C. benzoic acid
- D. phenylacetic acid
Explanation. Phenol is commonly known by its traditional name, carbolic acid.
Q6
Which one of the following will react with phenol to give salicyladehyde after hydrolysis.
- A. Dichloro methane
- B. trichloroethane
- C. trichloro methaneCorrect
- D. \(CO_2\)
Explanation. Salicylaldehyde is produced from phenol via the Reimer-Tiemann reaction, which utilizes trichloromethane (chloroform) and an aqueous base.
Q7
\((CH_3)_3 - C - CH(OH) CH_3 \xrightarrow{Con H_2SO_4} X\) (major product)
- A. \((CH_3)_3 CCH = CH_2\)
- B. \((CH_3)_2 C = C (CH_3)_2\)Correct
- C. \(CH_2 = C(CH_3)CH_2 - CH_2 - CH_3\)
- D. \(CH_2 = C (CH_3) - CH_2 - CH_2 - CH_3\)
Explanation. Dehydration of this secondary alcohol involves the formation of a carbocation that undergoes a 1,2-methyl shift to form a more stable tertiary carbocation, resulting in tetramethylethylene.
Q8
Assertion : Phenol is more acidic than ethanol
Reason: Phenoxide ion is resonance stabilized
- A. both assertion and reason are true and reason is the correct explanation of assertion.Correct
- B. both assertion and reason are true but reason is not the correct explanation of assertion.
- C. assertion is true but reason is false
- D. both assertion and reason are false.
Explanation. Phenol is significantly more acidic than ethanol because the negative charge on the phenoxide ion is delocalized through resonance within the benzene ring, stabilizing the conjugate base.
Q9
In the reaction Ethanol \(X \xrightarrow{PCl_5} Y \xrightarrow{alc.KOH} Z \xrightarrow{H_2SO_4/H_2O, 298K}\). The 'Z' is
- A. ethane
- B. ethoxyethane
- C. ethylbisulphite
- D. ethanolCorrect
Explanation. Ethanol reacts with phosphorus pentachloride to form ethyl chloride, which undergoes dehydrohalogenation to ethene. Subsequent hydration of ethene in an acidic medium regenerates ethanol.
Q10
Isopropylbenzene on air oxidation in the presence of dilute acid gives
- A. \(C_6H_5COOH\)
- B. \(C_6H_5COCH_3\)
- C. \(C_6H_5COC_6H_5\)
- D. \(C_6H_5-OH\)Correct
Explanation. The cumene process involves the oxidation of isopropylbenzene to cumene hydroperoxide, which is then decomposed by dilute acid to yield phenol and acetone as a byproduct.
Q11
Assertion : Phenol is more reactive than benzene towards electrophilic substitution reaction
Reason : In the case of phenol, the intermediate arenium ion is more stabilized by resonance.
- A. if both assertion and reason are true and reason is the correct explanation of assertion.Correct
- B. if both assertion and reason are true but reason is not the correct explanation of assertion.
- C. assertion is true but reason is false
- D. both assertion and reason are false.
Explanation. The hydroxyl group is an activating group that increases electron density on the benzene ring, and resonance stabilization of the intermediate cation further lowers the activation energy.
Q12
\(HO CH_2 CH_2 – OH\) on heating with periodic acid gives
- A. methanoic acid
- B. Glyoxal
- C. methanalCorrect
- D. \(CO_2\)
Explanation. Periodic acid acts as a specific oxidizing agent that cleaves the carbon-carbon bond in vicinal diols, such as ethylene glycol, converting both primary alcohol groups into methanal.
Q13
Which of the following compound can be used as artifreeze in automobile radiators?
- A. methanol
- B. ethanol
- C. Neopentyl alcohol
- D. ethan -1, 2-diolCorrect
Explanation. Ethylene glycol, also known as ethan-1,2-diol, is used as an antifreeze because it is miscible with water and significantly lowers its freezing point.
Q14
One mole of an organic compound (A) with the formula \(C_3H_8O\) reacts completely with two moles of HI to form X and Y. When Y is boiled with aqueous alkali it forms Z. Z answers the iodoform test. The compound (A) is
- A. propan – 2-ol
- B. propan -1-ol
- C. ethoxy ethane
- D. methoxy ethaneCorrect
Explanation. Methoxyethane reacts with excess HI to yield methyl iodide and ethyl iodide. Boiling ethyl iodide with aqueous alkali produces ethanol, which contains the specific group required for the iodoform test.
Q15
Williamson synthesis of preparing dimethyl ether is a / an /
- A. \(S_N1\) reactions
- B. \(S_N2\) reactionCorrect
- C. electrophilic addition
- D. electrophilic substitution
Explanation. This synthesis proceeds through a bimolecular nucleophilic substitution mechanism where the alkoxide ion attacks the primary alkyl halide in a single concerted step.
Q16
On reacting with neutral ferric chloride, phenol gives
- A. red colour
- B. violet colourCorrect
- C. dark green colour
- D. no colouration.
Explanation. Phenol reacts with ferric chloride solution to form a ferric-phenoxide complex, which results in a characteristic violet coloration used for identification.
