Q.1 Which of the following compounds is an aldehyde?
CH3CH2OH
CH3CHO
CH3COCH3
CH3COOH
Explanation - CH3CHO is ethanal, which contains the -CHO functional group characteristic of aldehydes.
Correct answer is: CH3CHO
Q.2 Which reagent is commonly used to distinguish aldehydes from ketones?
Tollens' reagent
Bromine water
NaOH
H2SO4
Explanation - Tollens' reagent (Ag(NH3)2+) oxidizes aldehydes to carboxylic acids, producing a silver mirror, but does not react with ketones.
Correct answer is: Tollens' reagent
Q.3 What is the IUPAC name of CH3COOH?
Methanoic acid
Ethanoic acid
Propanic acid
Acetone
Explanation - CH3COOH has two carbon atoms and a carboxyl (-COOH) group; hence it is named ethanoic acid.
Correct answer is: Ethanoic acid
Q.4 Which of the following undergoes nucleophilic addition reaction?
Benzene
CH3COCH3
CH3CH2OH
CH4
Explanation - Ketones and aldehydes have a polar C=O bond which allows nucleophiles to attack the carbon atom, leading to nucleophilic addition.
Correct answer is: CH3COCH3
Q.5 Which of the following reactions is used to prepare aldehydes from primary alcohols?
Cannizzaro reaction
Oxidation with PCC
Aldol condensation
Reduction with LiAlH4
Explanation - PCC (Pyridinium chlorochromate) selectively oxidizes primary alcohols to aldehydes without further oxidation to carboxylic acids.
Correct answer is: Oxidation with PCC
Q.6 Which of the following acids is aromatic?
Formic acid
Acetic acid
Benzoic acid
Propionic acid
Explanation - Benzoic acid contains a benzene ring attached to the carboxyl group, making it aromatic.
Correct answer is: Benzoic acid
Q.7 What is the product of oxidation of a secondary alcohol?
Aldehyde
Ketone
Carboxylic acid
Alcohol
Explanation - Secondary alcohols oxidize to ketones, whereas primary alcohols oxidize to aldehydes or further to carboxylic acids.
Correct answer is: Ketone
Q.8 Which of the following compounds gives a positive Fehling’s test?
CH3CH2CHO
CH3COCH3
CH3OH
CH3COOH
Explanation - Aldehydes (except aromatic aldehydes) reduce Fehling’s solution to give a brick-red precipitate of Cu2O, whereas ketones do not react.
Correct answer is: CH3CH2CHO
Q.9 Which functional group is present in ketones?
-OH
-CHO
-CO-
-COOH
Explanation - Ketones have the carbonyl group (C=O) bonded to two carbon atoms (-CO-).
Correct answer is: -CO-
Q.10 Which compound reacts with NaHCO3 to release CO2?
Acetone
Formic acid
Acetic acid
Benzaldehyde
Explanation - Carboxylic acids react with sodium bicarbonate to produce carbon dioxide, water, and a salt.
Correct answer is: Acetic acid
Q.11 Which of the following undergoes Cannizzaro reaction?
Formaldehyde
Acetone
Ethanol
Acetic acid
Explanation - Aldehydes without α-hydrogen atoms, like formaldehyde, undergo disproportionation in the Cannizzaro reaction.
Correct answer is: Formaldehyde
Q.12 Which reagent is used to convert aldehydes to alcohols?
NaBH4
PCC
HNO3
Br2
Explanation - Sodium borohydride (NaBH4) is a mild reducing agent that reduces aldehydes to primary alcohols.
Correct answer is: NaBH4
Q.13 What type of reaction is the formation of an acetal from an aldehyde?
Oxidation
Nucleophilic addition
Condensation
Substitution
Explanation - Aldehydes react with alcohols to form acetals through condensation reactions in the presence of an acid catalyst.
Correct answer is: Condensation
Q.14 Which of the following compounds is more acidic?
CH3COOH
CH3CH2OH
CH3CHO
CH3COCH3
Explanation - Carboxylic acids are more acidic due to resonance stabilization of their conjugate base.
Correct answer is: CH3COOH
Q.15 Which reaction involves the cleavage of a C-C bond adjacent to the carbonyl group?
Aldol condensation
Baeyer-Villiger oxidation
Haloform reaction
Cannizzaro reaction
Explanation - The haloform reaction cleaves the C-C bond adjacent to a methyl ketone, producing a haloform and a carboxylate ion.
Correct answer is: Haloform reaction
Q.16 Which of the following is the product when acetaldehyde undergoes aldol condensation?
CH3CH=CHCHO
CH3CH2CHO
CH3CH(OH)CH2CHO
CH3COCH3
Explanation - In aldol condensation, two molecules of aldehyde react to form a β-hydroxyaldehyde (CH3CH(OH)CH2CHO).
Correct answer is: CH3CH(OH)CH2CHO
Q.17 Which of the following carboxylic acids is the strongest?
Formic acid
Acetic acid
Propionic acid
Butyric acid
Explanation - Formic acid has the least alkyl substituents, which stabilizes the conjugate base less, making it more acidic than other carboxylic acids.
Correct answer is: Formic acid
Q.18 Which compound reacts with 2,4-dinitrophenylhydrazine to give a yellow/orange precipitate?
Ethanol
Acetone
Methane
Acetic acid
Explanation - Carbonyl compounds (aldehydes and ketones) react with 2,4-DNPH to form hydrazones, giving yellow/orange precipitates.
Correct answer is: Acetone
Q.19 Which of the following gives a blue precipitate with Schiff’s reagent?
Acetone
Benzaldehyde
Acetic acid
Methanol
Explanation - Aldehydes react with Schiff’s reagent to give a violet or magenta color, indicating the presence of -CHO group.
Correct answer is: Benzaldehyde
Q.20 Which compound cannot undergo oxidation under mild conditions?
Methanol
Ethanol
Acetone
Propanal
Explanation - Ketones generally resist oxidation under mild conditions due to the lack of a hydrogen atom attached to the carbonyl carbon.
Correct answer is: Acetone
Q.21 Which of the following is a β-hydroxy acid?
CH3CH(OH)COOH
CH3CH2COOH
CH3COOH
CH3CH2CH2COOH
Explanation - A β-hydroxy acid has a hydroxyl group on the β-carbon relative to the carboxyl group. CH3CH(OH)COOH satisfies this structure.
Correct answer is: CH3CH(OH)COOH
Q.22 Which of the following is formed when an aldehyde is reduced with LiAlH4?
Primary alcohol
Secondary alcohol
Ketone
Carboxylic acid
Explanation - Aldehydes are reduced to primary alcohols using LiAlH4, a strong reducing agent.
Correct answer is: Primary alcohol
Q.23 Which reaction is used to distinguish between acetone and propanal?
Iodoform test
Bromine test
Lucas test
Tollens' test
Explanation - Acetone gives a positive iodoform test due to the presence of a methyl ketone group, whereas propanal does not.
Correct answer is: Iodoform test
Q.24 Which reagent can convert a ketone to a carboxylic acid?
KMnO4
LiAlH4
NaBH4
PCC
Explanation - Strong oxidizing agents like potassium permanganate (KMnO4) can oxidize ketones, especially methyl ketones, to carboxylic acids.
Correct answer is: KMnO4