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Class 12 Chemistry  MCQ Questions of Aldehydes, Ketones and Carboxylic Acids with Answers?

Answer 1

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1. The oxidation of toluene to benzaldehyde by chromyl, chloride is called

(a) Etard reaction
(b) Riemer-Tiemann reaction
(c) Wurtz reaction
(d) Cannizzaro’s reaction

2. The addition of HCN to carbonyl compounds is an example of

(a) nucleophilic addition
(b) electrophilic addition
(c) free radical addition
(d) electromeric addition

3. Aldehydes other than formaldehyde react with Grignard’s reagent to give addition products which on hydrolysis give

(a) tertiary alcohols
(b) secondary alcohols
(c) primary alcohols
(d) carboxylic acids

4. Which of the following will not give aldol condensation?

(a) Phenyl acetaldehyde
(b) 2-Methylpentanal
(c) Benzaldehyde
(d) 1-Phenylpropanone

5. Benzoyl Chloride on reduction with H₂/ Pd-BaSO₄ produces

(a) benzoic acid
(b) benzyl alochol
(c) benzoyl sulphate
(d) benzaldehyde

6. What is the test to differentiate between penta-2-one and pentan-3-one?

(a) Iodoform test
(b) Benedict’s test
(c) Fehling’s test
(d) Aldol condensation test

7. Which of the following does not undergo Cannizzarro’s reaction?

(a) Benzaldehyde
(b) 2-Methylpropanal
(c) p-Methoxybenzaldehyde
(d) 2, 2-Dimethylpropanal

8. Which among the following is most reactive to give nucleophilic addition?

(a) FCH₂CHO
(b) ClCH₂CHO
(c) BrCH₂CHO
(d) ICH₂CHO

9. Which compound is obtained when acetaldehydes are treated with dilute solution of caustic soda?

(a) Sodium acetate
(b) Resinous mass
(c) Aldol
(d) Ethyl acetate

10. Which of the following forces explain the boiling point of aldehydes and ketones?

(a) Hydrogen bonding
(b) van der Waal’s forces
(c) Dipole-dipole attraction
(d) None of these

11.  Acetaldehyde reacts with

(a) Electrophiles only
(b) Nucleophiles only
(c) Free radicals only
(d) Both electrophiles and nucleophiles

12. If formaldehyde and KOH are heated, then we get

(a) methane
(b) methyl alcohol
(c) ethyl formate
(d) acetylene

13. Schiff’s reagent gives pink colour with

(a) acetaldehyde
(b) acetone
(c) acetic acid
(d) methyl acetate

14. The IUPAC name of CH₃COCH(CH₃)₂ is

(a) 2-methyl-3-butanone
(b) 4-methylisopropyl ketone
(c) 3-methyl-2-butanone
(d) Isopropylmethyl ketone

15. IUPAC name of ethyl isopropyl ketone is

(a) 4-methyl pent-3-one
(b) 2-methyl pent-3-one
(c) 4-methyl pent-2-one
(d) 2-methyl pent-2-one

16. The π-bond in carbonyl group is formed by

(a) s-s-overlapping
(b) p-p-overlapping
(c) s-p-overlapping
(d) p-d-overlapping

17. Which of the following have pleasant smell?

(a) Methanal
(b) Propanal
(c) Ethanal
(d) Hexanal

18. Which one of the following can be oxidised to the corresponding carbonyl compound?

(a) 2-hydroxy-propane
(b) Ortho-nitrophenol
(c) Phenol
(d) 2-methyl-2 hydroxy-propane

19. The catalyst used in Rosenmund's reduction is

(a) HgSO₄
(b) Pd/BaSO₄
(c) anhydrous AlCl₃
(d) anhydrous ZnCl₂

20. Vinegar is a solution of acetic acid which is :

(a) 15–20%
(b) 20 –25%
(c) 6 – 8%
(d) 2 – 4%

21. Acetone reacts with iodine (I₂) to form iodoform in the presence of

(a) CaCO₃
(b) NaOH
(c) KOH
(d) MgCO₃

22. When acetaldehyde is heated with Fehling’s solution it gives a precipitate of

(a) Cu
(b) CuO
(c) Cu₂O
(d) Cu(OH)₂

23. Aldehydes and ketones are distinguished by which of the following test?

(a) Lucas test
(b) Tollen’s test
(c) KMnO₄ solution (Baeyer’s test)
(d) None of these

24. What is formed when a primary alcohol undergoes catalytic dehydrogenation?

(a) Aldehyde
(b) Ketone
(c) Alkene
(d) Acid

25. The reagent used for the separation of acetaldehyde from acetophenone is

(a)  NaHSO₃
(b)  C₆H₅NHNH₂
(c)  NH₂OH
(d)  NaOH and I₂

Answer 2

1. Answer : (a) Etard reaction

Explanation: Thus, oxidation of toluene to benzaldehyde by the use of chromyl chloride is called Etard's reaction.

2. Answer : (a) nucleophilic addition

Explanation: The reaction of HCN with carbonyl compounds is an example of the nucleophilic addition reaction.

3. Answer : (b) secondary alcohols

Explanation: aldehydes other than formaldehyde react with Grignard's reagent to give additional products which on hydrolysis give secondary alcohols.

4. Answer : (c) Benzaldehyde

Explanation: Benzaldehyde will not give aldol condensation due to absence of \(\alpha\)-H atom.

5. Answer : (d) benzaldehyde

Explanation: Benzoyl chloride on reduction with hydrogen in the presence of Pd and `BaSO₄ gives acetophenone/ benzaldehyde.

6. Answer : (a) Iodoform test

Explanation: Iodoform test is performed to differentiate between pentan-2-one and pentan-3-one.

7. Answer : (b) 2-Methylpropanal

Explanation: The alpha carbon i.e., the carbon atom adjacent to the carbonyl group is connected to three methyl groups and no hydrogen atom is bonded to it. Thus, the compound has no alpha hydrogen and can undergo a Cannizzaro reaction. Hence, the compound which cannot undergo a Cannizzaro reaction is 2-methylpropanal.

8. Answer : (a) FCH₂CHO

Explanation: FCH₂CHO is most reactive towards nucleophilic addition since presence of most electrophilic addition since presence of most electronegative F withdraws electrons from carbon of carbonyl group making it more polar.

9. Answer : (c) Aldol

Explanation: Aldehyde and ketones which have at least one \(\alpha\)-hydrogen atom are known to react with dilute aqueous caustic soda. As a result, they produce \(\alpha\)-hydroxy aldehydes. These compounds are known as aldols and reaction is known as aldol reaction.

10. Answer : (c) Dipole-dipole attraction

Explanation: The boiling point of molecules depends on the intermolecular force of attraction, stronger the force, higher is the boiling point. Boiling points of aldehydes and ketone depend on intermolecular dipole-dipole attraction. This is because of electronegative oxygen attached to the carbon atom.

11. Answer : (b) Nucleophiles only

Explanation: The carbonyl group is highly reactive polar group. It is polarised due to the higher electronegativity of oxygen in comparison to carbon. As a result, the electrons present between carbon and oxygen are more attracted towards oxygen atom. The actual structure may be represented as Consequently, the carbonyl carbon is positively charged while the oxygen is negatively charged. The positively charged carbon is easily attacked by a nucleophilic reagent (Nu^-).

12. Answer : (b) methyl alcohol

Explanation: When \(\alpha\)-hydrogen is absent in carbonyl group, those compound gives cannizaro reaction. This reaction show disproportionation. The oxidation product is salt of carboxylic acid and reduced product is alcohol.

HCHO + HCHO → CH₃OH + HCOO⁻K⁺

13. Answer : (a) acetaldehyde

Explanation: Schiff's reagent is used to detect the presence of aldehydic and ketonic group. It consists of fuchsin dye decolourised by sulphurous acid. Immediate red/pink colour appearance detects the presence of aliphatic aldehyde. Aliphatic ketone and aromatic aldehydes takes time and slowly pink colour blooms.

14. Answer : (a) 2-methyl-3-butanone

Explanation: The IUPAC name of CH₃COCH(CH₃)₂ (c) 3-methyl-2-butanone.

15. Answer: (b) 2-methyl pent-3-one

Explanation: The IUPAC name of ethyl isopropyl ketone is 2-methyl-3-pentanone.

16. Answer: (b) p-p-overlapping

Explanation: π bonds are formed by the sidewise or lateral overlapping of p orbitals. Where, as σ bonds are formed by axial overlapping of molecular orbitals.

17. Answer: (d) Hexanal

Explanation: Hexanal, also called hexanaldehyde or caproaldehyde is an alkyl aldehyde used in the flavor industry to produce fruity flavors. Its scent resembles freshly cut grass, like cis-3-hexenal. It is potentially useful as a natural extract that prevents fruit spoilage.

18. Answer: (a) 2-hydroxy-propane

Explanation: 2-hydroxy propane or secondary alcohol is oxidised into propanone (corresponding because in 2-hydroxy propane, secondary alcoholic group is present and it is oxidised into ketone).

19. Answer: (b) Pd/BaSO₄

Explanation: The reaction, a hydrogenolysis, is catalysed by palladium on barium sulfate, which is sometimes called the Rosenmund catalyst. Barium sulfate has a low surface area which reduces the activity of the palladium, preventing over-reduction.

20. Answer: (c) 6 – 8%

Explanation: An aqueous of acetic acid is called vinegar which contains 5-8% acetic acid. Vinegar is a solution of 5-8% acetic acid in water, that's why it is aqueous (containing water) solution of 5%-8% of acetic acid. Other names are Ethanoic acid or Methane carboxylic acid.

21. Answer: (b) NaOH

Explanation: CH₃COCH₃ + 3I₂ + 4NaOH → CHI₃ + 3Na + CH₃COONa + 3H₂O

22. Answer: (c) Cu₂O

Explanation: The precipitate formed is red in colour and is only given when Fehling's test is done for aldehyde. Thus, the red precipitate formed when Fehling's solution reacts with aldehyde is Cu₂O.

23. Answer: (b) Tollen’s test

Explanation: Tollens' test, also known as silver-mirror test, is a qualitative laboratory test used to distinguish between an aldehyde and a ketone. It exploits the fact that aldehydes are readily oxidized.

24. Answer: (a) Aldehyde

Explanation: Primary alcohols get dehydrogenated with reduced copper at 573K, to give corresponding aldehydes.

25. Answer: (a)  NaHSO₃

Explanation: 

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