CBSE Class 12 Chemistry Aldehydes Ketones and Carboxylic Acids MCQs Set F

Question. Among the following acids which has the lowest pKa value?
(a) CH₃CH₂COOH
(b) (CH₃)₂CH — COOH
(c) HCOOH
(d) CH₃COOH
Answer: c

Question. Boiling points of carboxylic acids are
(a) lower than corresponding alcohols
(b) higher than corresponding alcohols
(c) equal to that of corresponding alcohols
(d) None of the above
Answer: b

Question. Toluene can be oxidised to benzoic acid by
(a) KMnO₄ (alk.)
(b) K₂Cr₂O₇ (alk.)
(c) Both (a) and (b)
(d) Neither (a) nor (b)
Answer: a

Question. Which of the following compounds will give butanone on oxidation with alkaline KMnO₄ solution?
(a) Butan-1-ol
(b) Butan-2-ol
(c) Both of these
(d) None of these
Answer: b

Question. Two compounds benzyl alcohol and benzoic acid are formed from this compound, when this compound is heated in the presence of conc.NaOH, this compound is.
(a) Benzaldehyde
(b) Benzylalcohol
(c) Acetophenone
(d) Benzophenone
Answer: a

Question. Which is false in case of carboxylic acids?
(a) They are polar molecules
(b) They form H-bonds
(c) They are stronger than mineral acids
(d) They have higher b.p. than corresponding alcohols
Answer: c

Question. The major product of nitration of benzoic acid is
(a) 3- Nitrobenzoic acid
(b) 4- Nitrobenzoic acid
(c) 2- Nitrobenzoic acid
(d) 2, 4- dinitrobenzoic acid
Answer: a

Question. The reaction of carboxylic acid gives effervescences of CO₂ with NaHCO₃. The CO₂ comes from.
(a) R – COOH
(b) NaHCO₃
(c) Both (a) and (b)
(d) None of these
Answer: b

 Question. In the anion HCOO– the two carbon-oxygen bonds are found to be of equal length. What is the reason for it?
(a) Electronic orbitals of carbon atom are hybridised
(b) The C=O bond is weaker than the C–C bond
(c) The anion HCOO– has two reasonating structures
(d) The anion is obtained by removal of a proton from the acid molecule
Answer: c

Question.The strongest acid among the following is –
(a) Salicylic acid
(b) m-hydroxybenzoic acid
(c) p-hydroxybenzoic acid
(d) Benzoic acid
Answer: a

Question. Dimerisation of carboxylic acids is due to
(a) ionic bond
(b) covalent bond
(c) coordinate bond
(d) intermolecular hydrogen bond
Answer: d

Question. Acetic anhydride is obtained by the reaction of
(a) sodium and acetic acid
(b) ammonia and acetic acid
(c) ethanol and acetic acid
(d) P₂O₅ and acetic acid
Answer: d

Question. Among the following, the most acidic is :
(a) CH₃COOH
(b) ClCH₂COOH
(c) Cl₂CHCOOH
(d) Cl₂CHCH₂COOH
Answer: c

Question. Wolf-Kishner reduction is
(a) reduction of carbonyl compound into alcohol
(b) reduction of carbonyl compound into alkene
(c) reduction of carboxyl compound into alkane
(d) reduction of nitro compound into aniline
Answer: c

Question. Select the acid(s) which cannot be prepared by Grignard reagent.
(a) Acetic acid
(b) Succinic acid
(c) Formic acid
(d) All of the above
Answer: c

Question. Carboxylic acids are more acidic than phenol and alcohol because of
(a) intermolecular hydrogen bonding
(b) formation of dimers
(c) highly acidic hydrogen
(d) resonance stabilization of their conjugate base
Answer: d

Question. A carboxylic acid can best be converted into acid chloride by using
(a) PCl₅
(b) SOCl₂
(c) HCl
(d) ClCOCOCl
Answer: d

Question. The elimination of CO₂ from a carboxylic acid is known as
(a) hydration
(b) dehydration
(c) decarboxylation
(d) carboxylation
Answer: c

Question. Which reaction is used for detecting the presence of carbonyl group?
(a) Reaction with hydrazine
(b) Reaction with phenyl hydrazine
(c) Reaction with hydroxylamine
(d) All of the above
Answer: d

Question. Which of the following acids has the smallest dissociation constant ?
(a) CH₃CHFCOOH
(b) FCH₂CH₂COOH
(c) BrCH₂CH₂COOH
(d) CH₃CHBrCOOH
Answer: c

Question. Benzoic acid reacts with conc. HNO₃ and H₂SO₄ to give :
(a) 3-Nitrobenzoic acid
(b) 4-Benzene sulphonic acid
(c) 4-Nitrobenzoic acid
(d) 2-Nitrobenzoic acid
Answer: a

Question. Lower carboxylic acids are soluble in water due to
(a) low molecular weight
(b) hydrogen bonding
(c) dissociation into ions
(d) easy hydrolysis
Answer: b

STATEMENT TYPE QUESTIONS

Question. Read the following statements and choose the correct option
(i) The boiling points of aldehydes and ketones are lower than those of alcohols of similar molecular masses
(ii) Alcohols show intermolecular hydrogen bonding whereas aldehydes and ketones do not show intermolecular hydrogen bonding.
(iii) The lower members of aldehydes and ketones are miscible with water in all proportions, because they form hydrogen bond with water.
(iv) The solubility of aldehydes and ketones increases rapidly on increasing the length of alkyl chain
(a) TTFF
(b) TFFT
(c) FTTT
(d) TTTF
Answer: d

Question. Aldehydes are generally more reactive than ketones in nucleophilic addition reactions. Which of the following statements accounts for this ?
(i) Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon
(ii) Aldehydes show resonance whereas ketones do not
(iii) Electronically, the presence of two alkyl groups reduce the electrophilicity of the carbonyl carbon more effectively.
(iv) Electronically carbonyl carbon atom in ketones is more electrophilic than in aldehydes
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
Answer: a

Question. Read the following statements and choose the correct option
(i) The carbonyl carbon atom is sp² -hybridised
(ii) The carbonyl carbon is an electrophilic (Lewis acid) centre
(iii) The carbonyl oxygen is a nucleophilic (Lewis base) centre
(iv) Carbonyl compounds are non- polar in nature.
(a) (i), (ii) and (iv) are correct
(b) (i), (ii) and (iii) are correct
(c) (ii), (iii) and (iv) are correct
(d) (ii) and (iv) are correct
Answer: b

Question. Which of the following statement(s) is/are true regarding esterification of a carboxylic acid with an alcohol ?
(i) It is carried out in presence of a strong acid which acts as a catalyst.
(ii) The strong acid makes the carbonyl carbon more electrophilic, and hence causes the alcohol, a strong nucleophile to attack on the carbonyl carbon.
(iii) The strong acid makes the carbonyl group more electrophilic which is thus attacked easily by an alcohol, a weak nucleophile.
(iv) Esterification can be done even in absence of a strong acid.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (i) only
(d) (iv) only
Answer: b

Question. Which of the following statement(s) is/are true regarding preparation of aldehydes and ketones?
(i) Both can be prepared by the oxidation of the concerned alcohol with copper at about 250ºC.
(ii) Both can be prepared by the oxidation of the concerned alcohol by Oppenauer oxidation.
(iii) Both can be prepared by the oxidation of respective alcohol with acidic dichromate.
(a) (i) only
(b) (ii) and (iii)
(c) (i) and (iii)
(d) All the three
Answer: a

Question. Which of the following statements are false?
(i) No aldehyde can be prepared by the oxidation of primary alcohol with acidic KMnO₄.
(ii) Aldehydes having a boiling point less than 100°C can be prepared by the oxidation of primary alcohol with acidic dichromate.
(iii) Secondary alcohols on oxidation with PCC in dichloromethane give carboxylic acids having lesser number of carbon atoms
(iv) Tertiary alcohols can’t be oxidised at all
(a) (ii) and (iii)
(b) (ii), (iii) and (iv)
(c) (i), (iii) and (iv)
(d) (i), (ii) and (iii)
Answer: c

Question. (i) Give reasons :
(a) HCHO is more reactive than CH₃ – CHO towards addition of HCN.
(b) pKa of O₂N – CH₂ – COOH is lower than that of CH₃ – COOH.
(c) Alpha hydrogen of aldehydes and ketones is acidic in nature.
(ii) Give simple chemical tests to distinguish between the following pairs of compounds :
(a) Ethanal and Propanal
(b) Pentan-2-one and Pentan-3-one
Answer. (i) (a) Due to +I effect of methyl group in CH₃CHO. 
(b) Due to –I effect of nitro group in nitroacetic acid. 
(c) Due to the strong electron withdrawing effect of the carbonyl group and resonance stabilisation of the conjugate base. 
(ii) (a) Add NaOH and I₂ to both the compounds and heat, ethanal gives yellow ppt of iodoform. 
(b) Add NaOH and I₂ to both the compounds and heat, pentan-2-one gives yellow ppt of iodoform.