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

Question. A compound (X) having molecular formula C₄H₈O₂ is hydrolysed by water in presence of an acid to give a carboxylic acid (Y) and an alcohol (Z). (Z) on oxidation with chromic acid gives (Y).(X), (Y) and (Z) are
            X                     Y                  Z
(a) CH₃COOCH₃       CH₃COOH        CH₃OH
(b) CH₃COOC₂H₅     CH₃COOH        C₂H₅OH
(c) C₂H₅COOCH₃     C₂H₅COOH       C₂H₅OH
(d) CH₃COOC₂H₅     C₂H₅COOH       CH₃OH
Answer: b

Question. a-Hydroxypropanoic acid can be prepared from ethanal by following the steps given in the sequence.
(a) Treat with HCN followed by acidic hydrolysis.
(b) Treat with NaHSO₃ followed by reaction with Na₂CO₃.
(c) Treat with H₂SO₄ followed by hydrolysis.
(d) Treat with K₂Cr₂O₇ in presence of sulphuric acid.
Answer: a

 Question. Carboxylic acids do not undergo Friedel Craft’s reaction because
(a) —COOH group is meta directing
(b) —COOH group is resonance stabilised
(c) carboxyl group is deactivating and gets bonded to Friedel Craft’s catalyst
(d) all of above.
Answer: c

Question. Which of the following statements is incorrect?
(a) FeCl₃ is used in the detection of phenols.
(b) Fehling solution is used in the detection of glucose.
(c) Tollens’ reagent is used in the detection of unsaturation.
(d) NaHSO₃ is used in the detection of carbonyl compounds.
Answer: c

Question. Hydrocarbons are formed when aldehydes and ketones are reacted with amalgamated zinc and conc. HCl. The reaction is called
(a) Cannizzaro reaction
(b) Clemmensen reduction
(c) Rosenmund reduction
(d) Wolff-Kishner reduction.
Answer: b

Question. Which among the following is most reactive to give nucleophilic addition?
(a) FCH₂CHO
(b) ClCH₂CHO
(c) BrCH₂CHO
(d) ICH₂CHO
Answer: a

 Question. Propanal on treatment with dilute sodium hydroxide gives
(a) CH₃CH₂CH₂CH₂CH₂CHO
(b) CH₃CH₂CH(OH)CH₂CH₂CHO
(c) CH₃CH₂CH(OH)CH(CH₃)CHO
(d) CH₃CH₂COOH
Answer: c

Question. To differentiate between pentan-2-one and pentan-3-one a test is carried out. Which of the following is the correct answer?
(a) Pentan-2-one will give silver mirror test
(b) Pentan-2-one will give iodoform test.
(c) Pentan-3-one will give iodoform test
(d) None of these.
Answer: b

Question. An organic compound of molecular formula C₃H₆O did not give a silver mirror with Tollen’s reagent but gave an oxime with hydroxylamine.
It may be
(a) CH₂==CH—CH₂—OH
(b) CH₃COCH₃
(c) CH₃CH₂CHO
(d) CH₂==CH—OCH₃
Answer: b

Question. Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions.
Ethanal, Propanal, Propanone, Butanone
(a) Butanone < Propanone < Propanal < Ethanal
(b) Propanone < Butanone < Ethanal > Propanal
(c) Propanal < Ethanal < Propanone < Butanone
(d) Ethanal < Propanal < Propanone < Butanone
Answer: a

Question. A ketone ‘A’ (C4H8O), which undergoes a haloform reaction, gives a compound ‘B’ on reduction. ‘B’ on heating with sulphuric acid gives a compound ‘C’ which forms mono-ozonide
‘D’. ‘D’ on hydrolysis with zinc dust gives only, ‘E’.
Identify the correct statement.
(a) A is butan-2-one; B is butan-2-ol.
(b) B is but-2-ene; C is acetaldehyde.
(c) D is acetaldehyde; E is butan-2-ol.
(d) B is butan-1-one; D is but-2-ene.
Answer: a

Question. Which of the following compounds will undergo Cannizzaro reaction?
(a) CH₃CHO
(b) CH₃COCH₃
(c) C₆H₅CHO
(d) C₆H₅CH₂CHO
Answer: c

Question. What happens when a carboxylic acid is treated with lithium aluminium hydride?
(a) Aldehyde is formed.
(b) Primary alcohol is formed.
(c) Ketone is formed.
(d) Grignard reagent is formed.
Answer: b

Question. What are the correct steps to convert acetaldehyde to acetone?
(a) CH₃MgBr, H₂O, Oxidation
(b) Oxidation, Ca(OH)₂, Heat
(c) Reduction, KCN, Hydrolysis
(d) Oxidation, C₂H₅ONa, Heat
Answer: b

 Question. Propanone can be prepared from ethyne by
(a) passing a mixture of ethyne and steam over a catalyst, magnesium at 420°C
(b) passing a mixture of ethyne and ethanol over a catalyst zinc chromite
(c) boiling ethyne with water and H₂SO₄
(d) treating ethyne with iodine and NaOH.
Answer: a

Question. Write the IUPAC name of Ph – CH = CH – CHO. 
Answer. IUPAC name : 3-phenylprop-2-enal

Case Based MCQs

Read the passage given below and answer the following questions.

When an aldehyde with no a-hydrogen reacts with concentrated aqueous NaOH, half the aldehyde is converted to carboxylic acid salt and other half is converted to an alcohol. In other words, half of the reactant is oxidized and other half is reduced. This reaction is known as Cannizzaro reaction.

Question. Trichloroacetaldehyde is subjected to Cannizzaro’s reaction by using NaOH. The mixture of the products contains sodium trichloroacetate ion and another compound. The other compounds is
(a) 2, 2, 2-trichloroethanol
(b) trichloromethanol
(c) 2, 2, 2-trichloropropanol
(d) chloroform.
Answer: a

Question. A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives
(a) benzyl alcohol and sodium formate
(b) sodium benzoate and methyl alcohol
(c) sodium benzoate and sodium formate
(d) benzyl alcohol and methyl alcohol.
Answer: a

Question. Which of the following reaction will not result in the formation of carbon-carbon bonds?
(a) Cannizzaro reaction
(b) Wurtz reaction
(c) Reimer-Tiemann reaction
(d) Friedel-Crafts’ acylation
Answer: a

Question. Which of the following compounds will undergo Cannizzaro reaction?
(a) CH₃CHO
(b) CH₃COCH₃
(c) C₆H₅CHO
(d) C₆H₅CH₂CHO
Answer: c

Assertion & Reasoning Based MCQs

For question , a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

Question. Assertion : Boiling point of aldehydes lie in between parent alkanes and corresponding alcohols.
Reason : Aldehydes cannot form intermolecular hydrogen bonds like alcohols.
Answer: b

Question. Assertion : Hydrogen bonding in carboxylic acids is stronger than alcohols.
Reason : Highly branched carboxylic acids are more acidic than unbranched acids.
Answer: c

Question. Assertion : Ketones can be converted into acids by haloform reaction.
Reason : Addition of Grignard reagents to dry ice followed by hydrolysis gives ketones.
Answer: c

Question. Assertion : o-Substituted benzoic acids are generally stronger acids than benzoic acids.
Reason : Increased strength is due to ortho-effect.
Answer: a

Question. Assertion : NaHSO3 is used for the purification of carbonyl compounds.
Reason : They are used in the blending of perfumes and flavouring agents.
Answer: b

Question. Assertion : Acetic acid in vapour state shows a molecular mass of 120.
Reason : It undergoes intermolecular hydrogen bonding.
Answer: a

Question. Assertion : Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.
Reason : Aromatic aldehydes are almost as reactive as formaldehyde.
Answer: c

Question. Assertion : Nitration of benzoic acid gives m-nitrobenzoic acid.
Reason : Carboxyl group increases the electron density at the meta-position.
Answer: c

Question. Assertion : Carboxylic acids are stabilised by resonance.
Reason : Chloroacetic acid is weaker than acetic acid.
Answer: c

Question. Assertion : Benzaldehyde undergoes aldol condensation.
Reason : Aldehydes having a-hydrogen atom undergo aldol condensation.
Answer: d

Question. Assertion : a-Hydrogen atoms in aldehydes and ketones are acidic.
Reason : The anion left after the removal of a-hydrogen is stabilised by inductive effect.
Answer: c

Question. Assertion : Carboxylic acids have higher boiling points than alkanes.
Reason : Carboxylic acids are resonance hybrids.
Answer: b

Question. Assertion : Formic acid is a stronger acid than benzoic acid.
Reason : pKa of formic acid is lower than that of benzoic acid.
Answer: b

Question. Assertion : m-Chlorobenzoic acid is a stronger acid than p-chlorobenzoic acid.
Reason : In m-chlorobenzoic acid both – I-effect and +R-effect of Cl operate but in p-chlorobenzoic acid only +R-effect of Cl operates.