Aldehydes Ketones and Carboxylic Acids JEE Main PYQs (2020–2026)

Solved Aldehydes Ketones and Carboxylic Acids PYQs

3 recent questions with answers. The full set of 214 is free to practise.

1. JEE Main 2026MediumReactions Involving Alpha-Hydrogen and Cannizzaro Reaction
   Q1

   Given below are two statements :
   
   Statement I : Cross aldol condensation between two different aldehydes will always produce four different products.
   
   Statement II : When semicarbazide reacts with a mixture of benzaldehyde and acetophenone under optimum pH , it forms a condensation product with acetophenone only.
   
   In the light of the above statements, choose the correct answer from the options given below

   • AStatement I is true but Statement II is false
   • BBoth Statement I and Statement II are false
   • CBoth Statement I and Statement II are true
   • DStatement I is false but Statement II is true

   Show answer & solution

   Correct answer: (B)

   Statement I: False.
   
   A crossed aldol between two different aldehydes gives four products only in the uncontrolled case when both aldehydes have α‑H (2 self‑aldols + 2 crossed). It is not “always”: e.g., benzaldehyde (no α‑H) cannot self‑aldol, so fewer products result; and under controlled conditions you can also avoid mixtures.
   
   Statement II: False.
   
   Semicarbazide forms semicarbazones with both aldehydes and ketones, and aldehydes (benzaldehyde) generally react faster than ketones (acetophenone) under the usual “optimum pH” conditions. So it will not give a condensation product with acetophenone only.
   
   Correct option: B — Both Statement I and Statement II are false.
2. JEE Main 2026EasyCarboxylic Acids: Preparation, Physical Properties and Acidity
   Q2

   Grignard reagent $RMgBr(P)$ reacts with water and forms a gas $(Q)$ . One gram of Q occupies $1.4{dm}^3$ at STP. (P) on reaction with dry ice in dry ether followed by $H_3{O}^{+}$ forms a compound (Z). 0.1 mole of (Z) will weigh $\_\_\_\_$ g. (Nearest integer)

   Numerical answer type

   Show answer & solution

   Correct answer: 6

   With water, a Grignard reagent gives the corresponding hydrocarbon:
   
   $$RMgBr+H_{2}O\to RH(Q)+Mg(OH)Br$$
   
   Given 1 g of $Q$ occupies $1.4{\text{dm}}^3$ at STP.
   
   Moles in $1.4{\text{dm}}^3$ :
   
   $$n=\frac{1.4}{22.4}=0.0625\text{mol}$$
   
   So molar mass of $Q$ :
   
   $$M=\frac{1}{0.0625}=16{\text{g mol}}^{-1}$$
   
   A hydrocarbon gas with molar mass 16 is methane, $C{H}_4$ . Hence $R=C{H}_3$ , and $P=C{H}_{3}MgBr$ .
   
   Carboxylation with dry ice followed by acid workup gives:
   
   $$C{H}_{3}MgBr\underset{ether}{\stackrel{C{O}_2}{\to }}C{H}_{3}CO{O}^{-}MgBr\stackrel{H_3{O}^{+}}{\to }C{H}_{3}COOH(Z)$$
   
   So $Z$ is acetic acid, $C{H}_{3}COOH$ , with molar mass $60{\text{g mol}}^{-1}$ .
   
   Mass of $0.1$ mol:
   
   $$0.1\times 60=6\text{g}$$
   
   Answer: 6 g
3. JEE Main 2025EasyOxidation, Reduction and Characteristic Tests of Aldehydes and Ketones
   Q3

   Both acetaldehyde and acetone (individually) undergo which of the following reactions?
   
   A. Iodoform Reaction
   
   B. Cannizaro Reaction
   
   C. Aldol Condensation
   
   D. Tollen’s Test
   
   E. Clemmensen Reduction
   
   Choose the correct answer from the options given below:

   • AC and E Only
   • BA, B and D Only
   • CA, C and E Only
   • DB, C and D Only

   Show answer & solution

   Correct answer: (C)

   S.No.
   
   Name of Reaction
   
   Acetaldehyde
   
   Image
   
   Acetone
   
   Image
   
   1
   
   Iodoform reaction
   
   $\oplus$ ve
   
   $\oplus$ ve
   
   2
   
   Cannizaro
   
   $\ominus$ ve
   
   $\ominus$ ve
   
   3
   
   Aldol reaction
   
   $\oplus$ ve
   
   $\oplus$ ve
   
   4
   
   Tollen’s test
   
   $\oplus$ ve
   
   $\ominus$ ve
   
   5
   
   Clemmensen reduction
   
   $\oplus$ ve
   
   $\oplus$ ve
   
   Ans. (2) A, C and E only.

Topic-wise question count

Where JEE Main has asked from Aldehydes Ketones and Carboxylic Acids, most frequent first.

• Oxidation, Reduction and Characteristic Tests of Aldehydes and Ketones49
• Nucleophilic Addition Reactions of Aldehydes and Ketones46
• Nomenclature, Structure and Preparation of Aldehydes and Ketones33
• Reactions Involving Alpha-Hydrogen and Cannizzaro Reaction30
• Chemical Reactions of Carboxylic Acids and Derivatives28
• Carboxylic Acids: Preparation, Physical Properties and Acidity28

Year-wise Aldehydes Ketones and Carboxylic Acids questions in JEE Main

Number of questions from this chapter in each year's paper(s).