All Free Chemistry MCQs with Answers

• A. Formaldehyde cyanohydrin
• B. Acetaldehyde cyanohydrin
• C. Acetone cyanohydrin
• D. Butanone cyanohydrin

Explanation: When HCN is added to a carbonyl compound like acetaldehyde, a nucleophilic addition reaction occurs, resulting in the formation of a…

• A. Acetophenone
• B. Benzaldehyde
• C. 3-Butanone
• D. 3-pentyl 2-pentanone

Explanation: 3-Methyl-2-pentartone gives 3-Methyl-2-pentanol on reduction with NaBH4'

• A. Methanol
• B. Ethanal
• C. Propanone
• D. 2-pentanone

Explanation: Aldol condensation is a reaction shown by aldehydes and ketones containing at least one α-hydrogen atom in the presence of dilute base.

• A. They have lower boiling points than that of alkalies.
• B. They have higher boiling points than that of alcohols.
• C. They have a lower boiling point than resulting camphor.
• D. Aldehydes have H-bonding but ketones do not have.

Explanation: Explanation:The correct option is B, they have higher boiling points than that of alcohols.Alcohols have strong intermolecular hydrogen…

• A. Sodium nitroprusside test
• B. Tollen's reagent test
• C. Fehling's solution test
• D. Benedict's reagent test

Explanation: Option A is correct.Sodium nitroprusside test is shown by ketones only.

• A. Aldehydes on reduction with NaBH4/H3O+ give 1o alcohol
• B. Ketones on reduction with NaBH4/H3O+ give 2o alcohol
• C. Aldehydes on reduction with N2H4/KOH gives alkane
• D. none

Explanation: The correct answer is 'none' because all of the given statements about the reduction of aldehydes and ketones are accurate.

• A. An aldehyde can be represented by general formula (R-C-H)
• B. A ketone can be represented by general formula (R-CO-R' )
• C. Ketone group is present in camphor and menthone
• D. The homologous series of both aldehydes and ketones have general formula CH2nO

Explanation: Amongst the four given options , the incorrect one is A. An aldehyde is generally represented by RCHO .

• A. Having no a-hydrogen
• B. Having a-hydrogen
• C. Having a methyl group
• D. Difficult to predict

Explanation: Option A is correct.A carbonyl compound must have at least one alpha-hydrogen to undergo aldol condensation.

• A. Primary alcohols
• B. Secondary alcohols
• C. Tertiary alcohols
• D. Carboxylic acids

Explanation: Option A is correct. Primary alcohols (R-CH₂OH) are the only class that can be oxidized to aldehydes in the presence of acid dichromate (…

• A. methanal
• B. ethanal
• C. propanal
• D. hexanone

Explanation: The compound with the highest boiling point is (d) hexanone.Here's a breakdown of the factors influencing boiling points and why the other…

• A. reaction with HCN
• B. reaction with NaHSO4
• C. reaction with 2,4 dinitrophenyl hydrazine
• D. reaction with Fehling

Explanation: While ketones are versatile reagents involved in numerous reactions, they refuse to play nice with Fehling's solution.

• A. sp hybridized
• B. sp2 hybridized
• C. sp3 hybridized
• D. dsp2 hybridized

Explanation: The carbon atom in the carbonyl group forms three sigma bonds: one with the oxygen atom to make the double bond and two with other atoms…

• A. electrophillic addition
• B. electrophilic substitution
• C. nucleophilic addition
• D. nucleophilic substitution

Explanation: In this reaction, the cyanide ion (CN-) acts as a nucleophile. This means it is electron-rich and seeks to attack an electron-deficient…

• A. formaldehyde
• B. acetaldehyde
• C. benzaldehyde
• D. trimethly acetaldehyde

Explanation: Cannizzaro's reaction requires aldehydes without an α-hydrogen, the hydrogen atom directly attached to the carbon next to the carbonyl…

• A. alkly groups are electron donating
• B. steric hindrance
• C. both (a) & (b)
• D. none

Explanation: The key lies in the crowd around the carbonyl carbon. Aldehydes have only one "guest" - an alkyl group attached to the carbon next to the…

• A. PdCl2
• B. PbCl2
• C. CuCl2
• D. None of the above

Explanation: The Wacker process is the industrial method for producing ethanal from ethylene.

• A. НСНО
• B. C6H5CHO
• C. Сl3CCHO
• D. CH3COCH3

Explanation: Aldol condensation involves the reaction of an aldehyde or ketone with its enol or enolate form to form a β-hydroxyaldehyde or…

• A. apha-C
• B. Alpha -H
• C. Basic medium
• D. All

Explanation: While each individual option plays a vital role, a successful aldol condensation requires a well-orchestrated combination of the following…

• A. proton
• B. H+
• C. both a & b
• D. H-

Explanation: The tetrahydroborate ion (BH₄⁻) acts as a strong nucleophilic hydride donor, readily releasing its negatively charged hydrogen atom (H⁻)…

• A. The use of sintered glass crucible is most convenient way of filtration
• B. I2, C10H5, C6H5COOH undergo sublimation
• C. In solvent extraction, organic solvent is shaken with aqueous solution to increase area of contact
• D. Rf value always has a certain unit

Explanation: This statement is incorrect because not all substances listed undergo sublimation.