Aldehydes and Ketones Practice Questions PDF

1. Which functional group do aldehydes and ketones both contain? * A) Hydroxyl * B) Carbonyl * C) Carboxyl * D) Amino 2. What is the general formula for an aldehyde? * A) RCHO * B) RCOR * C) RCOOH * D) RCH2OH 3. What is the general formula for a ketone? * A) RCHO * B) RCOR' * C) RCOOH * D) RCH2OH...

1. Which functional group do aldehydes and ketones both contain? * A) Hydroxyl * B) Carbonyl * C) Carboxyl * D) Amino 2. What is the general formula for an aldehyde? * A) RCHO * B) RCOR * C) RCOOH * D) RCH2OH 3. What is the general formula for a ketone? * A) RCHO * B) RCOR' * C) RCOOH * D) RCH2OH 4. Which of the following reagents can be used to distinguish between an aldehyde and a ketone? * A) 2,4-Dinitrophenylhydrazine (2,4-DNPH) * B) Tollen's reagent * C) Acidi ed potassium dichromate(VI) * D) Both Tollen's reagent and Fehling's solution 5. What is the positive result for Tollen's reagent with an aldehyde? * A) A yellow precipitate forms * B) A silver mirror forms * C) A red precipitate forms * D) The solution turns from orange to green 6. What is the positive result for Fehling’s solution with an aldehyde? * A) A yellow precipitate forms * B) A silver mirror forms * C) A red precipitate forms * D) The solution turns from orange to green 7. What is the organic product formed when an aldehyde is oxidised? * A) A ketone * B) A carboxylic acid fi * C) An alcohol * D) An alkane 8. What is the organic product when a ketone is reacted with 2,4- DNPH? * A) No reaction * B) A yellow/orange precipitate * C) A carboxylic acid * D) An alcohol. 9. How is the identity of an unknown carbonyl compound determined after reacting with 2,4-DNPH? * A) The melting point of the precipitate is measured and compared to a data book. * B) The precipitate is dissolved in water. * C) The precipitate is burned and the products tested. * D) There is no need to isolate the precipitate. 10. Which of the following reagents is used in the nucleophilic addition reaction with aldehydes and ketones to form hydroxynitriles? * A) NaBH4 * B) KCN followed by dilute acid * C) LiAlH4 * D) Concentrated H2SO4 11. What is the nucleophile in the reaction of an aldehyde with KCN followed by dilute acid? * A) CN- * B) K+ * C) HCN * D) H+ 12. What is the name of the mechanism for the reaction of aldehydes and ketones with KCN followed by dilute acid? * A) Electrophilic Addition * B) Electrophilic Substitution * C) Nucleophilic Addition * D) Nucleophilic Substitution. 13. What type of product is formed when an aldehyde reacts with KCN followed by dilute H2SO4? * A) A carboxylic acid * B) A hydroxynitrile * C) An amine * D) An ester 14. What is the name given to the product formed when propanal reacts with HCN? * A) 2-hydroxybutanenitrile * B) 2-hydroxypropanenitrile * C) 1-hydroxybutanenitrile * D) 1-hydroxypropanenitrile 15. Why is KCN used instead of HCN in the reaction with carbonyls, despite HCN being the reactant? * A) KCN is more reactive. * B) HCN is a toxic gas. * C) KCN is a catalyst. * D) KCN is cheaper 16. What is the shape around the C=O bond in an aldehyde? * A) Tetrahedral * B) Trigonal planar * C) Linear * D) Pyramidal 17. If an aldehyde, other than methanal, is reacted with HCN, what can be said about the organic product? * A) It will form a racemic mixture of optical isomers. * B) It will be a single optical isomer. * C) It will not display optical isomerism * D) It will form structural isomers. 18. Why does the nucleophilic addition of HCN to an aldehyde (except methanal) produce a racemic mixture? * A) The aldehyde is planar around the C=O bond, so attack can occur from either side. * B) The cyanide ion is a strong nucleophile. * C) The reaction is carried out in acidic conditions. * D) The reaction is reversible. 19. The iodoform test is positive for which of the following groups? * A) CH3CH(OH)- * B) CH3CO- * C) -COOH * D) -CH2OH 20. What is observed in a positive iodoform test? * A) A yellow precipitate * B) A silver mirror * C) A red precipitate * D) Misty Fumes Answers and Explanations: 1. B - Carbonyl (C=O) 2. A - RCHO (The carbonyl is at the *end* of the chain) 3. B - RCOR' (The carbonyl is *within* the chain) 4. D - Tollen's and Fehling's both distinguish by oxidising aldehydes, but not ketones. 5. B - Silver mirror (Ag+ is reduced to Ag) 6. C 7. B - Aldehydes are oxidised to carboxylic acids. 8. B - All carbonyls form a yellow/orange precipitate with 2,4-DNPH. 9. A 10. B - KCN provides CN-, and dilute acid provides H+ for the mechanism. 11. A 12. C 13. B - A hydroxynitrile (containing -OH and -CN groups) 14. A 15. B - HCN is a highly toxic gas, KCN is safer (though still toxic). 16. B 17. A 18. A - Because it is planar, the CN- can attack from above or below with equal probability. 19. B 20. A - Triiodomethane (CHI3) is a pale yellow precipitate.