Aldehydes & Ketones MCQs set 2 for COMSATS Entry Test Chemistry — 20 solved questions.
Q1. The reaction of aldehydes with Tollens' reagent results in the formation of?
Answer: Silver mirror
Explanation: Tollens' reagent oxidizes aldehydes to carboxylates, reducing Ag+ to Ag, forming a silver mirror on the inner surface of the reaction vessel.
Q2. The general formula for aldehydes and ketones is?
Answer: CnH2nO
Explanation: The general formula CnH2nO represents the common structure of aldehydes and ketones, where n is the number of carbon atoms.
Q3. Which of the following is a characteristic reaction of aldehydes?
Answer: Nucleophilic addition
Explanation: Aldehydes undergo nucleophilic addition due to the partial positive charge on the carbonyl carbon, making it susceptible to nucleophilic attack.
Q4. The compound that does not react with NaHSO3 is?
Answer: Benzaldehyde
Explanation: Benzaldehyde does not react with NaHSO3 due to steric hindrance and lack of alpha hydrogen, but primarily because it's an aromatic aldehyde.
Q5. The strongest reducing agent among the following is?
Answer: Formaldehyde
Explanation: Formaldehyde is the strongest reducing agent due to its ability to easily donate electrons and get oxidized.
Q6. The reaction of ketones with NaHSO3 results in?
Answer: Addition product
Explanation: Ketones react with NaHSO3 to form an addition product, which is a bisulfite addition compound.
Q7. The functional group in aldehydes and ketones is?
Answer: Both A and B
Explanation: Both aldehydes (-CHO) and ketones (-CO-) contain a carbonyl group, which is the characteristic functional group.
Q8. The reaction of aldehydes with Fehling's solution results in?
Answer: Precipitate of Cu2O
Explanation: Aldehydes reduce Fehling's solution (Cu2+), resulting in the formation of a red precipitate of Cu2O.
Q9. The compound that is used as a starting material for the synthesis of many organic compounds is?
Answer: Formaldehyde
Explanation: Formaldehyde is a versatile starting material due to its high reactivity and ability to undergo various reactions.
Q10. The reagent used to distinguish between aldehydes and ketones is?
Answer: Both A and B
Explanation: Both Tollens' reagent and Fehling's solution can distinguish between aldehydes and ketones, as aldehydes react with both, while ketones do not.
Q11. The reaction of acetone with HCN results in?
Answer: Addition product
Explanation: Acetone reacts with HCN to form an addition product, which is a cyanohydrin.
Q12. The compound that is used in the manufacture of resins is?
Answer: Formaldehyde
Explanation: Formaldehyde is used in the production of various resins, such as phenol-formaldehyde resins.
Q13. The strongest oxidizing agent among the following is?
Answer: KMnO4
Explanation: KMnO4 is a strong oxidizing agent used to oxidize various organic compounds.
Q14. The reaction of benzaldehyde with NH3 results in?
Answer: Imine
Explanation: Benzaldehyde reacts with NH3 to form an imine, also known as a Schiff base.
Q15. The compound that gives a positive Benedict's test is?
Answer: Acetaldehyde
Explanation: Aldehydes, such as acetaldehyde, reduce Benedict's solution, giving a positive test.
Q16. The functional group isomerism is exhibited by?
Answer: Aldehydes and ketones
Explanation: Aldehydes and ketones exhibit functional group isomerism, as they have the same molecular formula but different functional groups.
Q17. The reaction of aldehydes with 2,4-DNP results in?
Answer: Precipitate
Explanation: Aldehydes react with 2,4-DNP to form a hydrazone, which is a yellow or orange precipitate.
Q18. The compound that is used as a solvent is?
Answer: Acetone
Explanation: Acetone is commonly used as a solvent due to its high solvency and low boiling point.
Q19. What is the general formula for aldehydes?
Answer: CnH2n+1CHO
Explanation: The general formula for aldehydes is CnH2n+1CHO, where n is the number of carbon atoms in the alkyl group.
Q20. Which of the following aldehydes is used as a disinfectant?
Answer: Formaldehyde
Explanation: Formaldehyde is used as a disinfectant due to its ability to denature proteins and kill bacteria.