Chapter-8 Aldehydes — Online MCQ Test
CHEMISTRY · CLASS 12 INTER II YEAR · Andhra State Board
Practice Chapter-8 Aldehydes with a free chapter-wise online MCQ test.
This chapter covers: Ketones and Carboxylic Acids preparation - properties - acidity - basicity - reaction mechanisms.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-8 Aldehydes — Important Questions & Answers
What is the general structure of an aldehyde?
- A. R-CO-R'
- B. R-CHO
- C. R-COOH
- D. R-OH
Answer: B. R-CHO
Aldehydes contain a carbonyl group (C=O) bonded to at least one hydrogen atom, represented as R-CHO where R is an alkyl or aryl group.
Aldehydes contain a carbonyl group (C=O) bonded to at least one hydrogen atom, represented as R-CHO where R is an alkyl or aryl group.
Which compound is a ketone?
- A. Propanal
- B. Propanone
- C. Propanoic acid
- D. Propanol
Answer: B. Propanone
Propanone (CH₃-CO-CH₃) is a ketone with the carbonyl group between two carbon atoms, whereas propanal is an aldehyde.
Propanone (CH₃-CO-CH₃) is a ketone with the carbonyl group between two carbon atoms, whereas propanal is an aldehyde.
Which carbonyl compound is most polar?
- A. Benzaldehyde
- B. Formaldehyde
- C. Acetone
- D. Hexanal
Answer: B. Formaldehyde
Formaldehyde (HCHO) is the smallest aldehyde with the highest electronegativity difference between C=O and the least steric hindrance, making it most polar.
Formaldehyde (HCHO) is the smallest aldehyde with the highest electronegativity difference between C=O and the least steric hindrance, making it most polar.
Scenario: A compound shows positive Tollens' test and positive iodoform test. What can be concluded?
- A. It is a methyl ketone
- B. It is acetaldehyde
- C. It contains both aldehyde and methyl ketone groups
- D. It is formaldehyde
Answer: B. It is acetaldehyde
Acetaldehyde (CH₃CHO) gives a positive Tollens' test (it's an aldehyde) and a positive iodoform test (has CH₃- group adjacent to carbonyl), making it the compound that satisfies both criteria.
Acetaldehyde (CH₃CHO) gives a positive Tollens' test (it's an aldehyde) and a positive iodoform test (has CH₃- group adjacent to carbonyl), making it the compound that satisfies both criteria.
What happens when a mixture of acetaldehyde and formaldehyde is treated with dilute NaOH?
- A. Only formaldehyde undergoes Cannizzaro reaction
- B. Both undergo aldol condensation
- C. Only acetaldehyde undergoes aldol condensation
- D. Formaldehyde undergoes Cannizzaro reaction while acetaldehyde undergoes aldol condensation
Answer: D. Formaldehyde undergoes Cannizzaro reaction while acetaldehyde undergoes aldol condensation
Formaldehyde (having no α-hydrogen) undergoes the Cannizzaro reaction producing methanol and formic acid, while acetaldehyde (with α-hydrogen) undergoes aldol condensation with itself or formaldehyde.
Formaldehyde (having no α-hydrogen) undergoes the Cannizzaro reaction producing methanol and formic acid, while acetaldehyde (with α-hydrogen) undergoes aldol condensation with itself or formaldehyde.