Free Aldehydes and Ketones MCQs with Answers
22 Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
22 questions · page 3 of 3
21. Acetaldehyde undergoes oxidation to produce acetic acid. In this reaction the oxidizing agent used is:
- A. HI
- B. LiAlH4
- C. K2Cr2O7
- D. NaBH4
Explanation: Acidified potassium dichromate is the standard oxidising agent for converting an aldehyde to a carboxylic acid, turning from orange to green as chromium is reduced from plus 6 to plus 3. Lithium aluminium hydride and sodium borohydride are reducing agents and would drive the reaction the other way, back towards the alcohol. Hydrogen iodide is a reducing agent as well.
Correct answer: K2Cr2O722. Methanol is produced by reduction of
- A. Formaldehyde
- B. Acetaldehyde
- C. Propanal
- D. Propanone
Explanation: Reducing an aldehyde adds hydrogen across the carbonyl group and gives a primary alcohol with the same number of carbon atoms, so the one carbon aldehyde formaldehyde gives the one carbon alcohol methanol. Acetaldehyde would give ethanol and propanal would give propan-1-ol. Propanone is a ketone and would give a secondary alcohol, propan-2-ol.
Correct answer: Formaldehyde