Reactions of aldehydes and ketones Quiz
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5 questions, one answer each
Each answer is checked as you go, with why.
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1. Which observation shows that a liquid is an aldehyde rather than a ketone?
- A. It turns Fehling's solution from blue to a red precipitate
- B. It turns acidified dichromate(VI) from orange to green only with a ketone
- C. It gives no change with Tollens' reagent
- D. It turns bromine water colourless
2. Butanone is reduced with NaBH₄. What is the product?
- A. Butanal
- B. Butan-1-ol
- C. Butanoic acid
- D. Butan-2-ol
3. In the mechanism for reduction by NaBH₄, which species attacks the carbonyl carbon?
- A. H⁺
- B. OH⁻
- C. H⁻
- D. Na⁺
4. Which equation correctly shows the reduction of propanal using [H]?
- A. CH₃CH₂CHO + [H] → CH₃CH₂CH₂OH
- B. CH₃CH₂CHO + 2[H] → CH₃CH₂CH₂OH
- C. CH₃CH₂CHO + 2[H] → CH₃CH₂COOH
- D. CH₃CH₂CHO + 2[H] → CH₃CH(OH)CH₃
5. Why does a ketone give no silver mirror with Tollens' reagent?
- A. It is more reactive than an aldehyde
- B. It is not easily oxidised, so Ag⁺ is not reduced
- C. It reduces Ag⁺ to silver too slowly to see
- D. It forms a carboxylic acid that blocks the reaction