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CAIE A-Level Chemistry AS 17.1.5 The Nature Aldehyde or Ketone of an Unknown Questions

Practise distinguishing aldehydes from ketones in CAIE 9701 using Tollens’ and Fehling’s observations, oxidation behaviour and reduction products.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • identify an aldehyde from a silver mirror with Tollens’ reagent or brick-red precipitate with Fehling’s
  • identify a ketone when 2,4-DNPH is positive but Tollens’ and Fehling’s tests remain negative
  • use reduction product and oxidation behaviour as supporting evidence when several functional groups are possible

CAIE A-Level Chemistry AS 17.1.5 The Nature Aldehyde or Ketone of an Unknown Questions question 1

[Maximum number: 1]

Compound Y:

- changes the colour of acidified K2Cr2O7\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} from orange to green

- has no effect on Fehling's reagent

- produces an orange precipitate with 2,4-dinitrophenylhydrazine reagent.

What is compound Y ?

A
Figure for Question CAIE A-Level Chemistry AS 17.1.5 The Nature Aldehyde or Ketone of an Unknown Questions question 1 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question CAIE A-Level Chemistry AS 17.1.5 The Nature Aldehyde or Ketone of an Unknown Questions question 1 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question CAIE A-Level Chemistry AS 17.1.5 The Nature Aldehyde or Ketone of an Unknown Questions question 1 — CAIE A-Level Chemistry AS — Option C

HOCH2CH2CH2CH2OH\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}

D

Option D as shown in the official source

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