AQA A-Level Chemistry 7405
Atomic Structure
Amount of Substance
Bonding
Energetics and Thermodynamics
Kinetics
Chemical Equilibria
Redox and Electrochemistry
Acids and Bases
Periodicity and Group Chemistry
Period 3 Elements and Their Oxides
Transition Metals
Introduction to Organic Chemistry
Hydrocarbons
Halogenoalkanes, Alcohols and Organic Analysis
Carbonyls, Carboxylic Acids and Derivatives
Aromatic Chemistry and Amines
Polymers, Amino Acids, Proteins and DNA
Organic Synthesis, NMR and Chromatography
Carbonyls, Carboxylic Acids and Derivatives
Oxidation of Aldehydes and Distinguishing Tests
- 3 things to know
- Papers 2 and 3
Overview
Why aldehydes oxidise and ketones do not, and the tests that show it.
What you need to know
Answer each one before you reveal it.
What is the positive result when Fehling's solution reacts with an aldehyde?
What is the positive result when Tollens' reagent reacts with an aldehyde?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What type of oxidation product do aldehydes readily form?
Model answer
Carboxylic acids
- 2
What reagent can be used to distinguish between aldehydes and ketones based on the formation of a brick-red precipitate?
Model answer
Fehling's solution
- 3
What reagent can be used to distinguish between aldehydes and ketones based on the formation of a silver mirror?
Model answer
Tollens' reagent
- 4
What is the positive result when Fehling's solution reacts with an aldehyde?
Model answer
A brick-red precipitate forms
- 5
What is the positive result when Tollens' reagent reacts with an aldehyde?
Model answer
A silver mirror forms on the inside of the test tube
- 6
Why do aldehydes give a positive result with Fehling's solution and Tollens' reagent while ketones do not?
Model answer
Aldehydes can be readily oxidised to carboxylic acids, whereas ketones cannot be easily oxidised
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