Reaction Summary
Reagents
- Tollens’ reagent: Tollens’ reagent — ammoniacal silver nitrate,
(alkaline) - Fehling’s solution: Fehling’s solution —
complexed in alkaline solution
Conditions
- Tollens’ reagent: Warm gently in a water bath (no naked flame)
- Fehling’s solution: Warm gently in a water bath
Catalyst
- None
Chemical Equation
Tollens’ reagent
Equation
By-Products
(silver metal)
Fehling’s solution
Equation
By-Products
(copper(I) oxide)
Observations
Observations
- Tollens’ reagent: Colourless solution ➔ silver mirror forms on the inside of the tube (or grey/black ppt)
- Fehling’s solution: Blue solution ➔ brick-red precipitate of
⚠️ 9701 Exam Notes / Pitfalls
Warning
- Both reagents are alkaline, so the product is the carboxylate ion
, not . Acidify separately (dilute / ) to obtain the acid. - Ketones give no reaction with either — this is the standard aldehyde vs ketone distinguishing test.
- Oxidising agent:
is reduced to (Tollens); is reduced to in (Fehling’s). - Simplified form accepted:
.