Tollens and Fehling (aldehyde Tests) — Fehling
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali).
Learning objectives
- Define fehling using accurate chemistry terms.
- Explain why fehling matters within tollens and fehling (aldehyde tests).
- Apply the learning unit to an FBISE-style example, comparison, diagram, or calculation.
Definition
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. This page separates the idea from the wider topic “TOLLENS AND FEHLING (ALDEHYDE TESTS)” so it can be revised and assessed on its own.
Important terms
- FEHLING
- Blue to brick red.
- TOLLENS AND FEHLING (ALDEHYDE TESTS)
- Tollens: ammoniacal silver, aldehydes give a silver mirror (Ag+ reduced).
Overview
Study this learning unit in three steps:
Key Idea
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test.
Examples Brick red · Ketone no · Heat
Exam Application
Exam Tollens: aldehyde: silver mirror ketone: no mirror aldehyde is oxidised; Ag+ is reduced
Examples Brick red · Ketone no · Heat
WHAT — TOLLENS AND FEHLING (ALDEHYDE TESTS) — FEHLING
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. This page separates the idea from the wider topic “TOLLENS AND FEHLING (ALDEHYDE TESTS)” so it can be revised and assessed on its own.
WHY — Why this topic matters
TOLLENS AND FEHLING (ALDEHYDE TESTS) — FEHLING is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW — How it works
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. Examples: Brick red; Ketone no; Heat. Exam use: Exam Tollens: aldehyde: silver mirror ketone: no mirror aldehyde is oxidised; Ag+ is reduced
Explanation
Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. Examples: Brick red; Ketone no; Heat. Exam use: Exam Tollens: aldehyde: silver mirror ketone: no mirror aldehyde is oxidised; Ag+ is reduced
In simple words
Federal Board Class 11 Chemistry learning unit. Easy wording; no provincial-board material added.
Key points
- Cu2+ -> Cu2O
- mirror = aldehyde
Exam preparation
Exam Focus
Quick revision
Revision Zone
Tollens and Fehling (aldehyde Tests) — Fehling
Sticky Notes · Quick Revision
Core idea
- Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. This page separates the idea from the wider topic “TOLLENS AND FEHLING (ALDEHYDE TESTS)” so it can be revised and assessed on its own.
WHAT
- Blue to brick red.
WHY
- TOLLENS AND FEHLING (ALDEHYDE TESTS) — FEHLING is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW
- Blue to brick red. Same tell: aldehyde oxidised to acid (carboxylate in alkali). Heat required. Combine with iodoform to pin a structure. Oxidation of aldehyde to carboxylate drives test. Examples: Brick red; Ketone no; Heat. Exam use: Exam Tollens: aldehyde: silver mirror ketone: no mirror aldehyde is oxidised; Ag+ is reduced
Common misconception
- Do not treat fehling as the same as every other part of tollens and fehling (aldehyde tests); define this unit and use its own evidence, steps, or conditions.
FBISE exam check
- Define tollens and fehling (aldehyde tests) — fehling, explain how it works, and support the answer with one relevant example.
60-second revision
- Blue to brick red.
- Brick red
- Exam link: Cu2+ -> Cu2O.
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