Fehling solution A and Fehling solution B are:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Aqueous CuSO4 solution and alkaline solution of sodium potassium tartrate.
In Fehling’s reagent the tartrate of solution B holds the \( \ce{Cu^2+} \) ions of solution A in solution as a complex, so that copper(II) hydroxide does not precipitate in the alkaline medium.
On heating an aldehyde with the reagent, the aldehyde is oxidised to the carboxylate ion and \( \ce{Cu^2+} \) is reduced to a reddish brown precipitate of \( \ce{Cu2O} \):
\( \displaystyle \ce{R-CHO + 2Cu^2+ + 5OH^- -> RCOO^- + Cu2O v + 3H2O} \)
NCERT (2026-27 edition):
Fehling’s Test
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | 02-06 S1 | – | 27-05 S1 | – |