The red-brown precipitate produced during Fehling's test, is

The correct answer is Option (3) → Cu₂O

Fehling’s reagent is made just before use by mixing Fehling solution A (aqueous copper sulphate) and Fehling solution B (alkaline sodium potassium tartrate). The tartrate keeps the \( \ce{Cu^{2+}} \) ions in solution as a deep blue complex.

On warming with an aldehyde, the aldehyde is oxidised to a carboxylate ion and Cu²⁺ is reduced to Cu⁺, which separates as a red-brown precipitate of copper(I) oxide:

    \( \displaystyle \ce{R-CHO + 2Cu^2+ + 5OH^- -> R-COO^- + Cu2O v + 3H2O} \)

So the red-brown precipitate is Cu₂O.

NCERT (2026-27 edition):
Fehling’s Test