Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

Incorrect statement among the following is:

FeCl₃ is used in the detection of phenol.

Fehling solution is used in the detection of glucose.

Tollen reagent is used in the detection of unsaturation.

NaHSO₃ is used in the detection of carbonyl compounds.

FeCl₃ Test: Neutral Ferric Chloride ( $FeCl_3$ ) is indeed used to detect phenols. It reacts with phenols to give a violet-coloured complex.
Fehling's Solution: This is a standard test for reducing sugars like glucose. It oxidizes glucose, and in the process, the copper(II) ions are reduced to a red precipitate of copper(I) oxide ( $Cu_2O$ ).
Tollen's Reagent: Tollen's reagent (Ammoniacal Silver Nitrate) is used to detect aldehydes (which reduce it to metallic silver, forming a 'silver mirror'), not unsaturation. Unsaturation (double/triple bonds) is detected using Bromine water (which gets decolourised) or Baeyer's reagent (alkaline $KMnO_4$ , which gets decolourised) .
NaHSO₃ Test: Sodium hydrogen sulphite ( $NaHSO_3$ ) forms crystalline addition products with aldehydes and ketones (carbonyl compounds), which is used for their separation and purification.

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