Error 1 — N+S gives Prussian blue: This is the number one NEET trap. When both N and S are present, NaSCN forms, and FeCl3 gives BLOOD-RED, not Prussian blue. Prussian blue is only for N alone. Blood-red is for N+S together.

Error 2 — Fehling's test for benzaldehyde: Students assume ALL aldehydes give positive Fehling's test. Wrong. Aromatic aldehydes (benzaldehyde, C6H5CHO) give NEGATIVE Fehling's test. Only aliphatic aldehydes are strong enough reducing agents.

Error 3 — Indicator in KMnO4 titration: Students add phenolphthalein, methyl orange, or starch to KMnO4 titrations. None are needed. KMnO4 is its own indicator. Adding anything external is incorrect.

Error 4 — Iodoform for any ketone: Students mark all ketones as positive for iodoform test. Only METHYL ketones (CH3CO-) give CHI3. 3-Pentanone (C2H5COC2H5) gives NEGATIVE iodoform test.

Error 5 — AgNO3 test without HNO3 pretreatment: When N or S is present, skipping the HNO3 boiling step before AgNO3 causes interference from AgCN (white, mimics AgCl) and Ag2S (black). The result will be misleading.

Error 6 — Carbylamine for secondary amines: Carbylamine test $\frac{foul isocyanide smell with CHCl3}{KOH}$ is exclusively for PRIMARY amines. Secondary amines give NO foul smell.

Error 7 — Phenol + NaHCO3 gives CO2: Phenol is a weak acid but DOES NOT react with NaHCO3 to give CO2 effervescence. Only carboxylic acids (-COOH) give CO2 with NaHCO3. This distinguishes phenol from carboxylic acid.