Top 50 NEET Negative Marking Traps

Common Mistake: Thinking posterior pituitary synthesizes oxytocin and vasopressin.
Truth: The posterior pituitary (neurohypophysis) does not synthesize any hormones! Oxytocin and ADH are synthesized by hypothalamic nuclei (PVN & SON) and only stored & released by the posterior pituitary.

Common Mistake: Marking lignin or cutin as Casparian strip material.
Truth: Casparian strips are composed strictly of water-impermeable suberin, located on radial and tangential walls of root endodermal cells.

Common Mistake: Stating pyramid of biomass is always upright.
Truth: Pyramid of biomass in an aquatic (sea/lake) ecosystem is inverted because zooplankton biomass exceeds short-lived phytoplankton. ONLY the Pyramid of Energy is ALWAYS upright.

Common Mistake: Using $g' = g(1 - 2h/R)$ when $h = R$.
Truth: $g' = g(1 - 2h/R)$ is only valid when $h \ll R$ (e.g. few km). When $h = R$, the exact equation $g' = g \frac{R^2}{(R+h)^2} = g/4$ MUST be used.

Common Mistake: Writing $R' = 2R$ when a wire is stretched to double its length.
Truth: Stretching conserves volume: length doubles $\implies$ cross-sectional area halves $\implies R' = 4R$. Only if a second identical wire is added in series does resistance become $2R$.

Common Mistake: Assuming all aldehydes give Cannizzaro reaction.
Truth: Cannizzaro reaction occurs ONLY in aldehydes with no $\alpha$-hydrogen (e.g. Benzaldehyde, Formaldehyde). Aldehydes with $\alpha$-hydrogens undergo Aldol condensation.

Common Mistake: Assuming $\text{H}_3\text{PO}_4$ is the strongest reducing agent because it has more oxygens.
Truth: Reducing nature is governed by the number of direct $\text{P}-\text{H}$ bonds. $\text{H}_3\text{PO}_2$ has TWO $\text{P}-\text{H}$ bonds and is the strongest reducing agent among phosphorus oxoacids.