8 Common Error Traps and Corrections

Trap 1: HDPE/LDPE condition reversal (most common NEET trap)

• WRONG: "HDPE uses high pressure; LDPE uses low pressure."
• CORRECT: HDPE = Ziegler-Natta catalyst + LOW pressure → LINEAR chains. LDPE = free radical + HIGH pressure (1000–2000 atm) → BRANCHED chains.
• Memory: H in HDPE = Handled by ZN catalyst (not high pressure).

Trap 2: Normal rain pH = 7 (second most common trap)

• WRONG: "Normal rain is neutral (pH 7); acid rain is pH below 7."
• CORRECT: Normal rain pH = 5.6 (CO2 dissolves → H2CO3). Acid rain = pH BELOW 5.6.
• Memory: 5.6 = CO2 rain; below 5.6 = acid rain $\frac{SO2}{NOx}$.

Trap 3: Nylon-6 vs Nylon-6,6 monomer count

• WRONG: "Nylon-6,6 has one monomer with 6 carbons; Nylon-6 has two monomers each with 6 carbons."
• CORRECT: Nylon-6,6 = TWO monomers (hexamethylenediamine + adipic acid, 6C each). Nylon-6 = ONE monomer (caprolactam, ring-opening).
• Memory: "6,6" = two numbers = two monomers.

Trap 4: Nylon-6,6 linkage called "polyester"

• WRONG: Nylon-6,6 has ester linkages.
• CORRECT: Nylon-6,6 has AMIDE (–CO–NH–) linkages → polyAMIDE. Dacron has ESTER (–COO–) linkages → polyESTER.
• Memory: Dacron = Diacid + Diol = Ester. Nylon = diAmine + diacid = Amide.

Trap 5: Cl• in ozone depletion is consumed

• WRONG: "Each CFC molecule destroys only one O3 molecule."
• CORRECT: Cl• is the CATALYST — it is regenerated at the end of each cycle. One Cl• destroys ~100,000 O3 molecules.
• Memory: Cl• is never consumed; it is a catalytic radical.

Trap 6: Minamata and Itai-Itai disease confusion

• WRONG: Cadmium causes Minamata disease; mercury causes Itai-Itai disease.
• CORRECT: Mercury (Hg) → Minamata disease (neurological). Cadmium (Cd) → Itai-Itai disease (bone pain, kidney failure).
• Memory: Hg → Mi (both start with "M" in Japanese disease names). Cd → Itai (C and I are neighboring-ish).

Trap 7: Vulcanization makes rubber completely rigid

• WRONG: Vulcanization makes rubber rigid and non-elastic (like Bakelite).
• CORRECT: Vulcanization makes rubber HARDER but MORE consistently ELASTIC, less tacky. S–S cross-links prevent irreversible deformation but still allow chain extension and recoil.

Trap 8: Photochemical smog vs London smog effects

• WRONG: London smog causes eye irritation; photochemical smog causes respiratory problems from SO2.
• CORRECT: Photochemical smog → eye irritation (PAN). London smog → respiratory problems, poor visibility. Both can cause respiratory issues, but eye irritation is specifically photochemical smog.