24 hours to exam? This page tells you exactly what to focus on, what to skip, and how to manage your time tomorrow.
CBSE Class 12 Chemistry
24 Hours Before the Exam
No time for everything. This guide tells you exactly what to revise, which topics almost certainly appear, what mistakes to avoid, and how to manage your 3 hours in the exam hall.
Focus on These Chapters First
- Electrochemistry — EMF calculation, Nernst equation, Kohlrausch's law
- Chemical Kinetics — rate law, order of reaction, half-life, Arrhenius equation
- Coordination Compounds — IUPAC naming, EAN rule, isomerism types
- Aldehydes & Ketones — nucleophilic addition, Cannizzaro, aldol condensation
- Amines — basicity order, reactions, Gabriel synthesis, Hinsberg test
- Haloalkanes — SN1 vs SN2 mechanism, Walden inversion
- d & f Block Elements — properties, oxidation states, colour, magnetic moment
- Solutions — Raoult's law, colligative properties, van't Hoff factor
Key Formulas & Facts to Memorise Right Now
- Nernst equation: E = E° - (RT/nF)lnQ | at 298K: E = E° - (0.0592/n)logQ
- Rate law: rate = k[A]ᵐ[B]ⁿ | Half-life (1st order): t½ = 0.693/k
- Arrhenius: k = Ae^(-Ea/RT) | log(k₂/k₁) = (Ea/2.303R)(1/T₁ - 1/T₂)
- Raoult's law: PA = xA × PA° | Relative lowering of VP: (PA°-PA)/PA° = xB
- Osmotic pressure: π = CRT | Elevation of BP: ΔTb = Kb × m
- CFSE for octahedral: d⁰ d⁵ (high spin) d¹⁰ = 0 | d³ d⁸ = maximum
- Magnetic moment: μ = √[n(n+2)] BM where n = number of unpaired electrons
Timing Strategy for 3 hours Exam
- 10–30 min: All MCQs and assertion-reason — Chemistry MCQs are memory-based, quick
- 230–80 min: 2-mark and 3-mark — conversions, reactions, mechanism outlines
- 380–150 min: 5-mark — full mechanisms, derivations, numerical problems
- 4150–170 min: Case study — usually organic chemistry in recent years
- 5Last 10 min: Check IUPAC names, state symbols, and numerical units
Common Mistakes — Avoid These Tomorrow
- ✕Writing incorrect IUPAC names — use the correct prefix order for ligands (alphabetical)
- ✕Confusing SN1 and SN2 — SN1 is for tertiary, SN2 for primary substrates
- ✕Forgetting to include state symbols in chemical equations
- ✕Not mentioning conditions (temperature, catalyst) above reaction arrows
- ✕Confusing oxidation state with oxidation number of metal in coordination compounds
- ✕Skipping units in electrochemistry — EMF in volts, rate constant units change with order
Must Attempt — Never Leave These Blank
- ✓All conversion reactions (organic) — follow functional group logic
- ✓Electrochemistry numericals — direct formula substitution
- ✓Coordination compound IUPAC naming — follows a strict rule, practice pays
- ✓Kinetics numericals — rate law and half-life are standard formulas
Skip If Unsure (Return If Time Permits)
- →Complex solid state packing problems if you're short on time
- →Uncommon polymer classification if you haven't memorised them
Remember: Partial marks exist. Attempt and leave if stuck — come back if time allows. Never spend more than 8 minutes on a single 5-mark question.
Chemistry is 60% memory and 40% logic. If you know your reactions and mechanisms, you can answer most questions even if you don't remember every detail — the logic flows.
Night Before — Non-Academic Checklist
Pack your bag
Admit card, 2 pens, pencil, eraser, ruler, geometry box (if needed)
Sleep by 10 PM
Your brain consolidates memory during sleep. Late-night cramming hurts more than it helps
Stop studying at 9 PM
Whatever you don't know by tonight won't be learnt in an hour. Trust your preparation
Set two alarms
One to wake up, one as a backup. Arrive at the centre 30 minutes before the exam
More resources for Class 12 Chemistry
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