In short: Class 12 Chemistry is a mix of Physical Chemistry formulas, named organic reactions, and coordination chemistry concepts. This complete reference covers every important formula and reaction from all 16 chapters, organised for quick revision. Whether you are preparing for CBSE 2027 boards or NEET, this is your one-stop formula and reaction sheet.
The Three Pillars of Class 12 Chemistry
Class 12 Chemistry splits into three sections in the board exam: Physical Chemistry (~23 marks), Inorganic Chemistry (~19 marks), and Organic Chemistry (~28 marks). Each section requires a different type of preparation.
Physical Chemistry needs mathematical formulas. Organic Chemistry needs named reactions and conversion mechanisms. Inorganic Chemistry needs factual recall and trends.
This sheet covers all three, chapter by chapter.
Part 1 - Physical Chemistry
Chapter 1 - Solutions
| Formula | Expression | Unit |
|---|---|---|
| Molarity | M = Moles of solute / Volume of solution (L) | mol/L |
| Molality | m = Moles of solute / Mass of solvent (kg) | mol/kg |
| Mole fraction | x(A) = n(A) / (n(A) + n(B)) | Dimensionless |
| Raoult's law | P(A) = x(A) P(A)* (P* = vapour pressure of pure component) | Pa |
| Relative lowering of vapour pressure | (P* - P) / P* = x(solute) = n(B) / (n(A) + n(B)) | Dimensionless |
| Elevation of boiling point | Delta T(b) = K(b) m | K |
| Depression of freezing point | Delta T(f) = K(f) m | K |
| Osmotic pressure | pi = CRT = (n/V)RT | Pa |
| van't Hoff factor | i = Observed colligative property / Calculated colligative property | Dimensionless |
| Modified formula with i | Delta T(b) = i K(b) m | K |
| Henry's law | p = K(H) x (gas pressure proportional to mole fraction) | Pa |
Chapter 2 - Electrochemistry
| Formula | Expression | Unit |
|---|---|---|
| Nernst equation (cell) | E(cell) = E(cell)* - (RT/nF) ln Q | V |
| Nernst equation (25 C) | E(cell) = E(cell)* - (0.0591/n) log Q | V |
| Gibbs energy and EMF | Delta G = -nFE(cell) | J |
| Relation | Delta G* = -nFE(cell)* = -RT ln K | J |
| Conductance | G = 1/R = kappa A/l | S (Siemens) |
| Conductivity | kappa = 1/rho = G l/A | S/m |
| Molar conductivity | Lambda(m) = kappa x 1000 / M (M in mol/L) | S cm^2/mol |
| Kohlrausch's law | Lambda(m)* = v(+) lambda(+)* + v(-) lambda(-)* | S cm^2/mol |
| Faraday's first law | m = ZIt = (MIt)/(nF) | g |
| Faraday's second law | m1/m2 = E1/E2 (equivalent weights) | - |
| 1 Faraday | F = 96485 C/mol ~96500 C/mol | C/mol |
Chapter 3 - Chemical Kinetics
| Formula | Expression | Unit |
|---|---|---|
| Average rate | Rate = -Delta[R]/Delta t = Delta[P]/Delta t | mol/(L s) |
| Rate law | Rate = k [A]^m [B]^n | mol/(L s) |
| Zero order rate constant | k = [A]0 - [A]t / t | mol/(L s) |
| Zero order half-life | t(1/2) = [A]0 / (2k) | s |
| First order rate constant | k = (2.303/t) log([A]0/[A]t) | s^-1 |
| First order half-life | t(1/2) = 0.693 / k | s |
| Arrhenius equation | k = A e^(-Ea/RT) | - |
| Arrhenius (log form) | log(k2/k1) = (Ea/2.303R)(1/T1 - 1/T2) | - |
| Activation energy | Ea = threshold energy - average energy | J/mol |
Chapter 4 - Surface Chemistry
| Concept | Formula / Key Fact |
|---|---|
| Freundlich adsorption isotherm | x/m = k P^(1/n), where 0 < 1/n < 1 |
| Freundlich (log form) | log(x/m) = log k + (1/n) log P |
| Coagulation | Adding electrolyte neutralises charge |
| Hardy-Schulze rule | Higher valency of flocculating ion = greater coagulation power |
Part 2 - Inorganic Chemistry
Chapter 5 - General Principles of Isolation of Elements
| Process | Key Fact |
|---|---|
| Concentration methods | Gravity separation, froth floatation, magnetic separation, leaching |
| Froth floatation | Used for sulphide ores (collectors: pine oil, xanthates) |
| Thermodynamic principle | Delta G = Delta H - T Delta S must be negative for spontaneous reduction |
| Ellingham diagram | Lower oxide line = more stable oxide; C line slopes downward = better reducing agent at high T |
| Electrolytic reduction | Used for Al (Hall-Heroult), Na, Ca |
| Zone refining | For semiconductors (Ge, Si, Ga) |
| Van Arkel method | For Zr, Ti (uses volatile compound formation and decomposition) |
Chapter 6 - p-Block Elements
| Group | Elements | Key Compounds / Reactions |
|---|---|---|
| Group 15 | N, P, As, Sb, Bi | NH3, HNO3, H3PO4 |
| Group 16 | O, S, Se, Te, Po | H2SO4, SO2, H2S |
| Group 17 | F, Cl, Br, I, At | HCl, Cl2, interhalogen compounds |
| Group 18 | He, Ne, Ar, Kr, Xe, Rn | XeF2, XeF4, XeF6 |
| Key Reaction | Equation |
|---|---|
| Ostwald process | 4NH3 + 5O2 -> 4NO + 6H2O (Pt catalyst, 500 K) |
| Contact process | 2SO2 + O2 -> 2SO3 (V2O5 catalyst) then SO3 + H2SO4 -> H2S2O7 |
| Deacon's process | 4HCl + O2 -> 2Cl2 + 2H2O (CuCl2 catalyst, 723 K) |
Chapter 7 - d and f Block Elements
| Property | Key Fact |
|---|---|
| Electronic configuration | (n-1)d^(1-10) ns^(1-2) |
| Variable oxidation states | Due to involvement of both ns and (n-1)d electrons |
| Most common oxidation state | +2 (removal of ns electrons) |
| Highest oxidation state | Mn (+7 in KMnO4) |
| Coloured compounds | Due to d-d transitions |
| Magnetic nature | Paramagnetic when unpaired electrons present |
| Spin-only magnetic moment | mu = sqrt(n(n+2)) BM, where n = unpaired electrons |
| Lanthanoid contraction | Gradual decrease in size across lanthanoid series due to poor shielding of 4f electrons |
Chapter 8 - Coordination Compounds
| Formula / Concept | Expression |
|---|---|
| Coordination number | Number of ligand donor atoms bonded to central metal |
| EAN (effective atomic number) | EAN = Z - oxidation state + 2 x coordination number |
| IUPAC naming order | Cation first, then anion; ligands alphabetical within complex |
| Crystal Field Splitting (octahedral) | Delta(o): t2g (lower) and eg (upper) |
| Crystal Field Splitting (tetrahedral) | Delta(t) = (4/9) Delta(o) |
| Spectrochemical series | I- < Br- < Cl- < F- < OH- < H2O < NH3 < en < NO2- < CN- < CO |
| CFSE | Stabilisation energy from crystal field splitting |
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Part 3 - Organic Chemistry
Named Reactions - Complete List
This is the most exam-critical section. CBSE asks 2-4 named reactions every year.
| Reaction Name | What It Does | Reagents |
|---|---|---|
| Sandmeyer reaction | ArN2+ to ArCl, ArBr, ArCN | CuCl/HCl, CuBr/HBr, CuCN/KCN |
| Gattermann reaction | ArN2+ to ArCl | Cu/HCl |
| Finkelstein reaction | RCl/RBr to RI | NaI in acetone |
| Swarts reaction | RCl to RF | AgF or Hg2F2 |
| Wurtz reaction | 2RX + 2Na to R-R | Na in dry ether |
| Wurtz-Fittig reaction | RX + ArX + 2Na to R-Ar | Na in dry ether |
| Fittig reaction | 2ArX + 2Na to Ar-Ar | Na in dry ether |
| Kolbe's reaction | Phenol + CO2/NaOH to salicylic acid | CO2 + NaOH (125 C, 4-7 atm) |
| Reimer-Tiemann reaction | Phenol + CHCl3/NaOH to salicylaldehyde | CHCl3 + NaOH |
| Williamson synthesis | RONa + RX to R-O-R (ether) | Na alkoxide + alkyl halide |
| Aldol condensation | 2 molecules of aldehyde with alpha-H to beta-hydroxy aldehyde | Dilute NaOH |
| Cannizzaro reaction | Aldehyde without alpha-H gives acid + alcohol | Conc. NaOH |
| Clemmensen reduction | C=O to CH2 | Zn-Hg/conc. HCl |
| Wolff-Kishner reduction | C=O to CH2 | NH2NH2/KOH/ethylene glycol |
| Rosenmund reduction | RCOCl to RCHO | H2/Pd-BaSO4 |
| Stephen reduction | RCN to RCHO | SnCl2/HCl |
| Hell-Volhard-Zelinsky | Alpha-halogenation of carboxylic acids | X2/red P |
| Hoffmann bromamide | RCONH2 to RNH2 (one C less) | Br2/NaOH |
| Gabriel phthalimide | Phthalimide + RX to primary amine | KOH then RX then hydrolysis |
| Carbylamine test | Primary amine gives isocyanide smell | CHCl3 + KOH |
| Diazotisation | ArNH2 to ArN2+Cl- | NaNO2 + HCl at 273-278 K |
| Coupling reaction | ArN2+ + ArOH/ArNH2 to azo dye | Diazonium salt + phenol/amine |
Chapter 9 - Haloalkanes and Haloarenes
| Formula / Concept | Detail |
|---|---|
| SN1 mechanism | 2 steps, carbocation intermediate, racemisation, favoured by 3 degree RX |
| SN2 mechanism | 1 step, backside attack, inversion (Walden), favoured by 1 degree RX, CH3X |
| Reactivity order (SN1) | 3 degree > 2 degree > 1 degree > CH3X |
| Reactivity order (SN2) | CH3X > 1 degree > 2 degree > 3 degree |
| Elimination (E1, E2) | Forms alkene, Saytzeff rule: more substituted alkene preferred |
Chapter 10 - Alcohols, Phenols and Ethers
| Key Reaction | Detail |
|---|---|
| Acidity order | Phenol > Water > Alcohol (due to resonance stabilisation of phenoxide) |
| Lucas test | 3 degree: immediate turbidity, 2 degree: 5 min, 1 degree: no reaction at RT |
| Alcohol to alkene | Dehydration with conc. H2SO4 at 443 K |
| Alcohol to aldehyde | 1 degree alcohol + PCC or CrO3-pyridine |
| Phenol reactions | Kolbe, Reimer-Tiemann, nitration, halogenation |
Chapter 11 - Aldehydes, Ketones and Carboxylic Acids
| Reaction / Test | Detail |
|---|---|
| Tollens test | Aldehyde + [Ag(NH3)2]+ gives silver mirror |
| Fehling test | Aldehyde + Cu^2+ gives red precipitate of Cu2O |
| Iodoform test | Methyl ketone (CH3CO-) or CH3CH(OH)- gives CHI3 (yellow) |
| Nucleophilic addition | Aldehydes more reactive than ketones (less steric hindrance) |
| Relative acidity of carboxylic acids | Electron-withdrawing groups increase acidity |
Chapters 12-16 - Amines, Biomolecules, Polymers, Chemistry in Everyday Life
| Topic | Key Fact |
|---|---|
| Amine basicity order (gas phase) | 3 degree > 2 degree > 1 degree > NH3 |
| Amine basicity order (aqueous) | 2 degree > 1 degree > 3 degree > NH3 (in most cases) |
| Carbohydrates | Monosaccharides (glucose, fructose), Disaccharides (sucrose, lactose), Polysaccharides (starch, cellulose) |
| Glucose open chain formula | CH2OH(CHOH)4CHO |
| Essential amino acids | 10 (cannot be synthesised by body) |
| Peptide bond | -CO-NH- bond between amino acids |
| DNA structure | Double helix, A=T (2 H-bonds), G≡C (3 H-bonds) |
| Addition polymers | Polythene, PVC, polystyrene, Teflon |
| Condensation polymers | Nylon-6,6, Bakelite, Dacron |
| Nylon-6,6 monomers | Adipic acid + hexamethylenediamine |
| Drugs | Analgesics (aspirin), Antibiotics (penicillin), Antiseptics (Dettol), Antacids (ranitidine) |
How to Memorise Chemistry Formulas and Reactions
1. Physical Chemistry - solve numericals. Nernst equation, rate law, colligative properties - each formula needs 5-10 practice problems to stick. You cannot memorise Delta G = -nFE without using it.
2. Named reactions - make a reaction card deck. Write the reaction name on one side, the transformation + reagent on the other. Shuffle and test yourself. After 3 rounds, you will remember 80% of them.
3. Organic conversions - draw reaction maps. Start with alkane, draw arrows to all possible products (alkene, alkyl halide, alcohol, aldehyde, acid, amine). Each arrow is a reagent. One diagram captures 10+ reactions.
4. Inorganic Chemistry - use comparison tables. Compare Group 15, 16, and 17 properties side by side. Patterns emerge (acidity increases across period, metallic character increases down group).
5. Use Padhaao for targeted testing. Ask the AI tutor to quiz you on named reactions or electrochemistry numericals. It gives instant feedback and explains errors in real time.
Common Mistakes in Class 12 Chemistry
- Forgetting the van't Hoff factor. For electrolytes (NaCl, CaCl2), colligative properties must be multiplied by i. NaCl dissociates into 2 ions, so i = 2. Forgetting this gives half the correct answer.
- Wrong sign in Nernst equation. E(cell) = E* - (0.0591/n) log Q. At 25 C. The minus sign means cell potential decreases as Q increases. Getting the sign wrong inverts your answer.
- Confusing SN1 and SN2. SN1: 3 degree substrate, polar protic solvent, racemisation. SN2: 1 degree substrate, polar aprotic solvent, inversion. Swapping them is a guaranteed mark loss.
- Mixing up Clemmensen and Wolff-Kishner. Clemmensen uses Zn-Hg/HCl (acidic conditions). Wolff-Kishner uses NH2NH2/KOH (basic conditions). Both reduce C=O to CH2, but the conditions differ.
- Forgetting units in kinetics. Zero order k has units mol/(L s). First order k has units s^-1. Second order k has units L/(mol s). The unit of k changes with the order of reaction.
Exam-Day Quick Revision Strategy
Minutes 1-10: Physical Chemistry formulas - Nernst equation, colligative properties (Delta Tb, Delta Tf, osmotic pressure), rate law, and Arrhenius equation.
Minutes 11-20: Named reactions. Run through the full list mentally: Sandmeyer, Kolbe, Reimer-Tiemann, Aldol, Cannizzaro, Clemmensen, Wolff-Kishner, Rosenmund, Hoffmann, Gabriel, Carbylamine. If you can recall all of these, you are ready.
Minutes 21-30: Inorganic Chemistry - d-block properties, coordination compound naming rules, spectrochemical series.
Minutes 31-35: Quick scan of polymer types, biomolecule classifications, and SN1/SN2 differences. Close the sheet and breathe.
FAQ
How many named reactions are in Class 12 Chemistry?
About 20-22 named reactions are commonly tested in CBSE boards. The most frequently asked ones are Sandmeyer, Kolbe, Aldol condensation, Cannizzaro, Williamson synthesis, and Hoffmann bromamide.
Which is the hardest chapter in Class 12 Chemistry?
Most students find Electrochemistry (Physical) and Coordination Compounds (Inorganic) the hardest. Electrochemistry has many interconnected formulas, and Coordination Chemistry requires understanding crystal field theory.
Should I memorise all named reactions or just the important ones?
Memorise all 20+ named reactions. CBSE rotates which ones it asks, and in NEET, any reaction can appear. The good news is they are all one-liners - reagent + substrate gives product. Flashcards make this easy.
Are Class 12 Chemistry formulas the same for NEET?
Yes. NEET Chemistry is entirely NCERT-based. The formulas and reactions in this sheet cover everything NEET tests in Chemistry. For Physical Chemistry, practise more numericals at NEET difficulty level.
How do I remember the spectrochemical series?
Mnemonic: "I Bring Chlorine For Our House, Not Nasty Cockroaches" - I- < Br- < Cl- < F- < OH- < H2O < NH3 < NO2- < CN- < CO. Create your own version if this one does not stick.
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