CBSE Class 12 Chemistry All Name Reactions, Formulas & Distinction Tests
The comprehensive board examination cheat sheet covering Physical Chemistry numerical formulas, Inorganic coordination & d-block reaction tables, all 28 statutory Organic named reactions with reagents and mechanisms, and essential chemical distinction test matrices.
1. Solutions (Physical Chemistry • 7 Marks)
Raoult's Law, Colligative Properties, and Abnormal Molar Masses| Law / Property | Formula | Key Points & Constants |
|---|---|---|
| Henry's Law | p = K_H · x | Higher K_H means lower solubility of gas in liquid. K_H increases with temperature (aquatic life prefers cold water). |
| Raoult's Law | Volatile binary solution: P_total = P_A + P_B = P_A° x_A + P_B° x_B | Ideal solutions obey Raoult's law over entire range (ΔH_mix = 0, ΔV_mix = 0, e.g. Benzene + Toluene). |
| Relative Lowering of VP | (P_A° - P_A) / P_A° = x_B = (w_B / M_B) · (M_A / w_A) | Colligative property depending on number of solute particles, not nature. |
| Elevation in Boiling Point | ΔT_b = i · K_b · m = i · (1000 · K_b · w_B) / (M_B · w_A) | K_b = molal elevation constant (ebullioscopic constant). Water K_b = 0.52 K·kg/mol. |
| Depression in Freezing Point | ΔT_f = i · K_f · m = i · (1000 · K_f · w_B) / (M_B · w_A) | K_f = molal depression constant (cryoscopic constant). Water K_f = 1.86 K·kg/mol. Used in ethylene glycol anti-freeze. |
| Osmotic Pressure | Π = i · C R T = i · (w_B R T) / (M_B V) | Best colligative property for determining molecular masses of polymers & proteins because measurements are taken at room temperature and molarity is used. |
| Van 't Hoff Factor (i) & α | i = Normal Molar Mass / Abnormal Molar Mass Dissociation: α = (i - 1) / (n - 1) Association (dimer): α = (1 - i) / (1 - 1/n) |
For non-electrolyte (glucose, urea): i = 1. NaCl (i ≈ 2), BaCl₂ (i ≈ 3), K₄[Fe(CN)₆] (i ≈ 5). Acetic acid in benzene associates to dimer (i ≈ 0.5). |
2. Electrochemistry (Physical Chemistry • 9 Marks)
Galvanic Cells, Nernst Equation, Conductance & Electrolysis| Concept | Formula | Notes & Constants |
|---|---|---|
| Standard Cell Potential | E°_cell = E°_cathode - E°_anode (Reduction potentials) | Reaction is spontaneous if E°_cell > 0 (and ΔG° < 0). Anode is oxidation; cathode is reduction (An Ox, Red Cat). |
| Nernst Equation (at 298 K) | E_cell = E°_cell - (0.0591 / n) · log₁₀ Q Equilibrium: log₁₀ K_c = (n · E°_cell) / 0.0591 |
n = number of electrons exchanged in balanced redox reaction. Q = [Products] / [Reactants]. Pure solids and liquids have activity = 1. |
| Gibbs Energy & Electrical Work | ΔG° = -n F E°_cell = -2.303 R T log₁₀ K_c | F = Faraday's constant ≈ 96500 C/mol e⁻. Note: E°_cell is an intensive property; ΔG° is extensive. |
| Conductivity & Molar Conductivity | κ = (1/R) · (l/A) = G · G* Λ_m = (κ × 1000) / Molarity |
κ = conductivity (S·cm⁻¹), G* = cell constant (l/A in cm⁻¹), Λ_m = molar conductivity (S·cm²·mol⁻¹). Conductivity κ decreases on dilution; Molar conductivity Λ_m increases on dilution. |
| Kohlrausch's Law of Independent Migration | Λ°_m = ν₊ λ°₊ + ν₋ λ°₋ Degree of Dissociation: α = Λ_m / Λ°_m Dissociation Constant: K_a = (c · α²) / (1 - α) |
Used to calculate limiting molar conductivity Λ°_m for weak electrolytes like acetic acid using strong electrolyte data. |
| Faraday's Laws of Electrolysis | m = Z · I · t = (M · I · t) / (n · 96500) | 1 Faraday (96500 C) deposits 1 gram-equivalent of any substance (e.g. 1 mol Ag⁺, 0.5 mol Cu²⁺, 1/3 mol Al³⁺). |
3. Chemical Kinetics (Physical Chemistry • 7 Marks)
Reaction Rates, Integrated Rate Equations & Arrhenius Theory| Order | Integrated Rate Equation | Half-Life (t₁/₂) | Units of k |
|---|---|---|---|
| Zero Order | k = ([R]₀ - [R]) / t ⟹ [R] = -kt + [R]₀ | t₁/₂ = [R]₀ / (2k) (proportional to [R]₀) | mol·L⁻¹·s⁻¹ |
| First Order | k = (2.303 / t) · log₁₀([R]₀ / [R]) | t₁/₂ = 0.693 / k (independent of [R]₀!) | s⁻¹ or min⁻¹ |
| General n-th Order | - | t₁/₂ ∝ 1 / [R]₀^(n - 1) | (mol·L⁻¹)^(1 - n) · s⁻¹ |
| Arrhenius Equation | k = A · e^(-E_a / RT) log₁₀(k₂ / k₁) = [E_a / (2.303 R)] · [ (T₂ - T₁) / (T₁ T₂) ] |
R = 8.314 J·K⁻¹·mol⁻¹ E_a = activation energy (J/mol). Graph of ln k vs 1/T yields straight line with slope = -E_a/R. |
|
4 & 5. d- & f-Block Elements and Coordination Compounds
Inorganic Chemistry • 14 Marks Combined| Topic / Complex | Key Concept / Formula | Exam Application |
|---|---|---|
| Magnetic Moment (Spin-only) | μ = √[ n(n + 2) ] BM | n = number of unpaired electrons. Units: Bohr Magneton (BM). n=1 ⟹ 1.73 BM, n=2 ⟹ 2.83 BM, n=3 ⟹ 3.87 BM, n=4 ⟹ 4.90 BM, n=5 ⟹ 5.92 BM. |
| Lanthanoid Contraction | Steady decrease in atomic and ionic radii from La³⁺ to Lu³⁺ due to poor shielding of 4f electrons. | Consequence: Zr and Hf have nearly identical radii and properties; basic character of hydroxides decreases from La(OH)₃ to Lu(OH)₃. |
| K₂Cr₂O₇ Oxidizing Action (Acidic) | Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O (Orange to Green) | Oxidizes: Fe²⁺ → Fe³⁺; I⁻ → I₂; H₂S → S; Sn²⁺ → Sn⁴⁺. |
| KMnO₄ Oxidizing Action (Acidic) | MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O (Purple to Colorless) | Oxidizes: C₂O₄²⁻ (oxalate) → CO₂; Fe²⁺ → Fe³⁺; NO₂⁻ → NO₃⁻; I⁻ → I₂. |
| Coordination: VBT Hybridisation |
[Co(NH₃)₆]³⁺: d²sp³ (inner orbital, diamagnetic, low spin) [CoF₆]³⁻: sp³d² (outer orbital, paramagnetic, high spin) [Ni(CN)₄]²⁻: dsp² (square planar, diamagnetic) [NiCl₄]²⁻: sp³ (tetrahedral, paramagnetic, 2 unpaired e⁻) |
Strong field ligands (CN⁻, CO, NH₃) cause electron pairing; Weak field ligands (F⁻, Cl⁻, H₂O) do not pair electrons. |
| Crystal Field Splitting (CFSE) | Octahedral: Δ_o (t₂g lower, e_g higher) Tetrahedral: Δ_t = (4/9) Δ_o |
Spectrochemical series: I⁻ < Br⁻ < S²⁻ < Cl⁻ < NO₃⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < NO₂⁻ < CN⁻ < CO. If Δ_o > P, low spin (pairing); if Δ_o < P, high spin. |
6. All 28 Canonical Organic Named Reactions Master Suite
Organic Chemistry carries 33 Marks — Master every reagent, starting material, and mechanismReactant: Benzene diazonium chloride (Ar-N₂⁺Cl⁻)
Reagent: Cu₂Cl₂ / HCl or Cu₂Br₂ / HBr or CuCN / KCN
⭐ Iodobenzene is prepared simply by warming diazonium salt with KI without copper catalyst.
Reactant: Benzene diazonium chloride
Reagent: Copper powder (Cu) in presence of HCl or HBr
Yield is lower compared to Sandmeyer reaction.
Reactant: Alkyl chloride or bromide (R-Cl or R-Br)
Reagent: Sodium iodide (NaI) in dry acetone
NaCl/NaBr precipitates in dry acetone, driving equilibrium forward (Le Chatelier's principle).
Reactant: Alkyl chloride or bromide
Reagent: Heavy metallic fluoride (AgF, Hg₂F₂, CoF₃, or SbF₃)
The only convenient laboratory method to prepare alkyl fluorides.
Reactant: 2 molecules of Alkyl halide (R-X)
Reagent: Sodium metal (Na) in dry ether
Methane cannot be prepared; only good for symmetrical alkanes with even number of carbons.
Wurtz-Fittig: Ar-X + R-X + 2Na (dry ether) → Ar-R + 2NaX (Alkylarene)
Fittig: 2 Ar-X + 2Na (dry ether) → Ar-Ar (Diphenyl) + 2NaX
Reactant: Phenol (converted to Sodium phenoxide)
Reagents: 1. CO₂ (400 K, 4-7 atm) 2. H⁺ acidification
Salicylic acid is acetylated with (CH₃CO)₂O to manufacture Aspirin.
Reactant: Phenol
Reagents: Chloroform (CHCl₃) + aqueous NaOH, followed by H⁺
Electrophile is Dichlorocarbene (:CCl₂). If CCl₄ is used, Salicylic acid is formed.
Reactant: Alkyl halide + Sodium alkoxide (R'-ONa)
⭐ Follows S_N2 mechanism! Alkyl halide R-X must be 1° only. If 3° alkyl halide is used, elimination dominates to give alkene!
Reactant: Acyl chloride (Acid chloride R-COCl)
Reagents: H₂ over Pd poisoned with BaSO₄ (and sulfur/quinoline)
BaSO₄ acts as catalyst poison to prevent further reduction of aldehyde to alcohol.
Reactant: Nitrile (R-CN)
Reagents: SnCl₂ + HCl, followed by boiling with H₂O
Reactant: Toluene (C₆H₅CH₃)
Reagents: Chromyl chloride (CrO₂Cl₂) in CS₂, followed by H₃O⁺
Reactant: Benzene
Reagents: CO + HCl in presence of anhydrous AlCl₃ / CuCl
Clemmensen (Acidic): >C=O + Zn-Hg / conc. HCl → >CH₂ + H₂O
Wolff-Kishner (Basic): >C=O + NH₂NH₂ (Hydrazine) → Hydrazone + KOH/ethylene glycol (heat) → >CH₂ + N₂↑
Use Clemmensen for base-sensitive compounds; use Wolff-Kishner for acid-sensitive compounds.
Requirement: Aldehyde or ketone having at least one α-hydrogen
Reagent: Dilute alkali (dil. NaOH or Ba(OH)₂), followed by heat
Cross-aldol between two different aldehydes with α-H yields a mixture of 4 products.
Requirement: Aldehydes having NO α-hydrogen (HCHO, C₆H₅CHO, (CH₃)₃CCHO)
Reagent: Concentrated alkali (50% conc. KOH or NaOH)
Self-redox: one molecule reduces to alcohol, other oxidizes to carboxylic acid salt.
Requirement: Carboxylic acids having α-hydrogen
Reagents: X₂ (Cl₂ or Br₂) in presence of Red Phosphorus, then H₂O
Purpose: Preparation of pure Primary Aliphatic Amines (1° R-NH₂)
Steps: Phthalimide + ethanolic KOH → Potassium phthalimide + R-X → N-Alkylphthalimide + aq. NaOH → 1° Amine + Phthalate ion
⭐ Aromatic 1° amines (Aniline) CANNOT be prepared because aryl halides do not undergo nucleophilic substitution (S_N2) with phthalimide anion.
Reactant: Acid Amide (R-CONH₂)
Reagents: Bromine (Br₂) + ethanolic or aqueous NaOH / KOH
Crucial step-down reaction: Product amine contains one carbon less than starting amide!
Reactant: 1° Aliphatic or Aromatic Amine (R-NH₂ or Ar-NH₂)
Reagents: Chloroform (CHCl₃) + alcoholic KOH, warmed
Gives an extremely foul, obnoxious smell of isocyanide/carbylamine. 2° and 3° amines DO NOT show this test.
Diazotisation: C₆H₅NH₂ + NaNO₂ + 2 HCl (273–278 K) → C₆H₅N₂⁺Cl⁻ + NaCl + 2H₂O
Coupling with Phenol (pH 9-10): C₆H₅N₂⁺Cl⁻ + Phenol → p-Hydroxyazobenzene (Orange Dye)
Coupling with Aniline (pH 4-5): C₆H₅N₂⁺Cl⁻ + Aniline → p-Aminoazobenzene (Yellow Dye)
Alkylation: Ar-H + R-Cl (anh. AlCl₃) → Ar-R + HCl
Acylation: Ar-H + RCOCl (anh. AlCl₃) → Ar-COR (Acetophenone / Benzophenone)
⭐ Aniline does NOT undergo Friedel-Crafts reaction because basic -NH₂ group forms an insoluble salt with Lewis acid AlCl₃ catalyst!
7. Chemical Distinction Tests Master Matrix
Mandatory 2-mark & 3-mark questions in CBSE Board Papers Section B & C| Pair of Compounds | Chemical Test / Reagent | Observation for Compound A | Observation for Compound B |
|---|---|---|---|
| 1°, 2°, and 3° Alcohols | Lucas Test (Conc. HCl + anhyd. ZnCl₂) |
3° Alcohol: Turbidity appears immediately. 2° Alcohol: Turbidity appears within 5 minutes. |
1° Alcohol: Solution remains clear at room temperature (turbidity only on heating). |
| Methanol vs Ethanol | Iodoform Test (I₂ + NaOH, warm) |
Methanol: No yellow precipitate (does not have CH₃-CH(OH)- group). | Ethanol: Yellow crystalline precipitate of Iodoform (CHI₃) with antiseptic smell. |
| Phenol vs Alcohol (e.g. Ethanol) | Neutral FeCl₃ Test | Phenol: Violet / Purple coloration (forms iron-phenoxide complex). | Ethanol: No violet color change. |
| Phenol vs Benzoic Acid | Sodium Bicarbonate Test (Sat. NaHCO₃ solution) |
Phenol: No effervescence (too weak an acid to decompose NaHCO₃). | Benzoic Acid: Brisk effervescence with evolution of colorless CO₂ gas. |
| Aldehyde vs Ketone | Tollens' Test (Silver Mirror) [Ag(NH₃)₂]⁺ OH⁻ |
Aldehyde: Bright silver mirror on inner test tube walls. | Ketone: No silver mirror formed. |
| Acetaldehyde vs Benzaldehyde | Fehling's Solution or Iodoform Test | Acetaldehyde: Red precipitate of Cu₂O with Fehling's, and yellow CHI₃ ppt with I₂/NaOH. | Benzaldehyde: No red Cu₂O ppt (aromatic aldehydes do not reduce Fehling's) and no iodoform ppt. |
| Pentan-2-one vs Pentan-3-one | Iodoform Test (I₂ + NaOH, warm) |
Pentan-2-one: Bright yellow precipitate of CHI₃ (contains methyl ketone group CH₃-C=O). | Pentan-3-one: No yellow precipitate (no methyl ketone group). |
| 1° Amine vs 2° / 3° Amine | Carbylamine Test (CHCl₃ + alc. KOH, warm) |
1° Amine: Extremely foul, offensive smell of isocyanide. | 2° and 3° Amines: No offensive smell (negative test). |
| Aliphatic 1° Amine vs Aniline | Azo Dye Test (NaNO₂ + HCl at 0-5°C, then β-naphthol) |
Ethylamine: Rapid effervescence of N₂ gas with no dye formation. | Aniline: Brilliant orange-red azo dye precipitate formed. |
| 1°, 2°, and 3° Amines | Hinsberg Test (Benzenesulfonyl chloride C₆H₅SO₂Cl + aq. KOH) |
1° Amine: Precipitate forms which is soluble in alkali (KOH) due to acidic hydrogen on nitrogen. | 2° Amine: Precipitate forms which is insoluble in KOH. 3° Amine: Does not react at all. |
8. Biomolecules (Organic Chemistry • 7 Marks)
Carbohydrates, Amino Acids, Proteins & Nucleic Acids| Substance / Reaction | Reagents & Equations | Structural Deduction |
|---|---|---|
| Glucose + HI (heat) | Glucose + HI (Δ) → n-Hexane | Proves that all 6 carbon atoms in glucose are linked in a straight unbranched chain. |
| Glucose + NH₂OH / HCN | Forms Oxime with hydroxylamine; forms Cyanohydrin with HCN. | Confirms the presence of a carbonyl group (>C=O). |
| Glucose + Br₂ water | Glucose + Br₂ water → Gluconic acid (Mild oxidation) | Proves that the carbonyl group is an aldehyde group (-CHO), not a ketone. |
| Glucose + (CH₃CO)₂O | Forms Glucose Pentaacetate with acetic anhydride. | Confirms the presence of 5 hydroxyl groups (-OH) attached to 5 different carbon atoms. |
| Glucose + HNO₃ | Glucose + HNO₃ → Saccharic acid (Dicarboxylic acid) | Proves that the terminal sixth carbon is a primary alcohol group (-CH₂OH). |
| Peptide Linkage | -CO-NH- bond formed between -COOH of one amino acid and -NH₂ of another with elimination of H₂O. | Proteins are polymers of α-amino acids linked by peptide bonds. |
| Protein Denaturation | Physical (heat) or chemical (pH change) disruption of secondary and tertiary structures. | Hydrogen bonds break; protein coagulates. Primary structure remains intact (peptide bonds do not break!). Example: coagulation of egg white on boiling, curdling of milk. |
| DNA vs RNA |
DNA: β-D-2-deoxyribose sugar; Nitrogen bases: Adenine, Guanine, Cytosine, Thymine; Double helix. RNA: β-D-ribose sugar; Nitrogen bases: Adenine, Guanine, Cytosine, Uracil; Single strand. |
Base pairing in DNA: A=T (2 H-bonds) and G≡C (3 H-bonds). |