CBSE Class 12 Chemistry All Reactions and Equations 2027 — PDF

In short: Chemistry reactions carry 15-20 marks in CBSE Class 12 board exam. This guide covers all important reactions from Organic, Inorganic, and Physical Chemistry — organized chapter-wise for quick revision.

Unit 1: Solid State

Defects in Solids

Schottky Defect: Equal number of cations and anions missing

• Density decreases
• Example: NaCl, KCl, AgBr

Frenkel Defect: Ion displaced to interstitial site

• Density remains same
• Example: AgCl, AgBr, ZnS

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Unit 2: Solutions

Colligative Properties Formulas

Relative Lowering of Vapour Pressure

(P° - P)/P° = n₂/(n₁ + n₂) ≈ n₂/n₁ (for dilute solutions)

Elevation in Boiling Point

ΔTb = Kb × m
Kb = RT²M/(1000 × ΔHvap)

Depression in Freezing Point

ΔTf = Kf × m

Osmotic Pressure

π = CRT = (n/V)RT

Van't Hoff Factor

i = (Observed colligative property)/(Calculated colligative property)

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Unit 3: Electrochemistry

Important Equations

Nernst Equation

E = E° - (RT/nF) ln Q
E = E° - (0.059/n) log Q (at 298K)

Relationship between ΔG and E

ΔG° = -nFE°

Conductivity

κ = 1/ρ (Unit: S/m)

Molar Conductivity

Λm = κ × 1000/M (Unit: S cm² mol⁻¹)

Kohlrausch's Law

Λ°m = λ°+ + λ°-

Faraday's Laws

m = ZIt = (M × I × t)/(n × F)
F = 96500 C/mol

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Unit 4: Chemical Kinetics

Rate Equations

Zero Order

[A] = [A]₀ - kt
t½ = [A]₀/2k

First Order

ln[A] = ln[A]₀ - kt
k = (2.303/t) log([A]₀/[A])
t½ = 0.693/k

Arrhenius Equation

k = Ae^(-Ea/RT)
log(k₂/k₁) = (Ea/2.303R)(1/T₁ - 1/T₂)

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Unit 5: Surface Chemistry

Adsorption Isotherms

Freundlich Isotherm

x/m = kP^(1/n)
log(x/m) = log k + (1/n)log P

Langmuir Isotherm

x/m = (aP)/(1 + bP)

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Unit 6: p-Block Elements (Groups 15-18)

Group 15 Reactions

Ammonia Preparation

2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃↑

Haber Process

N₂ + 3H₂ ⇌ 2NH₃ (Fe catalyst, 450°C, 200 atm)

Ostwald Process (HNO₃)

4NH₃ + 5O₂ → 4NO + 6H₂O (Pt catalyst)
2NO + O₂ → 2NO₂
3NO₂ + H₂O → 2HNO₃ + NO

Phosphorus Reactions

P₄ + 3O₂ → P₄O₆ (limited O₂)
P₄ + 5O₂ → P₄O₁₀ (excess O₂)
P₄O₁₀ + 6H₂O → 4H₃PO₄

Group 16 Reactions

Contact Process (H₂SO₄)

S + O₂ → SO₂
2SO₂ + O₂ ⇌ 2SO₃ (V₂O₅ catalyst)
SO₃ + H₂SO₄ → H₂S₂O₇ (Oleum)
H₂S₂O₇ + H₂O → 2H₂SO₄

Ozone Reactions

3O₂ → 2O₃ (UV light)
O₃ + 2KI + H₂O → 2KOH + I₂ + O₂

Group 17 Reactions

Chlorine Preparation

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O
2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 8H₂O + 5Cl₂

Bleaching Action

Cl₂ + H₂O → HCl + HOCl
HOCl → HCl + [O] (nascent oxygen bleaches)

Group 18 (Noble Gases)

Xenon Compounds

Xe + F₂ → XeF₂ (1:1, 400°C)
Xe + 2F₂ → XeF₄ (1:5, 400°C)
Xe + 3F₂ → XeF₆ (1:20, 300°C)

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Unit 7: d and f Block Elements

Important Reactions

Potassium Dichromate

K₂Cr₂O₇ + 4H₂SO₄ + 3SO₂ → K₂SO₄ + Cr₂(SO₄)₃ + 4H₂O
K₂Cr₂O₇ + 14HCl → 2KCl + 2CrCl₃ + 7H₂O + 3Cl₂

Potassium Permanganate

2KMnO₄ + 3H₂SO₄ + 5H₂C₂O₄ → K₂SO₄ + 2MnSO₄ + 8H₂O + 10CO₂
2KMnO₄ + 5FeSO₄ + 8H₂SO₄ → K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O

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Unit 8: Coordination Compounds

Nomenclature Rules

• Cation before anion
• Ligands in alphabetical order
• Oxidation state in Roman numerals

Examples:

• [Co(NH₃)₆]Cl₃ — Hexaamminecobalt(III) chloride
• K₄[Fe(CN)₆] — Potassium hexacyanoferrate(II)
• [Pt(NH₃)₂Cl₂] — Diamminedichloridoplatinum(II)

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Unit 9: Haloalkanes and Haloarenes

Nucleophilic Substitution Reactions

SN1 Mechanism (Tertiary halides)

(CH₃)₃C-Br + OH⁻ → (CH₃)₃C-OH + Br⁻
Rate = k[RX]

SN2 Mechanism (Primary halides)

CH₃-Br + OH⁻ → CH₃-OH + Br⁻
Rate = k[RX][Nu⁻]

Important Named Reactions

Wurtz Reaction

2R-X + 2Na → R-R + 2NaX (dry ether)
Example: 2CH₃Br + 2Na → C₂H₆ + 2NaBr

Wurtz-Fittig Reaction

C₆H₅Br + CH₃Br + 2Na → C₆H₅-CH₃ + 2NaBr

Fittig Reaction

2C₆H₅Br + 2Na → C₆H₅-C₆H₅ + 2NaBr

Finkelstein Reaction

R-Cl + NaI → R-I + NaCl (acetone)

Swarts Reaction

R-Cl + AgF → R-F + AgCl

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Unit 10: Alcohols, Phenols and Ethers

Alcohol Reactions

Dehydration

C₂H₅OH → C₂H₄ + H₂O (conc. H₂SO₄, 170°C)
2C₂H₅OH → C₂H₅-O-C₂H₅ + H₂O (conc. H₂SO₄, 140°C)

Oxidation

CH₃CH₂OH + [O] → CH₃CHO + H₂O (PCC)
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O (K₂Cr₂O₇/H⁺)

Phenol Reactions

Kolbe's Reaction

C₆H₅ONa + CO₂ + H₂O → o-HOC₆H₄COOH + NaOH (125°C, 4-7 atm)

Reimer-Tiemann Reaction

C₆H₅OH + CHCl₃ + 3NaOH → o-HOC₆H₄CHO + 3NaCl + 2H₂O

Williamson Synthesis

C₆H₅ONa + C₂H₅Br → C₆H₅OC₂H₅ + NaBr

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Unit 11: Aldehydes, Ketones and Carboxylic Acids

Aldehyde/Ketone Reactions

Aldol Condensation

2CH₃CHO → CH₃CH(OH)CH₂CHO (dilute NaOH)
         → CH₃CH=CHCHO + H₂O (heat)

Cannizzaro Reaction (aldehydes without α-H)

2HCHO + NaOH → HCOONa + CH₃OH
2C₆H₅CHO + NaOH → C₆H₅COONa + C₆H₅CH₂OH

Clemmensen Reduction

R-CO-R' + Zn-Hg/HCl → R-CH₂-R'

Wolff-Kishner Reduction

R-CO-R' + N₂H₄ + KOH → R-CH₂-R' + N₂ + H₂O

Carboxylic Acid Reactions

Hell-Volhard-Zelinsky Reaction

R-CH₂-COOH + Br₂/P → R-CHBr-COOH + HBr

Decarboxylation

R-COONa + NaOH → R-H + Na₂CO₃ (CaO, heat)

Kolbe Electrolysis

2CH₃COONa + 2H₂O → C₂H₆ + 2CO₂ + 2NaOH + H₂

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Unit 12: Amines

Preparation

Hoffmann Bromamide Reaction

R-CONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂CO₃ + 2NaBr + 2H₂O

Gabriel Phthalimide Synthesis

Phthalimide + KOH → Potassium phthalimide
Potassium phthalimide + R-X → N-alkyl phthalimide
N-alkyl phthalimide + NaOH/H₂O → R-NH₂ + Phthalic acid

Reactions

Carbylamine Reaction (Test for 1° amines)

R-NH₂ + CHCl₃ + 3KOH → R-NC + 3KCl + 3H₂O

Diazotization

C₆H₅NH₂ + NaNO₂ + 2HCl → C₆H₅N₂⁺Cl⁻ + NaCl + 2H₂O (0-5°C)

Sandmeyer Reaction

C₆H₅N₂⁺Cl⁻ + CuCl → C₆H₅Cl + N₂
C₆H₅N₂⁺Cl⁻ + CuBr → C₆H₅Br + N₂
C₆H₅N₂⁺Cl⁻ + CuCN → C₆H₅CN + N₂

Gattermann Reaction

C₆H₅N₂⁺Cl⁻ + Cu/HCl → C₆H₅Cl + N₂

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Unit 13: Biomolecules

Carbohydrate Reactions

Benedict's Test (Reducing sugars)

Glucose + Cu²⁺ (alkaline) → Red ppt of Cu₂O

Tollens' Test

Glucose + [Ag(NH₃)₂]⁺ → Silver mirror

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Quick Reference: Named Reactions

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Frequently Asked Questions

How many reactions should I memorize for CBSE Class 12 Chemistry?

Around 50-60 important reactions. Focus on Named Reactions (Wurtz, Aldol, Cannizzaro, etc.) and mechanism-based reactions.

Which chapters have the most reactions?

1. Haloalkanes and Haloarenes — 10+ reactions
2. Alcohols, Phenols, Ethers — 10+ reactions
3. Aldehydes, Ketones, Carboxylic Acids — 15+ reactions
4. Amines — 10+ reactions

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