Chemistry — Important Reactions
Chemical equations that appear in TGBIE 1st Year Chemistry exams — Redox, Hydrogen compounds, s-Block, p-Block, and Organic reactions. Based on official TGBIE Annual Plan 2025-26.
Ch. 5 Stoichiometry — Redox Reactions
2KMnO₄ + 8H₂SO₄ + 10FeSO₄ → K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O
Titration of FeSO₄ with KMnO₄ in acidic medium
2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → K₂SO₄ + 2MnSO₄ + 10CO₂ + 8H₂O
Oxalic acid titration — permanganate turns colourless
Cr₂O₇²⁻ + 6Fe²⁺ + 14H⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O
Dichromate as oxidising agent in acidic solution
Ch. 8 Hydrogen and its Compounds
2H₂O (electrolysis) → 2H₂ + O₂
Preparation of dihydrogen — electrolysis of water
Zn + H₂SO₄ → ZnSO₄ + H₂↑
Lab preparation of hydrogen — metal + dilute acid
2Na + 2H₂O → 2NaOH + H₂↑
Sodium reacts vigorously with water — alkali metal reaction
2H₂O₂ → 2H₂O + O₂
Decomposition of H₂O₂ — catalysed by MnO₂
H₂O₂ + 2KI + H₂SO₄ → I₂ + K₂SO₄ + 2H₂O
H₂O₂ as oxidising agent
2KMnO₄ + 5H₂O₂ + 3H₂SO₄ → 2MnSO₄ + K₂SO₄ + 8H₂O + 5O₂
H₂O₂ as reducing agent
Ch. 9 s-Block Elements
2Na + O₂ → Na₂O₂ (sodium peroxide)
Na burns in excess O₂
4Li + O₂ → 2Li₂O (lithium oxide)
Li forms only oxide, not peroxide
Na₂CO₃ + H₂O + CO₂ → 2NaHCO₃
Solvay process — CO₂ passed into brine with ammonia
2NaHCO₃ → Na₂CO₃ + H₂O + CO₂
Decomposition of baking soda on heating
CaO + H₂O → Ca(OH)₂
Slaking of lime
Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O
Limewater test for CO₂ — milky white precipitate
CaCO₃ → CaO + CO₂
Thermal decomposition of limestone — calcination
Ch. 10 & 11 p-Block Elements (Group 13 & 14)
B₂O₃ + 3Na₂CO₃ → 2Na₃BO₃ + 3CO₂
Preparation of sodium metaborate
Na₂B₄O₇ + 7H₂O → 4H₃BO₃ + 2NaOH
Hydrolysis of borax
B₂H₆ + 6H₂O → 2B(OH)₃ + 6H₂
Diborane hydrolysis
C + O₂ → CO₂; 2C + O₂ → 2CO (limited O₂)
Carbon combustion products
SiO₂ + 2NaOH → Na₂SiO₃ + H₂O
Silica dissolves in alkali
SiO₂ + HF → SiF₄ + 2H₂O
HF etches glass — SiO₂ attacked by HF, not other acids
Ch. 13 Organic Chemistry — Hydrocarbons
CH₄ + Cl₂ → CH₃Cl + HCl (UV light)
Free radical substitution — halogenation of alkane
CH₂=CH₂ + Br₂ → CH₂Br−CH₂Br
Addition of Br₂ to alkene — test for unsaturation (Br₂ water decolourises)
CH₂=CH₂ + HCl → CH₃CH₂Cl (Markovnikov's rule)
Addition of HX to alkene — H adds to C with more H
CH≡CH + H₂O → CH₃CHO (H₂SO₄/HgSO₄)
Hydration of acetylene — Markovnikov addition gives aldehyde
C₆H₆ + Cl₂ → C₆H₅Cl + HCl (FeCl₃ catalyst)
Electrophilic substitution of benzene — halogenation
C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O (H₂SO₄, 60°C)
Nitration of benzene — electrophilic substitution