Important Chemical Reactions
All key balanced chemical equations for BSE Telangana Class 10 Physical Science — acids and bases, metals, carbon compounds, decomposition, and salt preparation reactions.
Ch. 2 — Chemical Equations and Reactions
2H₂ + O₂ → 2H₂O
Combination reaction: two or more substances combine to form a single product
CaO + H₂O → Ca(OH)₂
Combination: quicklime + water → slaked lime (exothermic)
2H₂O → 2H₂ + O₂ (electrolysis)
Electrolytic decomposition of water
CaCO₃ → CaO + CO₂↑ (heat)
Thermal decomposition of limestone — used in cement industry
2Pb(NO₃)₂ → 2PbO + 4NO₂↑ + O₂↑ (heat)
Thermal decomposition of lead nitrate — brown fumes of NO₂
2AgCl → 2Ag + Cl₂↑ (sunlight)
Photolytic decomposition — principle behind black-and-white photography
2AgBr → 2Ag + Br₂↑ (sunlight)
Photolytic decomposition of silver bromide
Fe + CuSO₄ → FeSO₄ + Cu
Single displacement: Fe is more reactive than Cu — blue colour of solution fades
Zn + CuSO₄ → ZnSO₄ + Cu
Single displacement: Zn displaces Cu from its salt solution
Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl
Double displacement (precipitation): white precipitate of BaSO₄ formed
AgNO₃ + NaCl → AgCl↓ + NaNO₃
Double displacement: white precipitate of AgCl (curdy white)
Oxidation: loss of e⁻ / gain of O / loss of H; Reduction: gain of e⁻ / loss of O / gain of H
In redox reactions both happen simultaneously — oxidising agent gains electrons, reducing agent loses electrons
Ch. 3 — Acids, Bases and Salts
Zn + H₂SO₄ (dil.) → ZnSO₄ + H₂↑
Metal + dilute acid → salt + hydrogen gas
Mg + 2HCl → MgCl₂ + H₂↑
Magnesium reacts with hydrochloric acid
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑
Metal carbonate + acid → salt + water + CO₂
NaHCO₃ + HCl → NaCl + H₂O + CO₂↑
Baking soda + acid — CO₂ released (used in fire extinguishers)
HCl + NaOH → NaCl + H₂O
Neutralisation — acid + base → salt + water (ΔH negative)
H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O
Sulphuric acid neutralised by potassium hydroxide
NaCl + H₂SO₄ (conc.) → NaHSO₄ + HCl↑
Preparation of HCl gas — NaCl + conc. H₂SO₄ heated
Na₂CO₃ + CO₂ + H₂O → 2NaHCO₃
Washing soda absorbs CO₂ to form baking soda (Solvay process)
2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑ (heat)
Heating baking soda — used in baking (CO₂ makes dough rise)
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Preparation of bleaching powder from slaked lime + chlorine gas
Ch. 11 — Principles of Metallurgy
4Na + O₂ → 2Na₂O
Sodium (highly reactive) burns in oxygen — stored in kerosene
2Mg + O₂ → 2MgO
Magnesium burns with dazzling white flame in oxygen
3Fe + 2O₂ → Fe₃O₄
Iron burns in oxygen — forms tri-iron tetraoxide (not Fe₂O₃)
2Cu + O₂ → 2CuO
Copper oxidises on heating — black CuO formed
2ZnO + C → 2Zn + CO₂
Carbon reduction of zinc oxide — used for zinc of medium reactivity
Fe₂O₃ + 3CO → 2Fe + 3CO₂
Reduction of iron oxide by CO in a blast furnace
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe
Thermite reaction — Al reduces Fe₂O₃; highly exothermic, used in rail welding
Cu₂S + O₂ → 2Cu + SO₂
Roasting copper glance (Cu₂S) to get copper metal
4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O (rust)
Corrosion of iron — requires both O₂ and H₂O; prevented by galvanising or alloying
Ch. 12 — Carbon and Its Compounds
CH₄ + 2O₂ → CO₂ + 2H₂O
Complete combustion of methane — blue flame, used as cooking gas
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
Complete combustion of ethanol
CH₄ + Cl₂ → CH₃Cl + HCl (sunlight)
Substitution reaction of methane with chlorine — UV light required
CH₂=CH₂ + Br₂ → CH₂Br−CH₂Br
Addition reaction: ethene decolourises bromine water (test for alkene)
CH≡CH + 2H₂ → CH₃−CH₃ (Ni catalyst)
Addition of hydrogen (hydrogenation) to ethyne — used to harden oils
CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O (H₂SO₄ cat.)
Esterification — ethanoic acid + ethanol → ethyl ethanoate (fruity smell)
CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
Saponification: ester + base → soap (sodium salt) + alcohol
C₂H₅OH → CH₃CHO (oxidation, KMnO₄)
Mild oxidation of ethanol gives ethanal (aldehyde)
C₂H₅OH → C₂H₄ + H₂O (conc. H₂SO₄, 443 K)
Dehydration of ethanol to ethene — used in industrial ethylene production