CBSE · Class 10 · Chemistry · Chapter 1

Chemical Reactions and Equations — Formula Sheet

Board Formulas

8 formulas

1.General Combination Reaction★
$A + B ⟶ A B$
Two or more reactants combine to form a single product. Often exothermic. Example: CaO + H₂O → Ca(OH)₂.
2.General Decomposition Reaction★
$A B ⟶ A + B$
A single reactant breaks into two or more products. Requires heat / light / electricity. Endothermic.
3.Thermal Decomposition of Calcium Carbonate
$C a C O_{3} (s) Δ C a O (s) + C O_{2} (g)$
Basis of lime industry. Products: quicklime (CaO) and carbon dioxide.
4.Displacement Reaction
$A + B C ⟶ A C + B$
More reactive element A displaces less reactive B. Example: Fe + CuSO₄ → FeSO₄ + Cu (blue → green).
5.Double-Displacement (Precipitation)★
$A B + C D ⟶ A D + C B$
Ions swap partners; often produces an insoluble precipitate. Example: Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2 NaCl.
6.Photochemical Decomposition of AgCl
$2 A g C l (s) h ν 2 A g (s) + C l_{2} (g)$
White silver chloride turns grey in sunlight — basis of black-and-white photography.
7.Oxidation and Reduction (Redox)
$oxidation loss of e^{-} ∣∣ reduction gain of e^{-}$
Redox = oxidation + reduction happen together. Mnemonic: OIL RIG — Oxidation Is Loss, Reduction Is Gain (of electrons).
8.Formation of Rust
$4 F e (s) + 3 O_{2} (g) + 2 x H_{2} O ⟶ 2 F e_{2} O_{3} \cdot x H_{2} O (s)$
Rust needs BOTH oxygen and water. Prevention: painting, galvanising, alloying (stainless steel).