रासायनिक प्रतिक्रियाएँ और समीकरण

Chemical Reactions and Equations

• Word Equations: Show reactants and products in words. Example: Magnesium + Oxygen → Magnesium oxide.
• Balanced Equations: Show the same elements on both sides of an arrow with equal numbers of atoms. Example: 2Mg + O₂ → 2MgO
• Reaction Conditions: Conditions can appear above or below the arrow. Example: 340 atm, Sunlight, Catalyst
• Combination Reaction: Two or more reactants combine to form a single product. Examples: C(s) + O₂(g) → CO₂(g), 2H₂(g) + O₂(g) → 2H₂O(l)
• Exothermic Reactions: Reactions that release heat. Examples: Burning of natural gas (CH₄ + 2O₂ → CO₂ + 2H₂O + Heat), Respiration (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy)

Decomposition Reaction

• Decomposition Reaction: A compound splits into two or more simpler substances.
• Thermal Decomposition: Decomposition caused by heating. Examples: 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g), CaCO₃(s) → CaO(s) + CO₂(g)
• Electrolytic Decomposition: Decomposition using electricity. Example: 2H₂O(l) → 2H₂(g) + O₂(g)
• Photolytic Decomposition: Decomposition with sunlight. Example: 2AgCl(s) → 2Ag(s) + Cl₂(g)

Endothermic Reactions

• Endothermic Reactions: Reactions that absorb energy.

Displacement Reaction

• Displacement Reaction: A more reactive element replaces a less reactive element in a compound. Example: Fe + CuSO₄ → FeSO₄ + Cu

Double Displacement Reaction

• Double Displacement Reaction: New compounds are formed by the mutual exchange of ions. Example: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq) , precipitation of BaSO₄ forms

Oxidation and Reduction (Redox)

• Oxidation: Gain of oxygen or loss of electrons. Example: 2Cu + O₂ → 2CuO
• Reduction: Loss of oxygen or gain of electrons. Example: CuO + H₂ → Cu + H₂O
• Redox Reactions: Reactions involving both oxidation and reduction. Example: MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O

Acids, Bases and Salts

• Acids with Metals: Acid + Metal → Salt + Hydrogen gas . Example: 2HCl + Zn → ZnCl₂ + H₂
• Acids with Metal Carbonates/Hydrogen Carbonates: Acid + Metal Carbonate/Hydrogen Carbonate → Salt + CO₂ + H₂O . Example: 2HCl + Na₂CO₃ → 2NaCl + CO₂+ H₂O
• Testing for CO₂: Pass CO₂ through limewater (Ca(OH)₂), it turns milky
• Acids and Bases with Each Other: Acid + Base → Salt + Water. Example: NaOH(aq) + HCl(aq) → NaCl(aq)+ H₂O(l).
• Common property of acids: Dissociate into H+ ions in water

Metals and Non-metals

• Metals with Air: Metals + Oxygen → Metal Oxide . Example: 2Cu + O₂ → 2CuO
• Amphoteric Oxides: Metal oxides that react with both acids and bases. Example: Al₂O₃
• Metals with Water: Metals + Water → Metal Hydroxide + Hydrogen gas. Example: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)
• Metals with steam: Metals like aluminum, iron and zinc do not react with water but reacts with steam to form metal oxide and hydrogen gas
• Extraction of Metals: Processes to obtain metals from their ores. Examples: Roasting, and Calcination(Heating ore in absence of air)

Extracting Metals

• Roasting: Heating metal sulfide ores in air to produce metal oxides. Example: 2ZnS + 3O₂ → 2ZnO + 2SO₂
• Calcination: Heating carbonate ores in absence of air. Example: ZnCO₃ → ZnO + CO₂
• Electrolytic Reduction: Using electricity to reduce metal ions to obtain metals. Example: Na+ + e− → Na
• Thermite Reaction: A highly exothermic reaction using aluminum to reduce metal oxides. Example: Fe₂O₃ + 2Al → 2Fe + Al₂O₃