Chemical Reactions and Equations Notes PDF

PRASHANT KIRAD Chemical Reactions and Equations Kuch important terms: →Precipitate: Insoluble solid formed after a Chemical Reaction: The transformation of chemical substance into anothe...

PRASHANT KIRAD Chemical Reactions and Equations Kuch important terms: →Precipitate: Insoluble solid formed after a Chemical Reaction: The transformation of chemical substance into another chemical substance. e.g. Rusting of iron, the setting chemical reaction. of milk into curd. →Exothermic Reaction: Reaction releasing heat Chemical Equation: Representation of chemical reaction using energy. symbols and formulae of the substances. →Endothermic Reaction: Reaction absorbing heat Reactant A+B →C+D Product energy. →Catalyst: Speeds up a reaction without being Reactant Mg + O2 → MgO Product consumed. Characteristic Example Reaction Balanced Chemical Equation: Number of atoms of each element in reactants = number of atoms of each element Change in Colour Fe + CuSO₄(Blue) → FeSO₄(Blue-green) + Cu in products. Law of Conservation of Mass: Mass of reactants = Mass of products Change in CaO + H₂O → Ca(OH)₂ + Heat (heat is generated) Balance these: Fe + H₂O → Fe₃O₄ + H₂ Temperature C₆H₁₂O₆ + O₂ → CO₂ + H₂O Change in State H₂(g) + O₂(g) → H₂O(l) (i.e., gas to liquid) Draw boxes around formulas. Count atoms on both sides. Evolution of Gas Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) Start with the biggest compound. Balance elements one by one. Formation of Use smallest whole numbers. Pb(NO₃)₂(aq) + KI(aq) → PbI₂(s) + KNO₃(aq) Precipitate Recheck for balance. Endothermic Types of Chemical Reactions: CaCO₃ + Heat → CaO + CO₂ (photosynthesis also) Reaction 1.Combination Reaction: Two or more reactants combine to form single products. Exothermic CaO + H₂O → Ca(OH)₂ + Heat (digestion and Reaction respiration also) A + B → AB The most effective way to test for CO₂ is to bubble the 3.Displacement Reaction: a more reactive element gas through lime water, which is a diluted solution of displaces a less reactive element from its compound. calcium hydroxide. Single Displacement A + BC → AC + B 2.Decomposition Reaction: A single reactant decomposes to form two or more products. Double Displacement AB + CD → AD + CB AB → A + B Reaction Observation Thermal Decomposition CaCO₃ → CaO + CO₂ Mg + O₂ → MgO Magnesium ribbon burns with a (thermal energy) dazzling white flame and forms a white powder (magnesium oxide). Photolytic Decomposition 2AgBr → 2Ag + Br₂ Yellow precipitate of lead (energy from sunlight) black & white photography Pb(NO₃)₂ + KI → PbI₂ iodide forms, and the solution Electrolytic Decomposition 2H₂O → 2H₂ + O₂ changes from colorless to electrical energy) yellow. Zn + H₂SO₄ → ZnSO₄ + H₂ Bubbles of hydrogen gas form around the zinc Hydrogen (cathode) will metal. Heat is released produce a popping sound during the reaction. when a burning candle is CaO + H₂O → Ca(OH)₂ Calcium oxide reacts brought close. Oxygen (anode) will vigorously with water to make the flame of the produce slaked lime, releasing candle burn brighter. a large amount of heat. 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ Initially green; turns white, then brown (ferric oxide) with the smell of burning sulfur. Reaction Observation 2AgCl → 2Ag + Cl₂ White silver chloride turns (in sunlight) grey in sunlight. The deep blue solution fades to Fe + CuSO₄ → light green, and the iron nail FeSO₄ + Cu becomes covered with a red- brown layer of copper. Rancidity: the spoilage of fats and oils in food, leading to unpleasant taste and smell. Na₂SO₄ + BaCl₂ → A white precipitate of Examples: Spoiled butter, Old cooking oil, BaSO₄ + 2NaCl barium sulfate forms. Stale chips Prevention: Adding antioxidants, storing Black copper oxide (CuO) foods in airtight containers, and 2Cu + O₂ → 2CuO forms. Hydrogen gas can refrigerating can help slow down or prevent reduce CuO back to copper the oxidation process and, consequently, during a reverse reaction. rancidity 4. Redox Reactions: Oxidation: + oxygen or - hydrogen Effects of oxidation in daily life: Reduction: - oxygen or + hydrogen Corrosion: metals are gradually destroyed by chemical reactions with substances in their environment, such as Oxidizing agent: An oxidizing agent is a substance moisture and acids. Examples: Rusting of iron, that causes oxidation by accepting electrons; Tarnishing of silver, Green coating on copper therefore, it gets reduced. Prevention: Coating metals with protective layers (e.g., Reducing agent: A reducing agent is a substance paint or galvanization) helps prevent direct exposure to that causes reduction by losing electrons; oxygen and moisture, reducing the risk of corrosion. therefore it gets oxidized. Silver develops a black coating after some time. Issme batao: Copper develops a green coating after some time. Chapter ka KAZAANA: Balancing (MCQs) Type of Reaction and Example (Specially Decomposition and Redox) Color Change Activities