Rapid Revision - Chemical Reactions and Equations PDF

- RAPID REVISION - Chemical Reactions and Equations  Rapid Revision First watch One Shot Chemical Reaction: The transformation of chemical substance into another chemical. substance. e.g. Rusting of iron, the setting of milk into curd. Chemical Eq...

- RAPID REVISION - Chemical Reactions and Equations  Rapid Revision First watch One Shot Chemical Reaction: The transformation of chemical substance into another chemical. substance. e.g. Rusting of iron, the setting of milk into curd. Chemical Equation: Representation of chemical reaction using symbols and formulae of the substances A+B→C+D Reactant Product Mg + O2 → MgO Make equations more informative: Physical states - solid (s), liquid(l), gas(g), aqueous solution (aq). Concentration of acid - Concentrated (conc.) Dilute (dil.) Heat changes - Reactant(s) -> Product(s) + Heat Reactant(s) + Heat -> Product(s) Conditions to yield products - Kuch important terms: Precipitate: is the insoluble solid which settles down after the completion of the chemical reaction. Exothermic reactions: The chemical reactions that release heat energy. Endothermic reactions: The chemical reactions in which heat energy is absorbed. Catalyst: A catalyst is a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction. e.g. Formation of ammonia (Haber’s Process) - Fe (+ve catalyst) Characteristics of Chemical Reaction: i. Change in Colour ii. Change in temperature (heat is generated) iii. Change in State: (i.e. from gas to liquid) iv. Evolution of Gas: v. Formation of Precipitate vi. Endothermic reaction (photosynthesis also) (digestion and vi. Exothermic reaction respiration also) Balanced Chemical Equation: number of atoms of each element in reactants = number of atoms of each element in products Law of Conservation of Mass: Mass of reactants = Mass of products “ Mass is neither created nor destroyed in a chemical reaction. ” Balancing ke Balance these: questions bohut important h! Types of Chemical Reactions: 1.Combination Reaction: Two or more reactants combine to form single products. A + B → AB Carbon The most effective way to test for CO2 is to bubble the gas through lime water, dioxide Test which is a diluted solution of calcium hydroxide. 2.Decomposition Reaction: A single reactant decomposes to form two or more products. AB → A + B  Decomposition Reaction Thermal Decomposition Photolytic Decomposition (initiated by thermal energy) (initiated by absorbing energy from photons) black and white photography Electrolytic Decomposition (initiated by electrical energy) Hydrogen Hydrogen (cathode) will produce a popping sound when a burning candle is brought close. Test Oxygen (anode) will make the flame of the candle burn brighter. Anode orr cathode kisse lenge yaad rakhna!  3.Displacement Reaction chemical reaction in which a more reactive element displaces a less reactive element from its compound. Single Displacement A + BC → AC + B Double Displacement AB + CD → AD + CB Reactivity Series: Secret trick to remember  Magnesium ribbon burns with a dazzling white flame and changes into a white powder (magnesium Oxide) Take some lead nitrate solution in a A yellow precipitate of lead iodide forms, and the test tube or beaker and add potassium solution changes color from colorless to yellow. iodide solution Take some zinc granules in a conical Bubbles of hydrogen gas will form around the zinc flask and add sulfuric acid. metal. The reaction releases heat along with the gas. Calcium oxide reacts vigorously with water to produce slaked lime (calcium hydroxide), releasing a large amount of heat. Originally green 🡢 Color changes to white, then brown (ferric oxide) 🡢 smell of burning sulfur. Brown fumes of nitrogen dioxide gas are released, oxygen also present, Yellow lead monoxide solid remains🡢appears reddish-brown when hot and yellow when cold. White silver chloride turns grey in sunlight. Deep blue color of the solution fades to light green, and the iron nail becomes covered with a red-brown layer of copper A white precipitate will form. Forms a black substance CuO. Hydrogen gas can be passed over the CuO causing a reverse reaction. Redox Reactions: Oxidation + Reduction Oxidation: + oxygen or - hydrogen Reduction: - oxygen or + hydrogen Oxidizing agent: An oxidizing agent is a substance that causes oxidation by accepting electrons; therefore, it gets reduced. Reducing agent: A reducing agent is a substance that causes reduction by losing electrons; therefore it gets oxidized. Effects of oxidation in daily life: Corrosion: metals are gradually destroyed by chemical reactions with substances in their environment, such as moisture and acids. Examples: Rusting of iron, Tarnishing of silver, Green coating on copper Prevention: Coating metals with protective layers (e.g., paint or galvanization) helps prevent direct exposure to oxygen and moisture, reducing the risk of corrosion. Silver develops a black coating after some time. Ag + H 2 S Ag 2 S + H 2 Copper develops a green coating after some time. Cu + H 2 O + CO2 + O 2 CuCO 3.Cu(OH) 2 Effects of oxidation in daily life: Rancidity: the spoilage of fats and oils in food, leading to unpleasant taste and smell. Examples: Spoiled butter, Old cooking oil, Stale chips Prevention: Adding antioxidants, storing foods in airtight containers, and refrigerating can help slow down or prevent the oxidation process and, consequently, rancidity Class 10th Phodenge!