Chemical Reactions and Equations PDF

# Chemical Reactions and Equations ## Chemical Reactions - It is a chemical process in which new substances with new properties are formed due to re-arrangement of atoms. - Change can be physical or chemical - **Physical:** - No new products are formed - It is a temporary chan...

# Chemical Reactions and Equations ## Chemical Reactions - It is a chemical process in which new substances with new properties are formed due to re-arrangement of atoms. - Change can be physical or chemical - **Physical:** - No new products are formed - It is a temporary change - It is a reversible reaction - Change in physical properties like colour, shape, size, etc. - Examples: Melting of candle, cutting of trees, boiling of water, etc. - **Chemical:** - New products are formed - It is a permanent change - It is an irreversible reaction - Change in chemical properties like composition of the compound - Examples: Respiration, Digestion, growth of plant or animal, Rusting of iron, etc... ## Activity 1.1 - Burning of magnesium ribbon in air - Cleaning a magnesium ribbon about 3 to 4 cm by rubbing with sand paper. - Why do we rub the magnesium ribbon with sand paper? - To remove the oxide layer and thereby helping in the complete burning of Mg (Magnesium is exothermic reactive metal). - When magnesium ribbon is exposed to air for a long time a layer of Magnesium Oxide (MgO) is normally formed on the surface of the metal because oxygen present in air slowly combines with the metal to form Magnesium Oxide. - The oxide layer never burns when a flame is brought nearer to metal. So the surface should be properly cleaned with a sand paper before burning. - Why should we keep burning magnesium for away from our eyes? - Burning of magnesium is highly exothermic reaction, it liberates high amount of heat and light - What do you observe in above activity? - The magnesium ribbon burns with dazzling white flames and forms white powder; This powder is magnesium oxide (MgO). - Write the reaction when Mg reacts with oxygen. - 2Mg(s) + O2(g) → 2 MgO(s) (Amorphous Powder). - Note: Basic in Nature ## Activity 1.2 - Lead nitrate reacts with Potassium iodide - Write the balanced equation for the above reaction activity. - Pb(NO3)2 + 2KI → 2KNO3 + PbI2 - Name the type of reaction. - Double displacement reaction and also called as precipitation reaction - Why is it called precipitation reaction? - When 2 compounds are mixing with each other by exchanging their radicals, one of the formed product is insoluble (precipitate) so it is called precipitation reaction. ## Activity 1.3 - Action of Sulphuric Acid on Zinc granules. - Write the balanced equation for the above activity? - Zn + H2SO4 → ZnSO4 + H2 - Write the observation for the above activity? - Liberation of gas bubbles around the zinc granules - Name the gas evolved in the above reaction and writes the test for it. - The liberated gas is hydrogen. - Test: When burning splinter is brought near to the gas, it burns with pop sounds. ## Change in Colour: - 2 Pb(NO3)2 → PbO + 4NO2 + O2 ## Evolution of Gas - Zn + CuSO4 → ZnSO4 + Cu - Zn + 2HCl → ZnCl2 + H2 - 2K + 2H2O → 2KOH + H2 ## Change in Temperature - CaO + H2O → Ca(OH)2 - N2 + O2 → 2NO ## Chemical Equation - It is a shortened representation with the help of symbols form and formula of the substances involved in it. ## What is unbalanced equation? - In a chemical equation, if the number of reactants or mass of reactants is not equal to the number of products formed or the mass of the products formed is called unbalanced equation and is also called as skeletal equation. ## What is balanced equation and which law governs the law of balancing of equations?