Page 1 :
2/20/22, 10:10 PM, , In a chemical reaction, at least one of the following will occur:, Change in state, Change in colour, Evolution of a gas, Change in temperature, Formation of a precipitate, , A chemical equation is the symbolic representation of a chemical reaction in the form of chemical formulae, signs, symbols, and directions. In which the reactant, entities are given on the left-hand side and the product entities on the right-hand side.Balanced chemical equation, • Reactants →Products, LHS, RHS, Total number of atoms on the LHS = Total number of atoms on the RHS, • How to balance an equation, • Write reactants and products, • Balance the maximum number of a particular atom on both sides, • Balance other atoms, • A complete balanced equation should look like, , CO(g)+2H2(g)340 atm−−−−→CH3OH(l)COg+2H2g→340 atmCH3OHl, , Types of reactions, • Combination reaction, Two or more reactants combine to form one single product., ​Examples, , C(s)Carbon+O2(g) Oxygen→ CO2(g)Carbon dioxide2H2(g)Hydr, CaO(s)Calcium oxide (Quick lime)+ H2O(l) Water→ Ca(OH)2(aq)Calcium hydroxide (Slaked lime), CaOsCalcium oxide(Quick lime)+H2OlWater→CaOH2aqCalcium hydroxide(Slaked lime)CsCarbon+O2gOxygen→CO2gCarbon dioxide2H, • Exothermic reaction – Heat gets released in the reaction. Most combination reactions are exothermic. For example,, , CaOsCalcium oxide(Quick lime)+H2OlWater→CaOH2, CaO(s)Calcium oxide (Quick lime)+ H2O(l), , Water→ Ca(OH)2(aq)Calcium hydroxide, , (Slaked lime), , • Endothermic reaction – Heat is absorbed in the reaction. Very few combination reactions are endothermic. For example,, 12 N2(g)+O2(g)→NO2(g)12N2g+O2g→NO2g• Decomposition reaction, A single reactant breaks into several simple products., Examples, , 2FeSO4Ferrous sulphate, , −→, , CaOCalcium oxide+CO2, , Δ, , −−−→ Fe2O3Ferric oxide+SO2+SO3 CaCO3Limestone, , 2AgClSilver chloride, , Δ, , Δ, , −−, , −−, , 1/2
Page 2 :
2/20/22, 10:10 PM, , 2FeSO4Ferrous sulphate→, , Δ Fe2O3Ferric oxide+SO2+SO3CaCO3Limestone→, , Δ CaOCalcium oxide+CO22Ag, , −→2Ag Silver+Cl2, ​• All decomposition reactions are endothermic [they absorb heat]., , • Displacement reactions:, ​In displacement reactions, a more reactive metal can displace a less reactive metal from their compounds in aqueous solutions. (However, a less reactive metal, cannot displace a more reactive metal.), Example:, , CuSO4Copper Sulphate, , (Blue), , + ZnZinc → ZnSO4Zinc Sulphate (Colourless) + CuCopper (Red) Fe(s) Iron + CuSO4(aq)Copper sulphate →, CuSO4Copper Sulphate(Blue)+ZnZinc→ZnSO4Zinc Sulphate(Colourless)+CuCopper(Red)FesIron, , Cu(s) Copper + FeSO4(aq) Iron sulphate, • Double displacement reaction, ​Exchange of ions occurs between two compounds., Example, , Na2SO4 (aq) + BaCl2 (s) → BaSO4 (aq) + 2NaCl (s)Sodium sulphate Barium chloride Barium sulphate Sodium chloride, Sodium sulphate Barium chloride Barium sulphate Sodium chloride, •W, ​ hen the aqueous solution of two compounds react by exchanging their respective ions, such that one of the products formed is insoluble salt and, , appears in the form of a precipitate, then the reaction is said to be precipitation reaction., • When an acid solution reacts with a base and the two exchange their respective ions, such that only salt and water are products, then the reaction is, , called neutralisation reaction., •W, ​ hen two compounds react with each other and displace their ions, in such a manner that one of the product formed either decomposes into gaseous, , compounds or is formed in gaseous state, then the reaction is called gas-forming reaction., • Oxidation → When a substance gains oxygen or loses hydrogen, , • Oxidation in everyday life, Corrosion – When a metal is oxidised by the action of air and moisture [that’s why metals are coated], Rancidity – When fats and oils are oxidised, their smell and taste change [that’s why food is kept in air-tight containers], Reduction → When one substance loses oxygen or gains hydrogen, , • Redox – Oxidation–reduction reaction, , Download, PDF, , 2/2
