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Chemical reaction and equations(class 10th)

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This an complete overview of class 10 chemistry chapter 1- Chemical Reaction and Equations..

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Chemical reaction and equations(class 10th)

  2. 2. A schematicrepresentationof anychemical reaction withthe help ofsymbolsand formulae of various species is calledchemicalequation Example: Magnesium + 0xygen Magnesium oxide
  3. 3.  Write the correct skeletal equation containing the formulae of only onemolecule of each reactant and product  Start with the compound that has the maximum atoms and the atoms present in it are balanced may bea reactant or a product. Balance the element that appear only onceon each side of the arrow first. Then balance the element which appear more than once  Elementary substance are balancedat the end. If required ,the whole equation is multiplied by some suitable no. In orderto makeall the coefficient whole no. but formulae can not be changedfor balancing
  4. 4. C Forexample : Reaction of calcium with water  Skeletalequation calcium + water calcium hydroxide+ hydrogen  Properequation: Ca(s) +H2o(l) Ca(oh)2 + H2  Balance equations (By Hit and Trial method) a) Count each kindof atom on both sides b) Themost complicated formulaein the above equation is Ca(OH)2 . Theequation is balancedwith respect to Ca,so wecan balance ‘O’ by setting 2 just before h20. Ca +2H2O Ca(OH)2 + H2 Hence, hydrogenis balanced. ATOM LHS RHS Ca 1 1 O 1 2 H 2 4
  5. 5. C (c) Each kind of atom is counted on both the sides again which arenow equal and therefore, the equations is balanced  The names of the various reactant and product  The formulae of the reactant and product.  The relative amount of the reactant and product.  The physical state of the reactant and the product.  Heat change during the reaction.  The specific condition necessary for the reaction
  6. 6. reactan
  7. 7. Thereaction in which two ormore reactants combine to form a single product is known as a combination reaction. + A B AB Magnesium oxide Watch glass Burner Mg ribbon Tong Example:  Burning of Magnesium in air 2Mg + O2 2MgO + Heat
  8. 8.  Quick lime that is Calcium Oxide when reacts vigorsly with water produces slacked lime CaO(s) + H2O Ca(OH)2 (aq) + Heat Beaker Water CalciumOxide  Burning ofcoal C(s) + O2(g) CO2 + Heat
  9. 9. In such reaction ,a single reactant breaks down to givesimplerproduct + AB B A Example :  Lead Nitrate powder onheating decomposes to givebrown fumes of nitrogen dioxide with cracking sound
  10. 10. 2Pb(NO3) 2PbO + 4NO2 +O2 Test tube holder Boiling tube Lead nitrate Burner There arethree types of decomposition reaction :
  11. 11. io When a decomposition reaction is carriedoutby hating , it is called thermal decomposition 2FeSO4 Fe2O3 + SO2 + SO3 If theenergy of thesunlight (in the formofphotons)is usedto carryoutthe decompositionreaction, thenit is called photochemicaldecomposition 2AgCl 2Ag +Cl2
  12. 12. io If electric current isused to carry out decomposition reaction, then it is calledelectrolytic decomposition Example : Electrolysis of water It is the decomposition of water into oxygen and hydrogen when an electric current is passed through water containing few drops of dilute sulphuric acid 2H2O 2H2 + O2
  13. 13. In a displacement reaction , a more reactive elementdisplaces a less reactive element from its compound (generally salt solution) + + less reactive element More reactive element Example: Fe +CuSO4 FeSO4 + Cu
  14. 14. In this reaction , two compounds react by exchangeof ions to form two new compound. In these reaction , generally precipitation occurs. + + Example: On mixing sodiumsulphate(Na2SO4)solutionwith barium chloride(BaCl2) solution, awhite precipitateofbarium sulphate(BaSO4)is formed. Na2SO4 +BaCl2 BaSO4 +2NaCl AB CD AC BD
  15. 15. O Old concept Oxidation: Additionofoxygenor electronegativeelement toasubstanceorremoval ofhydrogenor electropositiveelement fromthesubstanceis called oxidation Reduction: Additionofelectropositiveelement or hydrogenin an element or removalof oxygenor electronegativeelement fromasubstanceis called reduction. CuO+ H2 Cu +H2O Oxidation Reduction
  16. 16. O Modern concept: Oxidation:Loss of electrons from an element orincrease in +veelectrovalency of an element is called oxidation. Reduction:Gain ofelectron by an element (like Na,K,Mg) or removal ofan electronegative element Redox reaction: The reaction in which oxidation and reduction takes place simultaneously are known as redox reaction.
  17. 17. Corrosion:Theslow eating upofmetals bytheactionofair,moistureorachemical ontheir surfaceis called corrosion. (1) Ironarticlesget coatedwithareddish brownpowderwhen leftopen in moistair fora long time .This processis commonlyknownasrusting ofiron 2Fe+ 3/2O2 + XH2O Fe2O3 .XH2O ;whereX = No.of watermolecules Rancidity: Foodmaterialcontainingfator oil whenleft foralong time become rancidi.e.smell andtastechanges.This isbecausetheyget oxidisedwhen theycamein contactwiththe atmosphericoxygen. Thisis called rancidity
  18. 18. Some other reaction……. Polymerization reaction The processin which alargenumberofsimplesmall molecules (monomers) arecombined togetherto formvery large molecule (polymer)is termedaspolymerisation. nA polymerization (A) n monomer polymer Example: nCH2 = CH2 Ethene ( CH2 – CH2 ) Polyethene polymerization
  19. 19. eaction Precipitation reaction Thereaction in which an insoluble substance formedis called as a precipitation reaction and the insoluble substance is called as precipitate Example: NaCl + AgNO3 NaNO3 + AgCl sodium chloride Silver nitrate Sodium nitrateSilver chloride