6. Balancing a chemical equation:-
Step 1. Balance the polyvalent ions, if any present of the both side i.e. reactant and product.
Step 2. Balance metals.
Step 3. Balance non-metals.
Step 4. Remove fractions, if any.
7. Types of Chemicalemical Reaction:-
Chemical reactions can be classified in following types:
• Combination Reactions.
• Decomposition Reactions.
• Displacement Reactions.
• Double Displacement Reactions.
• Oxidation and Reduction Reactions.
a) Combination Reactions.
Reaction in which two or more reactants combine to form one product.
Represented as: A + B -> AB
Ex) C + O2 -> CO2
Carbon Oxygen Carbon
dioxide
CaO + H2O -> Ca(OH)2
Calcium Water Calcium
Oxide Hydroxide
b) Decomposition Reactions.
Reactions in which one compound decomposes in two or more compounds or element.
Represented as: AB -> A + B
Ex). CaCO3 -> CaO + CO2
Calcium Calcium Carbon
Carbonate Oxide dioxide
Pb(NO3)2 -> PbO + NO2 + O2
Lead Nitrate Lead Nitrogen Oxygen
Oxide dioxide
Reaction in which compound is decomposed because of heating is called as Thermal Decomposition Reaction.
Electricity
H2O -> H2 + O2
Water Hydrogen Oxygen
Reactions in which compounds decompose into simpler compounds because of passing of electricity is called as Electrolytic Decomposition.
Sunlight
AgCl -> Ag + Cl2
Silver Silver Chlorine
Chloride
Reactions in which a compound Decomposes because of sunlight is called as Photolysis or Photo Decomposition Reaction.
c) Displacement Reaction.
Reactions in which atoms or ions move from one compound to other compound.
It is also known as Substitute Reaction or Single displacement / Replacement Reaction.
Represented as:. A + BC -> AC + B
Displacement reaction takes place only when 'A' is more reactive than B.
Ex) Zn + HCl -> ZnCl2 + H2
Zinc Hydrochloric Zinc Hydrogen
Acid Chloride
Zn + CuSO4 -> ZnSO4 + Cu
Zinc Copper Zinc Copper
Sulphate sulphate
d). Double Displacement Reaction.
Reactions in which ions are exchanged between two reactants.
Represented as: AB + CD -> AD + CB
Ex) BaCl2 + Na2SO4 -> BaSO4 + NaCl
Barium Sodium Barium Sodium
Chloride Sulphate Sulphate Chloride
Double Displacement reaction, in which precipitate is formed, is known as precipitation reaction.
Neutralisation reaction are also examples of double Displacement reaction.
Exothermic and Endothermic Reaction:-
Reaction in which energy is released is called exothermic reaction.
Reaction in which energy is absorbed is called endothermic reaction.
Most of the combination reactions are endothermic.
Most of the decomposition reaction are exothermic.
Respiration is a decomposition reaction in which energy is released.
When quick lime ( calcium carbonate) is added to water, it Decomposes and released energy.
Cooking involves chemical reactions which are endothermic as cooking is possible because of heating.
e). Oxidation and Reduction Reaction.
Oxidation:
Addition of oxygen (Or) Removal Hydrogen.
The compound or element which undergoes oxidation is called
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