CHEMICAL REACTIONS AND TYPES OF CHEMICAL REACTIONS CLASS 10 SCI CH-1

What is Chemical Reaction?

The process in which different atoms breaks and makes bonds between them to produce new substances is called Chemical reaction. 

Now, chemical reactions are generally written in chemical equation.

 

So, What is Chemical Equation?

Chemical equation is the representation of a chemical reaction in which reactants are written on the left-hand side and products are written on the right-hand side with an arrow mark(→) between them.

Now, What types of Reactions are there?

There are generally nine types of reactions. They are as follows:

(1)Combination Reaction

(2)Decomposition Reaction, in it there are three types:(1)Thermal Decomposition 

(2)Electrolytic Decomposition 

(3)Photochemical Decomposition 

(3)Displacement Reaction 

(4)Double Displacement Reaction 

(5)Oxidation Reaction 

(6)Reduction Reaction 

(7)Redox Reaction 

(8)Exothermic Reaction 

(9)Endothermic Reaction

 1. COMBINATION REACTION: A reaction in which two or more substances combine with each other to form a single substance is called Combination reaction. 

This reaction can be summarised as 

      X + Y → XY

Example: (1) CaO + H2O → Ca(OH)₂+ Heat

whem CaO(quick lime) reacts with H2O(water) its give Ca(OH)₂ (slaked lime) with heat.

2. DECOMPOSITION REACTION: A reaction in which a single substance breakdown to give simpler products is called Decomposition reaction. 

This reaction can be summarised as

      XY → X + Y

Example: (1) CaCO₃ (heat)→ CaO + CO₂

when CaCO₃(limestone) is heated it decomposes to give CaO(quick lime) and CO₂(carbon-dioxide).

Decomposition reaction has three types (1) THERMAL DECOMPOSITION: The decomposition of one substance to two or more substances by heating is called Thermal decomposition. 

Example:(1) 2Pb(NO₃)₂ (heat)→ 2PbO + 4NO₂ + O₂ 

when Pb(NO₃)₂ (lead nitrate) is heated it gives PbO( lead oxide) and NO₂ (nitrogen dioxide) and O₂ (oxygen).

(2) ELECTROLYTIC DECOMPOSITION: The decomposition of one substance to two or more substances by electricity is called electrolytic decomposition. 

Example: (1) 2H₂O (electricity) → 2H₂ + O₂

when 2H₂O(water) gets electrolysis it gives 2H₂(hydrogen) and O₂(oxygen).

(3) PHOTOCHEMICAL DECOMPOSITION: 

The decomposition of one substance to two or more substances in the presence of light is called Photochemical decomposition. 

Example: (1) 2AgCl (sunlight)→ 2Ag + Cl₂

when 2AgCl(silver chloride) is put in sunlight it gives 2Ag(silver) and Cl₂ (chlorine). 

3. DISPLACEMENT REACTION: The reaction in which more reactive metal displaces less reactive metal and takes its place is called Decomposition reaction. 

This reaction can be summarised as

    XY + Z → ZY + X

Example:(1) Zn + CuSO₄ → ZnSO₄ + Cu

when Zn(zinc) reacts with CuSO₄(copper sulphate) more reactive meat zinc replaces copper to give ZnSO₄(zinc sulphate) and cu(copper).

4. DOUBLE DISPLACEMENT REACTION: 

The reaction in which two reactants exchange ions between them is called Double Displacement reaction.

This reaction  can be summarised as 

    WX + YZ → WZ + XY

Example:(1) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

when Na₂SO₄(sodium sulphate) reacts with BaCl₂(barium chloride) both changes ions between them to give BaSO₄(barium sulphate) + 2NaCl(sodium chloride).

5. OXIDATION REACTION: The reaction in which a substance gains oxygen and loses hydrogen is called Oxidation reaction. 

Example:(1) 2Cu + O₂ (heat)→ 2CuO 

when 2Cu  reacts with O₂, Cu oxidised and gives 2CuO.

6. REDUCTION REACTION: The reaction in which a substance loses oxygen and gains hydrogen is called Reduction reaction. 

Example:(1) CuO + H₂ (heat)→ Cu + H₂O

when CuO reacts with H₂, CuO gets reduced and gives Cu and H₂O.

7. REDOX REACTION: The reaction in which one substance gets oxidised and another substance gets reduced is called Redox reaction. 

Example:(1) ZnO + C → Zn + CO

when ZnO reacts with C, ZnO gets reduce and C gets oxidised and gives Zn and CO.

8. EXOTHERMIC REACTION: The reaction in which heat is produced during the formation of product is called an exothermic reaction. 

Example:(1) CH₄ + 2O₂ → CO₂ + 2H₂O

when CH₄ reacts with O₂ it gives CO₂ and H₂O with heat.

9. ENDOTHERMIC REACTION: The reaction in which heat is absorbed during the formation of product is called an endothermic reaction. 

Example:(1) 2AgBr (sunlight)→ 2Ag + Br₂ 

when AgBr is put in sunlight it absorbs heat and give Ag and Br.

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