TYPES OF CHEMICAL REACTIONS
Chemical reactions are classified into four types in accordance with the nature and the numbers of the reactants and the products.
Combination reaction
Decomposition reaction.
Displacement reaction.
Double displacement reaction.
There are four types of chemical reactions
1.Composition reaction.
When two or combine in a reaction to form a single product is called a combination reaction.
A + B→ AB
ACTIVITY 1 -: take a small amount of hydrochloric acid in a test tube. heat the test tube. dip a glass rod in the ammonia solution and hold it on the top of the test tube. you will observe white smoke emanating from the tip of the glass rod.
What must have happened?
Due to heating HCL vapours started coming out from the test tube, and NH3 gas comes out from the solution on the glass rod. The ammonia gas and hydrogen chloride gas reacted to form the salt ammonium chloride in a gaseous state first, but immediately due to the condensation process at room temperature, it got transformed into the solid state. as a result white smoke was formed. the chemical equation is
NH3(g)+HCL(g) → NH4Cl(s)
Ammonia+ hydrogen chloride → ammonium chloride
Ex,
2Mg + O → 2MgO
Magnesium oxide is formed as a single product by a combination of magnesium and oxygen.
CaO + H2O → Ca(OH)2 + Heat
Calcium hydroxide is formed as a single product by a combination of calcium oxide and water.
2.Decomposition reaction
The chemical reaction in which two or more products are formed from a single reactant is called ‘Decomposition reaction’
AB → A + B
Activity-: take some sugar in an evaporating dish and heat it with the help of a burner . after some time you will see the formation of a burnt-out black substance. Exactly what must have happened in this activity?
In the above activity, a single reactant sugar is divided into two substances (C and H2O)
C12H22O11 → 12 C +11H2O
Ex,
1.CaCO3 → CaO(s) + CO2
2.2H2O2(l) → 2H2O(l) + O2
3. Displacement reaction.
The reaction in which the place of the ion of a less reactive element in a compound is taken by another more reactive element by the formation of its own ions is called displacement reaction.
AB + C → AC + B
Ex,
1.CuSO4(aq) + Zn (s) → ZnSO4(aq) + Cu(s)
Zinc is more reactive then copper.
2.CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)
Iron is more ractive then copper.
4.Double displacement.
The reaction in which the ions in the reactants are exchanged to form a precipitate are called a double displace ment reaction.
AB +CD → AD + BC
Ex,
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