Chemical Reaction & Equation

1. Chemical Reaction &
Equation

2. What is chemical reaction
• The transformation of chemical substance or material into a
new chemical substance or material by making and breaking of
bonds between different atoms is known as Chemical
Reaction
Eg. Burning of magnesium to make magnesium oxide

3. Reactant and Product
• Those substance which take part in reaction are called reactant and
those which are formed after reaction are called product.
• For example when we burn magnesium, magnesium and oxygen is
reactant and magnesium oxide is product
Magnesium + Oxygen Magnesium oxide
Reactant Product

4. Characteristic of Chemical Reaction
• Evolution of a Gas
• Formation of a precipitate
• Change in colour
• Change in temperature
• Change in state

5. Evolution of a Gas
• Some reaction are characterized by the evolution of gas
For eg:-
1. When Zinc react of Dilute sulphuric acid it form zinc sulphate and
evolution of hydrogen gas take place
2. When sodium carbonate react with dilute hydrochloric acid it form
sodium chloride carbon dioxide and water.

6. Formation of Precipitate
• A Precipitate is a solid product which separates out from the solution
during a chemical reaction. Some chemical reaction are categorized
by formation of a precipitate.
For Eg. Potassium Iodide and lead nitrate react and form yellow ppt of
lead iodide.
• When sulphuric acid and barium chloride react they form white ppt of
barium sulphate

7. Change inn Colour
• When purple colour potassium per magnate react with citric acid its
colour change purple to colourless
• When turmeric come In contact of ay ase its colour change yellow to
red

8. Change In Temperature
• After the chemical reaction some time there is a change I temperature if the
reactant absorb heat for reaction we call it endothermic reaction whare as if
the heat is released after reaction it is called exothermic reaction
Eg:- 1. When quick lime is soaked in water it make slake lime and heat is
generated so it is a exothermic reaction
2. When Zinc granule is added dilute sulphuric acid react hey form zinc
sulphate ad heat is generated
3. Barium hydroxide ad ammonium chloride reach together to fprm barium
chloride ammonia and water and the temp. fall down of solution shows it is
endo thermic reaction

9. Change in state
• Eg. Hydrogen and oxygen are gas when the react and make water
which is liquid
• Burning the solid wax make carbon di oxide gas water vapor and

10. Chemical Equations
• The method of representing a chemical reaction with the help of
symbols and formulae of the substances involved in it is known as a
chemical equation.
• Zinc + Sulphuric acid Zinc Sulphate + hydrogen gas
This is known as word equation
Zn+ H2SO4 ZnSO4 + H2
This is known chemical equation

11. Balanced & Unbalanced Chemical Equation
A Balanced chemical equation has an equal number of atom of
different elements in the reactant and the products.
Zn+ H2SO4 ZnSO4 + H2
2Mg + O2 2MgO

12. • Unbalanced Reaction has unequal no of atom of lemet in reactant
and product
• H2 + O2 H2O
• CO2+ H2O C6H12O6+ O2

13. Balancing the chemical equation
• Balancing the both side of equation is known as balancing the
chemical equation
FeCl3 + MgO ---> Fe2O3 + MgCl2
Li + H3PO4 ---> H2 + Li3PO4
ZnS + O2 ---> ZnO + SO2
FeS2 + Cl2 ---> FeCl3 + S2Cl2
Fe + HC2H3O2 ---> Fe(C2H3O2)3 + H2
HCl(aq) + MnO2(s) ---> MnCl2(aq) + Cl2(g) + H2O(ℓ)
Fe2O3(s) + C(s) ---> Fe(s) + CO2(g)
CO2 + S8 ---> CS2 + SO2

14. Type of Chemical Reaction
• Combination Reaction
• Decomposition Reaction
• Displacement Reaction
• Double Displacement Reaction
• Oxidation and reduction reaction

15. Combination Reaction
• When Two or more reactant combine to form single product are
called combination reaction

16. Decomposition Reaction
• When one substance split to form two or more substance it is called
decomposition reaction. It is just opposite of combination reaction

17. Displacement Reaction
• Those reaction in which one element take place of another element
in a compound are known as displacement reaction

18. Why Some element displace another element
• In Displacement reaction a more reactive element displace a less
reactive element from its compound

19. Double displacement reaction
• Those reaction in which two compound react by exchange of ions to
form new compound are called double displacement reaction

20. Oxidation and reduction reaction
• When in any reaction if a substance is gained oxygen or loss hydrogen
it is said to be oxidized where are when it loss oxygen or gain
hydrogen it is said to be reduced.
• CuO + H2 Cu + H2O
• ZnO + C Zn + CO
• MnO4 +4HCl MnCl2 + 2H2O + Cl2
• H2S + Cl2 2HCl + S
• 2Al + Fe2O3 Al2O3 + 2Fe
• Those who are oxidized are called reducing agent and those who get reduce are
called oxidizing agent

21. Effect of oxidation reaction in daily life
• Corrosion of metals
• Rancidity

22. Corrosion
• Corrosion is the process in which metals are eaten up gradually by the
action of air, moisture or a chemical such as acid on their surface
For eg. Rusting of iron metal is the most common form of corrosion
4Fe + 3O2+2xH2O 2Fe2O3.xH2O
Rusting of Iron is a redox reaction
Corrosion weeknes the Iron and steel objects ad structure such as

23. Rancidity
• The condition produced by aerial oxidation of a fat and oils in food
marked by unpleasant smell and taste is called ancidity