Types of Chemical Reactions for secondary classes

1. TYPES OF
CHEMICAL
REACTIONS
- Alwin S Joy
X-C
Roll no 4

2. TYPES OF CHEMICAL
REACTIONS

3. 1.Combination Reaction
• Those reactions in which two or more substances
combine to form a single substance, are called
combination reactions.
• In a combination reaction, two or more elements
can combine to form a compound ; two or more
compounds can combine to form a new compound
; or an element and a compound can combine to
form a new compound.

4. Examples:-
• Magnesium and oxygen combine, when heated, to form
magnesium oxide
2Mg + O2 → 2MgO
(Magnesium burns with a dazzling
white flame to form magnesium oxide)
• Sodium Combines with Chlorine to form Sodium Chloride
Na + Cl2 → NaCl
(Reaction of Sodium and Chloride
is a highly exothermic reaction)

5. 2. Decomposition Reaction
• Those reactions in which a compound splits up
into two or more simpler substances are
known as decomposition reactions.
• The decomposition reactions are carried out by
applying heat, light or electricity. Heat, light or
electricity provide energy which breaks a
compound into two or more simpler
compounds.
• A decomposition reaction is just the opposite
of a combination reaction.

6. Examples:-
• When ferrous sulphate is heated strongly, it decomposes to form ferric
oxide, sulphur dioxide and sulphur trioxide.
2FeSO4​(s)→ Fe2​O3​(s)+SO2​(g)+SO3​(g)
[THERMAL DECOMPOSITION]
• When electric current is passed through acidified water, it decomposes
to give hydrogen gas and oxygen gas.
2H2O (l) → 2H2 (g) + O2 (g)
[ELECTROLYTIC DECOMPOSITION]

7. • When silver chloride is exposed to light, it decomposes to
form silver metal and chlorine gas
2AgCl (s) → 2Ag (s) + Cl2 (g)

8. 3. Single Displacement Reaction
• Those reactions in which a more reactive element
replaces a less reactive element from it’s compound is
called a single displacement reaction
Here C is more reactive than A so it displaces A from it’s
compound

9. Examples:-
• Iron metal reacts with dilute hydrochloric acid to form iron (II) chloride and
hydrogen gas :
Fe (s) + 2HCl (aq) → FeCl2 (aq) + H2 (g)
(FeCl2 Solution)
• When iron (III) oxide is heated with aluminium powder,
then aluminium oxide and iron metal are formed
Fe2O3 (s) + 2Al (s) → Al2O3 (s) + 2Fe (l)
(The displacement reaction between
iron (III) oxide and powdered aluminium
produces so much heat that iron metal
obtained is in molten form)

10. 4.Double Displacement Reactions
• Those reactions in which two compounds
react by an exchange of ions to form two
new compounds are called double
displacement reactions.
• A double displacement reaction usually
occurs in solution and one of the products,
being insoluble, precipitates out (separates
as a solid).

11. Examples:-
• When barium chloride solution is added to sodium sulphate solution,
then a white precipitate of barium sulphate is formed along with sodium
chloride solution
BaCl2 (aq) + Na2SO4 (aq) → BaSO4 (s) + 2NaCl (aq)
(White precipitate of Barium Sulphate)
• When hydrogen sulphide gas is passed through copper sulphate solution,
then a black precipitate of copper sulphide is formed alongwith sulphuric
acid solution
CuSO4 (aq) + H2S (g) → CuS (s) + H2SO4 (aq)
(Black precipitate of Copper Sulphide)

12. THANK YOU !!