Types of Reactions.pptx

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 + O 2  → 2MgO (Magnesium burns with a dazzling white flame to form magnesium oxide) Sodium Combines with Chlorine to form Sodium Chloride Na + Cl 2 → 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 )

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