Question

Define
1. Combination reaction
2. Decomposition reactions and types
3. Displacement reaction
4. Double displacement reaction

And also give examples ​

Answer 1

✰ Combination Reaction :

The Reaction in which two or more reactants are combined together to form a new single product.

Example :

Calcium oxide reacts vigorously with water to produce slaked lime (Calcium Hydroxide) realising a large amount of heat.

† CaO(s) + H2O (l) → Ca(OH)2 (ag) + ∆

Here, CaO and H2O are two reactants which are forming a single product i.e, Ca(OH)2. Heat is also released (∆).

Types of Combination Reaction :

1. Exothermic Reaction = The Reaction in which the heat is released during chemical reaction along with the products.

Example : Burning of natural gas.

† CH4 (g) +2O2 (g) → CO2 (g) + 2H2O (g)

2. Endothermic Reaction = The Reaction in which energy is absorbed i.e, it requires energy to take place in the form of heat, light or electricity.

Example : Reaction of Barium Hydroxide and Ammonium chloride.

† Ba(OH)2 + NH4Cl → 2BaCl2 + NH4OH

✰ Decomposition Reaction :

It is defined as the chemical reaction in which a single reactant breaks down to give two or more substances.

Example :

† H2O (l) → 2H2 (g) + O2 (g)

Types of Decomposition Reaction :

1. Thermal decomposition : The decomposition which decomposition is carried out by heating the reactant.

Example : When 2g of ferrous sulphate crystal are heated in a boiling tube, it get decomposes into two products i.e, Ferric oxide (Fe2O3), sulphate dioxide (SO2) and sulphur trioxide (SO3).

† 2FeSO4 (s) → Fe2O3 (s) + So2 (g) + SO3 (g)

2. Electrolysis Decomposition : The chemical reaction in which decomposition takes place due to electric current.

Example : † H2O (l) → 2H2 (g) + O2 (g)

This process is called electrolysis process in which breakdown or decomposition of substances occur when, direct electric current is passed through the solution and reaction take place at electrodes.

3. Photo decomposition : The decomposition reaction carried out due to sunlight is called photo decomposition (energy of light).

Example : When silver chloride is placed in a China dish under sunlight, white silver chloride turns grey and decomposes into silver and chlorine by light energy.

† 2AgCl (s) → 2Ag (s) + Cl2 (g)

✰ Displacement Reaction :

It is defined as the reaction in which an element is displaced by another element from its reaction is called displacement reaction.

Example : When an iron nail (Fe) is kept in copper sulphate solution (CuSo4) for 20 minutes, the iron nail turns into brownish colour. As the formation of iron sulphate occurs (FeSo4), solution of copper sulphate becomes faded.

† Fe (s) + CuSo4 (aq) → FeSo4 + Cu (s)

✰ Double displacement reaction :

It is the chemical reaction in which two different atoms or group of atoms are naturally exchange is called double displacement reaction.

Example : When a solution of sodium sulphate (Na2So4) is mixed with the solution of Barium Chloride (BaCl2), a white coloured substances which is insoluble in water (BaSo4) is formed and the other product formed is sodium chloride (NaCl2) which remains in the solution.

† Na2So4 (ag) + BaCl2 (aq) → BaSo4 (s) + 2NaCl (aq)

★ The white coloured substance formed as BaSo4 which is insoluble is water is known as Precipitate.