A process in which one or more substances (the reactants) are converted to one or more product having different chemical properties is called chemical reaction.
Combination Reaction : The chemical reaction in which two a more than two substances form a new substance (product).
The characteristics of the new substance are quitely different from the original substances (reactants).
e.g. 2Mg + O2 → 2MgO
When magnesium is burnt in the presence of oxygen gas then the white powder of the magnesium oxide (MgO) is formed
Decomposition Reaction : The chemical reaction in which a large chemical compound splits or decomposes into two or more smaller chemical compounds, the characteristics of the newly formed compound (products) are quitely different from the original compound.
e.g. CaCO3 → CaO + CO2 ↑
When calcium carbonate (CaCO3) is heated then calcium oxide (CaO) and carbon dioxide (CO2) are produced.
Displacement Reaction : The chemical reaction in which the
atom of an element replaces the atom of another element from the compound and forms a new compound is displacement reaction. Usually a more active element replaces another, which is less active in the compound.
e.g. Zn + CuSO4 → ZnSO4 + Cu ↓
When the pieces of zinc are mixed in the solution of copper sulphate (CuSO4), zinc replaces copper and zinc sulphate (ZnSO4) is formed and along with it copper is precipitated.
Isomerisation Reaction (Rearrangement Reaction) : The chemical reaction in which the atoms of the molecule of a compound is accommodated in such a way that molecular formula of the original (old) and new compound are same.
e.g. NH4CNO → NH2CONH2
The isomerisation of ammonium cyanate (NH4CNO) and urea (NH2CONH2)
Endothermic Reaction : The chemical reaction in which heat is absorbed is called an endothermic reaction.
e.g. N2 + O2 → 2NO - 43.2 kcal
To form nitric oxide (NO) by the combination of nitrogen and oxygen.
Exothermic Reaction : The chemical reaction in which heat is released is called an exothermic reaction.
e.g. 2H2 + O2 → 2H2O + 136.74 kcal
To form water (H2O) by the combination of hydrogen and oxygen.
Reversible Reaction : The chemical reaction which proceeds in both directions is called reversible reaction.
e.g. 3Fe + 4H2O ⇌ Fe3O4 + 4H2
When the water vapour is supplied on the red heated iron, then ferrosoferric oxide (Fe3O4) and hydrogen are formed.
Irreversible Reaction : The chemical reaction which proceeds in only one direction is called irreversible reaction.
e.g. 2KCIO3 → 2KCI + 3O2
