What is Decomposition Reaction and Combination Reaction?
In a decomposition reaction, a single reactant breaks down to form two or more products. On the other hand in combination reactions two or more reactants combine to form a single product.
That is the reason why decomposition reaction is called the opposite of combination reaction.
Examples of Decomposition Reaction
Calcium carbonate on heating decomposes to give calcium oxide and carbon dioxide.
CaCo3 (s)————- CaO (s) + CO2
In this reaction calcium carbonate is decomposed into calcium oxide and carbon dioxide.
When electric current is passed through water, it decomposes to give Oxygen and hydrogen.
2 H2O (l)————————— 2H2 (l) + O2 (g)
In this reaction water is decomposed into hydrogen and oxygen.
Examples of Combination Reaction
CaO (s) + H2O (l)————— Ca(OH)2 (aq) + heat
In this reaction calcium oxide combines or reacts vigorously with water to form calcium hydroxide( slaked lime). Lot of heat is produced during this reaction.
Reaction between hydrogen gas and Oxygen gas
2H2 (g) + O2 (g) —————- 2 H2O (l)
In this reaction hydrogen and oxygen combine to form water.