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Combination Reaction Examples

Combination reaction:

When two or more substances chemically bonded together to produce a single product, it is called as combination reaction or synthesis reaction. When the bond forms between the elements, heat is released; this is because the reactions are usually exothermic.


 Mercuric Oxide on Heating


Combination reaction types:


1. Reaction between two elements

Ex: C + O2`->` CO2

Here the carbon is completely burnt in oxygen which results in carbon dioxide 

2. Reaction between two compounds

Ex: CaO + H2O `->` Ca ( OH)2

Here the calcium oxide (lime) combined with water gives calcium hydroxide which also known as slaked lime.

3. Reaction between an element and compound

Ex: O + H2O `->` H2O2

Here oxygen which is an element combined with water which is a compound gives hydrogen peroxide.


Examples for combination reaction:


1. Na2 + H2O `->` 2NaOH

Here sodium oxide is combined with water gives sodium hydroxide.

2. 4Li + O2 `->` 2Li2O

Here lithium is combined with oxygen to form lithium oxide.

3. 2Mg + O2 `->` 2 MgO

Here magnesium is combined with oxygen to form magnesium oxide.

4. H2 + Cl2 `->` 2 HCL

Here hydrogen is combined with chlorine to form hydrochloride.

5. NH3 + HCl `->` NH4Cl

Here colorless ammonia is added to colorless hydrogen chloride gives ammonia  chloride.

6. 2H2 + O2 `->` 2 H2O

Here hydrogen is burned in the air or oxygen produces water.

7. S + O2 `->` SO2

Here sulphur is burned in the air to produce sulphur dioxide.

8. Ba + F2 `->` Ba F2

Here barium metal and fluorine gas is combined to produce salt barium fluoride which is highly exothermic reaction.

9. MgO + CO2 `->` MgCO3

Here magnesium oxide is combined with carbon to produce magnesium carbon dioxide.

10. 2Al + 3Br `->` 2AlBr3

Here aluminum is combined with bromine which produces 3 + aluminum iron and 1+bromine iron.


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Other Reactions:


Chemical reactions are of the following six types:

1)Combustion reaction: It is a type of reaction in which oxygen combines with the other compound and forms carbon dioxide (CO2) and water (H20)

Ex:  C10H8 + 12 O2 -----------> 10 CO2  + 4 H2O

       CH4 + 2 O2 --------------->  CO2 + 2 H2O

2)Synthesis Reaction: It is a type of chemical reaction in which two or more simple substances combine to form one single complex substance.

Ex:  C +  O2 ---------->  CO2

        CaO + H2O -----------> Ca(OH)2

3) Decomposition Reaction: It  is a type of chemical reaction in which a complex substance breaks down to simpler substances.It is opposite of synthesis reaction.

Ex: 2 N2O5 ----------> 4 NO2 + H20

      2 KClO3  -------------> 2 KCl  + 3 O2

4) Single displacement reaction : It is a chemical reaction in which an element displaces another element in a compound .

 Ex:  Mg + 2 HCl  -----------> MgCl2 +H2  

        Fe2O3 + Zn ------------> Zn2O3 + 2 Fe  

5) Double displacement reaction:This is a type of chemical reaction in which the anions and cations in the reactants interchange their positions and form two different compounds.

Ex:  2 NaCl +H2SO4 -------------> Na2SO4 + 2 HCl

       AgNO3 + KCl ---------------> AgCl + KNO3

6) Acid - Base reaction: It is a type of double displacement reaction in which acid and base react to form salt and water.

Ex:  HCl + NaOH -------------> NaCl + H20

      H2SO4 + 2  NaOH ----------> Na2SO4 + 2 H2O

7) Isomerisation : It a type of chemical reaction  in which a chemical compound undergoes a structural rearrangement without any change in its net atomic composition.

8) Disproportionation : Its a type of chemical reaction in which a single reactant forms two products with different oxidation states.

Ex: Pb+2 ------------> Pb + Pb +4. here in the products lead has 0 and +4 oxidation states.