Displacement reaction examples/CBSC Class 8 NOTES

Displacement reaction examples



  • Chemical properties of and non-metals are divided into five categories : REACTION WITH OXYGEN, REACTION WITH WATERREACTION WITH ACIDS, REACTION WITH BASESand DISPLACEMENT REACTION .




◆METALS=Most metals combine with oxygen to form metal oxides.




 •sodium react very fast with oxygen that is present in the air to Form sodium oxide . As a result it catches fire if it left in open.  It is, therefore,kept immersed in Kerosene.

  • 4Na    +       O2      =    2Na2O    

Sodium + oxygen = sodium oxide

  •magnesium, on heating , 

burns in air (oxygen)with a dazzling white light to form magnesium oxide. 

  2Mg     +      O2    =    2MgO 

 Magnesium + oxygen = magnesium oxide

 The metallic oxides formed are basic in nature and it turn red litmus solution into blue.

 ◆NON-METALS = Non-metals like carbon , sulphur and phosphorus react with oxygen to form non-metals oxides . 

These oxides are also called acidic oxides as they are form acid when they dissolved in water.




•when carbon burns in air (oxygen) it form carbon dioxide


  • C       +     O2       =       SO2

  • Carbon + oxygen = carbon dioxide


• when sulphur burns in air  (oxygen) it form a pungent, suffocating gas called sulphur dioxide.


  • S       +       O2     =     SO2


  • Sulphur + Oxygen = sulphur  dioxide


When These oxides dissolve in water they form acids , and they turn blue litmus solution into red .


  • CO2    +     H2O   =    H2CO3


  • Carbon dioxide + water = carbonic acid


  • SO2      +        H2O        =      H2SO3


  • Sulphur dioxide + water = sulphurous acid


METALS = Most metals react with water to produce a metal hydroxide or metal oxide and hydrogen gas .

Metal + water  =  Metal hydroxide + hydrogen gas

  • Metal + water = metal oxide +  Hydrogen gas—


sodium reacts violently with cold water and it form sodium hydroxide along  with  hydrogen gas. 

  • A large  amount of heat is evolved in this reaction , which results in hydrogen catching fire.


  • 2Na   +    2H2O     =     2NaOH     +      H2
  • Sodium + water = sodium hydroxide + hydrogen gas


•Metals sach as copper , silver , and gold do not react with water under any conditions .

◆NON-METALS = Non-metals do not react with water


  • Iron and many other metals react with oxygen and moisture  present in the atmosphere .This phenomenon is called corrosion.


  •  The process of slow wearing away of a metal due to the attack of atmospheric gases and moisture on its surface

• Whan Iron reacts with OXYGEN and MOISTURE present in the atmosphere it form a brown ,flaky substance called RUST.

  •  Rusting of iron is an undesirable reaction because the layer of rust formed falls off , exposing the metal to further rusting .


  •  As a result , iron objects get very weak with the passage of time .

• The copper objects get coated with a green substance called basic copper carbonate with the passage of time . 

This happens because Copper reacts with carbon dioxide and moisture that is present in the atmosphere.

•  When Silver objects become blackened and lose their sheen with the passage of time this happens  because  silver react with HYDROGEN SULPHIDE GAS that is present in the atmosphere.


◆METALS = When metal reacts with an acid , it produced salt and hydrogen gas .       


SALTS are  compounds formed when a metal replaces hydrogen in an acid .

Different acids react with different metal and they form different salts.

•  When Zinc reacts with sulphuric acid it form zinc sulphate and hydrogen gas.

  • Zn    +    H2SO4  =   ZnSO4      +     H2
  • Zinc + sulphuric acid = zinc sulphate   + hydrogen gas

• When magnesium reacts with sulphuric acid it form magnesium. Sulphate and hydrogen gas .

  • Mg   +   H2SO4   =   MgSO4  +  H2

  • Magnesium + sulphuric acid = Magnesium sulphate   +   Hydrogen gas

•. When Aluminium reacts with hydrochloride acid  it form aluminium chloride and hydrogen gas .

  • 2Al     +    6HCl   =   2AlCl3    +    3H2


  • Aluminium + hydrochloride acid  
  • = Aluminium chloride + Hydrogen gas

With some metals , the reaction is very fast and vigorous , while with other it may be slow .Some metals do not react with acids at all.

◆NON-METALS = Non-metals , generally do not react with acids at all .


◆METALS = Most metals do not react with bases. 
Only some such as aluminium,zinc,and lead react 
with the solution of strong bases like sodium 
hydroxide and then they produce a compound 
of that met and hydrogen gas.

◆NON-METALS = Non-metals react with bases 
and their reaction with bases are complex .
 So, you will learn about them in higher class.

In a displacement reaction,
When a metal reacts with salt solution 
then it’displaces’ (or replaces ) the 
metal present in it.
We can understand displacement reactions 
on the basis of reactivity series of metals.
The list of reactivity series is given below.

displacement reaction examples
displacement reaction examples


  • This means that a metal which is placed higher in the reactivity series is more reactive than those placed below it . 
  • We can predict whether or not a displacement reaction will take ace by looking at the reactivity series .
  •  A metal will only react with a salt solution if it is placed higher in the reactivity series than the metal in the salt . 
  • For example , iron, which is placed higher in the reactivity series than copper , reacts with copper sulphate 
  • Solution . Copper , however, dose not react with iron sulphate as it is less reactive  than iron .
• silver dose not react with zinc sulphate .
  • Ag   +   ZnSO4  =  No reaction
  • Silver + zinc sulphate = No reaction

• Zinc reacts with copper sulphate to form zinc sulphate and copper .
  • Zn    +    CuSO4  =  ZnSO4    +   Cu
  • Zinc + copper sulphate = Zinc sulphate  + Copper
•  Silver dose not react with copper sulphate.
  • Ag    +     CuSO4      =     No reaction
  • Silver + copper sulphate = No reaction .
  • Form the above reaction, we can conclude that the order of reactivity of zinc , copper , and silver is : Zn , Cu , Ag ( i.e., zinc is most reactive of the three and silver is the least reactive ). 
  • You can verify this from the table that is already given.
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