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MOLE CONCEPT (GRADE 9)


It is found that 1 g atom of any substance contains the same number of atoms and 1 g molecule of any substance contains the same number of molecules. This number is found to be 6.022× 10^23 and is known as Avogadro's number. Avogadro's number is represented by Na.

 

A mole is a chemist's unit of counting particles such as atoms, molecules, ions, etc. which represents a value of 6.022×10^23 just as a dozen for 12, etc. are used to count different objects. 

A mole of hydrogen atoms means 6.022×10^23 atoms of hydrogen whereas a mole of hydrogen molecule means 6.022×10^23 molecules of hydrogen or 2×6.022×10^23 atoms of hydrogen.

A mole of oxygen molecule means 6.022×10^23 molecules of oxygen or 2×6.022×10^23 atoms of oxygen. 

 

A mole is defined as the amount of substance which has mass equal to its gram atomic mass if the substance is atomic or gram molecular mass if the substance is molecular.

1 mole of carbon atoms= 12 grams 

1 mole of oxygen atom= 16 grams 

1 mole of oxygen molecule= 32 grams 

1 mole of water molecule= 18 grams

1 mole of carbon dioxide molecule= 44 grams 

 

A mole is defined as the amount of substance  that contains Avogadro's number of atoms if the substance is atomic or Avogadro's number of molecules if the substance is molecular.

1 mole of carbon atoms= 6.022×10^23 atoms of carbon

1 mole of oxygen atom= 6.022×10^23 atoms of oxygen

1 mole of water molecule= 6.022×10^23 molecules of water 

 

In case of gases, a mole is defined as the amount of gas which has a volume of 22.4 litres at STP.

1 mole of oxygen gas= 22.4 litres of oxygen gas at STP 

1 mole of carbon dioxide gas= 22.4 litres of carbon gas at STP. 

 

A mole of an ionic compound is defined as the amount of substance which has mass equal to gram formula mass or which contains Avogadro's number of formula units (6.022×10^23).

 

1 mole of NaCl= 58.5 grams of NaCl = 6.022×10^23 formula units of NaCl

 

 


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