The mole and number of particle

The number of particles in matter is measured in mole

Definition: The amount of substance that contains as many particles as the number of atoms in exactly 12 g of carbon-12

Symbol of mole : mol

How many atoms are there in 12 g of carbon-12?

= 6.023 x 10^23

• The value of 6.023 x 10^23 is called the Avogadro constant or Avogadro number

• Avogadro constant, NA is the number of particles in one mole of a substance

point to note :

1 mol of any subtances contain 6.023 x 10^23 particles(atom,molecule,unit of ions)

Example

A closed glass bottle contains 0.5 mol of oxygen gas, O2. How many oxygen molecules, O2 are there in the bottle?

The number of oxygen molecules, O2 = 0.5 mol

number of mole x NA

= 0.5 mol × 6.02 × 10^23 mol-1

= 3.01 × 10^23 molecules