The mole is a unit of measurement for the amount of substance. Moles give us a consistent method to convert between atoms/molecules and grams.
The mathematical expression for calculating moles is expressed as:
We can express moles in terms of molecular mass, number of atoms/molecules and in terms of volume.
· 1 mole of a pure substance has a mass in grams equal to its molecular mass.
- 1 mole contains the same number of particles as there are in 12g of carbon-12 atoms. This number is called Avogadro’s number and is equal to 6.023 × 1023 particles.
- 1 mole of a gas occupies a volume of: 22.4 litres at S.T.P.
For example: 1 mole of sodium atom has mass 23 g. It contains 6.023 × 1023 atoms and occupies 22.4 litres of volume at S.T.P.
Let us solve a simple numerical to understand this concept in a better way.
Calculate the number of particles in each of the 46 g of Na atoms.
In this numerical it is desired to find the number of particles in 46 gm of Na.
We know that one mole of Na contains 6.023 × 1023 particles.
Therefore, we will first find the number of moles in 46 gm of Na.
We know that 1 mole = 6.022 × 1023 particles.
Therefore, 2 moles = 2×6.022 × 1023 particles
= 12.044 × 1023 particles
Hence, 46 gm of Na contains 12.044 × 1023 particles.
To be perfect in the mole concept, try to solve more numerical.
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