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The concept of mole is extremely useful in chemistry. The mole is a term like dozen. Dozen means 12. The mole means 6.02 x 1023. It is convenient for chemists to use a concept like mole which represents such a large number since they deal in very small and very numerous quantities. The mole is also called Avogadro’s number.
Avogadro’s number: It is the number of molecules present in 22.4 liters of a gas at STP. Its value is 6.02 x 1023. It is denoted by N.
All the atomic masses are determined relative to the mass of carbon-12. The mass of one mole of any element is simply its atomic mass taken in grams. For example the mass of one mole of carbon is 12 grams. In other words 6. 02 x 1023 atoms of carbon have a mass of 12 grams.