Mole concept


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A mole is defined as quantity of a given substance that contains as many molecules or formula units as the number of atoms in exactly 12g of carbon-12.

The number of atoms in 12-g   sample of  carbon-12 is called Avogadro's number which is 6.02 x 1023.

Terms mole like a dozen refers to a perticular number of things.A dozen egg equals 12 eggs and a mole of ethanol equals 6.02 x 1023 molecules.

1 mole of H atoms =  6.02 x 1023 H  atoms

1 mole O atoms = 6.02 x 1023   O atoms

1 mole H2 molecules = 6.02 x 1023  H2 molecules

1 mole H2O molecule = 6.02 x 1023  H2O molecules

In using terms moles for ionic substances we mean the number of formula units of substance.For example,

A mole of sodium carbonate,Na2CO3 is a quantity containing 6.02 x 1023 Na2CO3 units.But each formula units of Na2CO3 contains two Na+ ion and one CO32- ion.So, a mole of Na2CO3 also contains

2 x 6.02 x 1023  Na+ ion  and 1 x  6.02 x 1023   CO32- ion

Mole and Molar mass

A mole represents not only a specific number of particles but also a definite mass of a substance as represented by its formula.