Mole Chemistry

You must hear about mole concept in chemistry that is basis of stoichiometry. Let’s first discuss what is a Mole in Chemistry? The amount of pure substance having the same number of atoms as in 12 grams of carbon-12 is known as one mole. In Chemistry Mole  is equals to 6.023 X 1023 or Avogadro number.

Now first question comes to your mind that what is a Mole? Mole definition states that the number of atoms in exactly 12 g of 12C is known as one mole. All stoichiometry is essentially based on the Mole Chemistry.

Amedeo Avogadro performed an experiment in 1811 and concluded that at the same temperature and pressure, equal volumes of gases contain equal numbers of molecules.

Hypothetically he purposed that number known as Avogadro number; 6.02 X 1023 or 602 000 000 000 000 000 000 000. Hence one mol of anything has 6.02 x 1023 particles such as one mole of silver contains 6.02 x 1023 atoms of silver.

Let’s take a simple example of calculation of mols present in compound such as water. A of mol of water contains 6.02 x 1023 molcules weighs 18 gm. Hence a mol is a collection of atoms with a mass equal to the atomic weight in grams.

Mole of an element is directly related to atomic weight or atomic mass formula of that element. For example; the atomic weigh of lithium is 6.941amu, it means 6.941 grams of lithium contains 6.02 x 1023 atoms of lithium.

The mole concept can be used for the relation between the number of particles and the mass of a substance. Let’s do an example for that. Calculate the number of atoms present in 0.24 mol of sodium. As we known, in one mole of sodium there are 6.02 × 1023 atoms. Therefore in 0.24 mols of sodium contain 0.24 x 6.02 × 1023 = 7.22 x 1022 atoms of sodium.
The best way to express the atomic mass of any substance in grams is known as molar mass. The only change is in their units. Such as the atomic mass of iron is 55.85 amu and molar mass is 55.85 g/mole. For diatomic molecules the molar mass units is just double to its atomic mass. Like the molar mass of oxygen is 32.00 g/mol and atomic mass is 16.00 amu. The molar mass of polyatomic compounds is the sum of molar mass of each atom. Let’s calculate the molar mass of magnesium nitrate, Mg(NO3)2 is sum of atomic mass of Mg, 2N and 6O.
Molar mass of Mg(NO3)2 = 24.31 + 2(14.01 + 16.00 + 16.00 + 16.00)
=24.31 + 2(62.01) = 148.33
The relation between molar mass, mol and number of particle can be written as;
6.02 × 1023 particles = one mol = molar mass