Vivekanand Vellanki

One mole of any compound contains the same number of molecules - this is called the avogadro number. I believe 6.023\ \cdot10^{23}, but the actual number is not important. One mole is equivalent in weight to the molecular mass of the compound.

For e.g. One mole of Hydrogen is 1gm. 1gm of Hydrogen contains N (avogadro number) molecules.

One mole of C-12 is 12gm. 12gm of C-12 contains N molecules.

Do you have a specific question applying this concept?