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What is mole? In chemical reactions, quantities of substances are considered in terms of the number of atoms, ions or molecules present. The unit devised by chemists to express the number of atoms or ions or molecules is called mole (symbol "mol"). A Mole is defined as gram atomic mass, gram molecular mass or gram formula mass of any substances (atoms, ions or molecules) which contains 6.02e+23. entities/particles. A mole is the amount of pure substances containing the same number of chemical units as there are atoms in exactly 12 grams of carbon-12 (i.e, 6.02e+23). Formerly, the connotation of  "mole" was "gram molecular weight". Current usage tends to apply the term "mole" to an amount containing Avogadro's number of whatever unit are being considered. Thus, it is possible to have a mole of atoms, ions, radicals, electrons, or quanta. This usage makes unnecessary such terms as "gram-atom", "gram-formula weig

                                      Molecular Mass The mass of  molecule is referred as its molecular mass. Molecular mass is defined as the sum of the atomic masses of the atoms of all the elements present in a molecule shown by its molecular formula. For example, The molecular mass of H2o is (1 amu)*2+16 amu = 18 amu.                                          Formula Mass In many substances atoms are not organized into discrete molecules but are bonded to one another in a net work and are called Ionic Compounds. Such Compounds are represented by their simplest (Emprical) formulas e.g.NaCl, SiC etc. Formula mass is the sum of the atomic masses of atoms as given in the emprical formula of the substance. Sodium chloride is represented by the simplest formula NaCl which means that in its crystalline form, the sodium ions (Na+) and chloride ions (Cl-) occur in the ratio 1:1. Thus the formula mass of NaCl is 23 amu + 35.5 amu =58.5 amu. The formula mass of silicon carbide S

Atom is an extremely small particle. It is not possible to weigh it directly. Therefore we take its mass by comparing with slected Standard Atomic mass of C-12 (the  stable light isotope of carbon) Atomic mass is defined as the mass of one atom of the element compared with the mass of one atom of C-12. It is a number which tells how heavy or light an atom is as compared to the mass of another atom. The atomic mass of "Mg" is 24 which mean each atom of Mg is twice as heavy as Carbon atom. A Swedish chemist J. Berzelius (1779-1848) determined the atomic masses of elements. Atomic is the average of the masses of all the isotopes of an element with respect to their relative abundance. It is determined by multiplying the masses of all the isotopes which relative abundance and then add them up and finaly divide them by 100. For example:- Average Atomic Mass of Cu =63.55 a.m.u Mass spectrometer is a technique by means of which the relative abundance and atomic mass of th