Molecular Mass, Formula Mass, Gram Atomic Mass, Gram Formula Mass

                                     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 SiC is 28 amu + 12 amu=30 amu.
             

                                  Gram Atomic Mass

When Atomic mass of an element is expressed in grams, it is called Gram Atomic Mass.
For example :
Gram atomic mass of Carbon = 12 g
Gram atomic mass of Sodium = 23g

                                                  Gram atom

The mass equal to gram atomic mass of an element is known as Gram atom.
For example:
1 Gram atom of Carbon = 12g
2 Gram atom of Carbon = 2*12g= 24g
1 Gram atom of Sodium = 23g
2 Gram atom of Sodium = 2*23g= 46g
                    

                                Gram Molecular Mass

When molecular mass of a molecule is expressed in grams it is called gram molecular mass.
For example:
Gram Molecular Mass of CO2=12g +(16g)*2= 44g.

                                                Gram Molecule

The mass equal to gram molecular mass of a molecule is knowns as Gram molecule.
For example:
1 Gram molecule of CO2 = 44g
2 Gram molecule of CO2 = 44*2= 88g.

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