Table of Contents
Atomic Mass Unit
One atomic mass
unit is defined as a mass exactly equal to one twelfth the mass of one
carbon -12 atom. And 1 amu = 1.66056×10–24g.
Today, ‘amu’ has
been replaced by ‘u’ which is known as unified mass. Atomic Mass
Atomic mass of an
element is defined as the average relative mass of an atom of an element
as compared to the mass of an atom of carbon -12 taken as 12.
Gram Atomic Mass
The quantity of an
element whose mass in grams is numerically equal to its atomic mass. In
simple terms, atomic mass of an element expressed in grams is the gram
atomic mass or gram atom.
For example, the atomic mass
of oxygen = 16 amu
Therefore gram atomic mass of oxygen = 16 g
Molecular Mass
Molecular mass of
a substance is defined as the average relative mass of its molecule as
compared to the mass of an atom of C-12 taken as 12. It expresses as to how
many times the molecule of a substance is heavier than 1/12th of the mass
of an atom of carbon.
For example, a molecule of carbon dioxide is 44 times heavier than 1/12th of the mass of an atom of carbon. Therefore the molecular mass of CO2 is 44 amu. It is obtained by adding the atomic masses of all the atoms present in one molecule.
Gram
Molecular Mass
A quantity of
substance whose mass in grams is numerically equal to its molecular mass
is called gram molecular mass. In simple terms, molecular mass of a
substance expressed in grams is called gram molecular mass.
e.g., the molecular mass of oxygen = 32 amu
Therefore, gram molecular mass of oxygen = 32
g
111Formula Mass
Sum of atomic
masses of the elements present in one formula unit of a compound. It is
used for the ionic compounds.
111Mole Concept.
Mole is defined as
the amount of a substance, which contains the same number of chemical
units (atoms, molecules, ions or electrons) as there are atoms in exactly
12 grams of pure carbon-12.
A mole represents a collection
of 6.022 x1023( Avogadro's number) chemical
units.. 111The mass of one mole of a substance in grams is called its molar
mass. Molar Volume
The volume
occupied by one mole of any substance is called its molar volume. It is
denoted by Vm. One mole of all gaseous substances at 273 K and 1 atm
pressure occupies a volume equal to 22.4 litre or 22,400 mL. The unit of
molar volume is litre per mol or millilitre per mol
