Atomic and Molecular Masses
Atomic and Molecular Masses:
The smallest particle of an element, which may or may not have independent existence is called an atom, while the smallest particle of a substance which is capable of independent existence is called a molecule.
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 = 1.66056×10–24 g.
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. 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.
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.
Formula Mass:
Sum of atomic masses of the elements present in one formula unit of a compound. It is used for the ionic compounds.
Mole 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.
Percentage Composition:
The mass percentage of each constituent element present in any compound is called its percentage composition.
Mass % of the element = (Mass of element in 1 molecule of the compound/Molecular mass of the compound) x 100
Study Material