IIT FOUNDATION
(IX_Ass-3)
MOLE CONCEPT
1) An atom is the smallest indivisible particle of an element that can take part in a chemical change.
2) A molecule is the smallest particle of matter which can exist freely.
3) Atomic weight of element is the number of times that one atom of the element is heavier than 1/12th of C12 atomic weight.
4) The atomic weight of expressed in grams is known as gram atomic weight.
5) Molecular weight of substance expressed in grams is known as gram molecular weight or gram mole.
6) At STP one gram mole of any gas occupies 22.4 lit. it is known as gram molar volume.
7) One gram mole of any substance will contain 6.023x1023 molecules.
8) One gram atom of any element will contain 6.022x1023 atoms.
9) The number of atoms in one gram atom of an element or the number of molecules present in one gram mole of a substance i.e - 6.022x1023 is known as Avogadro’s law
10) The mass of 1 mole of a substance in grams is known as molar mass.
11) The amount of substance containing Avogadro number of chemical units is called one mole.
12) Number of moles ‘n’ = =
13) Weight of a substance containing a definite number of moles = Number of moles x gram molecular weight W= n x M
14) Number of molecules present in a given substance = x Avogadro number = X N
15) Number of atoms = x Avogadro number
16) Number of ions = x Avogadro number
17) Atomicity is the number of atoms in a molecule
18) Rare gases are monoatomic.
19) Gaseous elements H2, F2, Cl2, O2 and N2 are diatomic.
20) Phosphorus is tetra atomic (P4) sulphur molecule is an octa atomic (S8).
21) Molecules of elements are homo atomic.
22) Molecules of compounds are hetero atomic
23) 1 mole =6.023x1023 particles of a substance (atoms or molecules or ions )
= mass of the1 mole of atoms in grams is gram atomic weight
= mass of the 1 mole molecules in grams is gram molecular weight
= 1 mole of any gas at STP occupies 22.4lit volume.