The Mole Concept

  • the extreme smallness of atoms and molecules makes it necessary to define a very large “standard sample”
  • it is referred to as the MOLE
  • it’s the SI base unit for amount of chemical substance
  • one mole consists of 6.02 x 1023 atoms or molecules; it is known as Avogadro’s Number
  • the mass of one mole of an element is the same as the atomic mass of the element

For example:
one mole of bromine, atomic mass 79.90 amu, has a mass of 79.90 g; this is called the molar mass

the molar mass of chromium, Cr, is 52.00 g/mol.

Types of Calculations:


(i) mass of 1.50 moles of chromium

(ii) # of moles in 5.00g of O2

(iii) determining the molar mass of a compound; what is the molar mass of CuSO4?

(iv) # of moles given a particular mass of a compound; how many moles is 56.00 g of NaCl?

(v) mass of a compound given a particular # of moles; determine the mass of 0.1 moles of H2SO4.