chap 7 - mole concept and stoichiometry

• • relative atomic mass (Ar) --> average mass of an atom of an element when compared with 1/12 of the mass of a carbon-12 atom
  • relative molecular mass (Mr) --> average mass of a molecule of a substance when compared with 1/12 of the mass of a carbon-12 atom
• mass of an atom = mass of proton + mass of neutrons in the atom

  = nucleon no.

  = mass no.
• Ar - relative atomic mass

  Mr - relative molecular mass (covalent)

  - relative formula mass (ionic)
• mole

  • unit = quantity

  > 1 pair = 2

  > 1 dozen = 12

  > 1 ream = 500 piece

  > 1 mole = 6.02 x 10²³

  • mole is the unit to count atoms, molecules and ions
  • symbol = mol
• molar mass

  • no. of moles = mass/ molar mass (Mr)
  • molar mass = mass of 1 mole of any substance