Mole Concept

• Formula Mass (Weight)


  The sum of the atomic weights of each atom in its chemical formula
• Molecular Mass (Weight)


  If the formula represents a molecule (as with atoms that are chemically bonded together)
• Unit for formula/molecular mass is amu (atomic mass unit)
• Formula mass of water (H2O)

  • 2 × (1.0079 amu) + 1 × (15.9994 amu) = 18.01528 amu
• Formula mass and molecular mass of glucose (C6H12O6)


  • 6 × (12 amu) + 12 × (1.00794 amu) + 6 × (15.9994 amu) = 180.0 amu
• Formula mass of table salt (NaCl)

  • 23.0 amu + 35.5 amu = 58.5 amu
• Moles (mol)


  A measure of the amount of particles in matter, always represented by Avogadro's number 6.02 x 10^23
• Mole


  1 molar mass of any substance contains one mole of particles (ions, molecules, atoms, formula units)
• Molar Mass


  The mass of one mole of a substance, numerically equal to the atomic mass or formula mass, expressed in grams per mole (g/mol)
• Molar mass examples


  • 1 mol Na = 23.0 g Na
  • 1 mol CO2 = 44.0 g CO2
  • 1 mol (NH4)2SO4 = 132.1g (NH4)2SO4
• Mole-to-Mass Conversion


  Given moles, calculate mass in grams using molar mass as conversion factor
• Mole-to-Mass Conversion example


  • 0.400 mol N2 x 28.0 g/mol = 11.2 g N2
• No. of Atoms-to-Moles Conversion

  Given number of atoms, calculate moles using Avogadro's number
• No. of Atoms-to-Moles Conversion example

  • 2.80 x 10^24 atoms Si / 6.02 x 10^23 atoms/mol = 4.65 mol Si
• No. of Moles-to-Atoms Conversion

  Given moles, calculate number of atoms using Avogadro's number
• No. of Moles-to-Atoms Conversion example

  • 0.360 mol Al x 6.02 x 10^23 atoms/mol = 2.17 x 10^23 atoms Al
• Moles-to-No. of Molecules Conversion

  Given moles, calculate number of molecules using Avogadro's number
• Moles-to-No. of Molecules Conversion example

  • 5.0 mol sugar x 6.02 x 10^23 molecules/mol = 3.01 x 10^24 molecules sugar
• No. of Molecules-to-Moles Conversion

  Given number of molecules, calculate moles using Avogadro's number
• No. of Molecules-to-Moles Conversion example

  • 4.65 x 10^24 molecules CO2 / 6.02 x 10^23 molecules/mol = 7.72 mol CO2
• Moles-to-Mass Conversion


  Given moles, calculate mass in grams using molar mass
• Moles-to-Mass Conversion example


  • 2.5 mol CaS x 72 g/mol = 180 g CaS
• Moles-to-Mass Conversion examples


  • 0.0122 mol Si3N4 x 140.3 g/mol = 1.71 g Si3N4
  • 0.0122 mol (CH3)3N x 59.11 g/mol = 0.721 g (CH3)3N