CC9

• Calculating empirical formula from masses of reactants


  1. Symbol for element

  2. Mass (g)

  3. Relative atomic mass, A

  4. Divide the mass of each element by its relative atomic mass

  5. Divide the answers by the smallest number to find the simplest ratio
• Empirical formula

  The ratio of each type of atom to another
• Molecular formula

  The actual number of atoms of each type in a molecule
• Relative formula mass


  The mass of each atom in a molecule added together
• Mass is conserved in a reaction, so the mass of the reactants is the same as the mass of the products (when careful to not let anything like a gas escape)
• Calculating moles of a substance

  1. number of moles of substance = mass of substance (g) / A or M

  2. concentration = mass of solute in g / volume of solution in dm³
• If we increase the mass of solute and keep the volume the same


  We increase the concentration
• If we increase the volume of solution and keep the mass of the solute the same


  We decrease the concentration