C3 - Quantitative Chemistry

• The total mass of all substances is conserved in a chemical reaction
• The atoms that go in must come out, so we must balance equations
• Relative atomic mass (RAM)


  The mass of an atom relative to the mass of a carbon-12 atom
• Relative formula mass (RFM)


  The sum of the relative atomic masses of the atoms in a compound
• CO2 has a relative formula mass of 12 + 2 x 16 = 44
• Some reactions produce a gas product which, if it leaves the reaction vessel, will result in a seeming decrease in mass of the reactants
• Mole


  A specific number of atoms or molecules, used to compare amounts of substances
• If you have as many grams of a substance as its relative atomic or formula mass, you have one mole
• Moles


  Calculated as g / RAM or RFM
• In the methane combustion reaction, two oxygen molecules are needed per one molecule of methane
• Calculating the mass of a product from the mass of a reactant

  Mass -> Moles -> Moles -> Mass
• Stoichiometry


  The ratio of moles of one substance to another in a reaction
• The concentration of a solution can be given in g per dm^3 or mol per dm^3
• Percentage yield


  The amount of product actually made compared to the theoretical maximum
• Atom economy


  The mass of the desired product divided by the total mass of reactants, times 100
• One mole of any gas takes up a volume of 24 dm^3 at room temperature and pressure
• The total mass of reactants is the same as the total mass of products due to conservation of mass