C3 Quantitative Chemistry

• Law of Conservation of Mass

  Matter cannot be created or destroyed, Themassof the products isequalto that of thereactants.Some reactants may give a change in mass but this is because somegas has escaped
• Relative atomic mass


  The average mass of that element compared to carbon 12
• Relative formula mass


  The sum of all of the masses in a given formula
• Uncertainty


  The interval of which the true value must lie
• Mole


  contains 6.02 x 10^23 atoms
• Limiting Reactant


  The reactant which is completely used up limits the reat of the reaction
• excess reactant


  the reactant which is not used up
• Concentration


  A measure of the number of particles in a given volume
• decimeter^3 (dm^3)


  Measurement of volume contains 1000cm^3
• Calculating percentage uncertainty


  uncertainty/quantity being measured x 100
• The equation which links mols, mass of chemical and relative formula mass (equation)

  
• The equation which links concentration, moles and volume (equation)

  
• The equation which links mass, volume and concentration (equation)

  
• Concentration (equation)


  Mass/volume or Moles/volume
• How to calculate moles

  Number of particles / avocado constant - or mass/Mr or Ar
• Mr


  Relative formula mass
• Ar


  Relative atomic mass
• Half equation


  can be shown what happens to 1 reactant in a reaction
• Ionic equation


  can be used to simplify complicated equations - they just show the species involved in the reaction. Spectator ions not included.
• Spectator ions


  ions that do not participate in a reaction
• species


  different atoms and molecules that participate in a reaction
• Number of moles


  mass of a substance/atomic or formula mass
• 24dm^3


  the amount of volume 1 mole any gas takes up at room temperature.
• volume


  amount (mol) x 24dm^3
• amount of a substance

  mass/atomic mass
• calculating number of moles using Avogadro's number

  number of atoms/Avogadro's number

  
• Percentage yield (formula)

  
• Atom economy (definition)


  is a measure of the amount of reactant that ends up as useful product
• Atom economy (formula)

  
• Percentage yield (definition)


  used to compare actual yield obtained from a reaction with maximum theoretical yield
• a good atom economy is...

  ... where most of the reactants end up as the desired product
• high atom economy is important because...

  ...it is important for sustainable development because it is more efficient
• Why might actual yield be less than theoretical yield?

  - if the reaction is reversible it might not go to completion

  - some product could be lost when separated from reaction mixture

  - the reactants may react in different ways to the expected reaction
• Addition reaction


  all the reactant molecules end up as the desired product
• sustainable development


  has a high atom economy, as there are more products and less waste produced. Needs to meet the needs of current generations without compromising the ability of future generations.
• reaction pathway


  shows the change in energy during a chemical reaction
• choosing a reaction pathway


  comparing the atom economy of 2 different reaction pathways, these factors include;

  - atom economy

  - cost of reactants

  - the percentage yield

  - the rate of the reaction

  - the equilibrium position

  - the usefulness of the biproducts
• Volume Of A Gas (Room Temperature)

  Volume = Number of moles x 24
• Isotopes


  same element, different number of neutrons, so it has a different atomic mass
• moles of gas


  Volume/24