Quantitative chemistry

• what is law of conservation of mass

  Energy cant be created nor destroyed

  mass of reactants = mass of products
• how to find out Mr

  1. list all atoms of all elements
  2. work out Ar for all elements
  3. multiply Ar of that element with no of that element
  4. Add all the Ars together
• formula to find the percentage of mass of an element

  total Ar of the element/Mr of the compound * 100
• what is 1 mole equal to

  6.02 * 10^23 (Avogrados constant)

  to find out no of atoms do:

  atoms in substance * avogrados constant
• steps in using moles to balance equations

  1. find no. of moles of all substances
  2. divide all of them by the smallest mole in the reaction
  3. the answer is the coefficient of that substance
• Reacting masses step

  1. find moles of known substance
  2. look at the molar ratio of the two substances to find the no. of moles of the unknown substance
  3. do Mr * moles to get the mass of the unknown substance
• steps of calculating limiting reactant

  1. calculate moles of each reactant
  2. look at the ratio
  3. compare the moles
• how to work out concentration in terms of mass and the unit

  concentration = grams/volume

  unit = g/dm^3
• atom economy equation


  Atom economy = Ar of desired product/ Mr of all reactants * 100
• percentage yield equation


  yield = mass of product made/ mass of theoretical yield * 100
• steps of doing titration calculations

  1. use concentration and volume to get moles of the known substance
  2. compare the molar ratio to get the moles of the unknown substance
  3. do moles/volume to get the concentration of unknown
  4. to get concentration in g/dm^3, multiply concentration by Mr