5.6 - Solutions for Quantitative Analysis

• what accurate chemicals analysis involves

  preparing a solution of an unknown sample
• titration

  a volumetric analysis technique for finding the concentrations of solutions and for investigating the amounts of chemicals involved in reactions
• how to accurately measure volumes in titrations

  using pipettes, burettes and graduated flasks
• standard solution

  a solution with an accurately known concentration

  makes volumetric analysis possible
• method of preparing a standard solution

  dissolve known mass of chemical in distilled water then make the volume of solution up to a definite volume in a graduated flask
• chemicals appropriate for preparing a standard solution

  must be very pure

  must not gain or lose mass when in air

  must have a high molar mass so weighing errors are minimised
• primary standard

  a chemical which can be weighed out accurately to make up a standard solution
• reasons for doing quantitative dilution

  make a solution with the concentration needed for an experiment from standard solution

  to dilute an unknown sample to give a suitable concentration for titration
• method for quantitative dilution

  take a measured volume of a more concentrated solution with a pipette and run it into a graduated flask and fill it to the mark with distilled water
• relationship between 2 dilutions

  CªVª = CºVº

  c: concentration

  v: volume
• moles of a chemical taken from a concentrated solution

  concentration × volume