Gravimetric Analysis

• What does the tare function do on a balance?

  Resets balance to 0g
• What does "weighing accurately approximately" mean?

  Weighing around a known set value
• What calculation is performed in weighing by difference to determine the weight of contents?

  Final mass - initial mass = weight
• What is gravimetric analysis used to determine?

  Mass of an element or compound in a substance
• In gravimetric analysis, what processes are used to convert the substance into another substance?

  Precipitation or volatilisation
• What happens to volatile products during volatilisation conversion in gravimetric analysis?

  They are evaporated
• In volatilisation conversion, what is the substance heated to?

  Constant mass
• What type of chemical reaction is used in precipitation reaction?

  2 solutions -> solid
• In precipitation, what is added and what happens after the solid forms?

  Excess of one solution, filter, dry
• What is given off in volatilisation?

  Gas
• In volatilisation, what is heated to dryness?

  Hydrated salt
• What are the steps for heating to constant mass?

  • Heat a substance
  • Allow to cool in a desiccator
  • Weighing
  • Repeat heating, cooling, weighing until no further change
• What does "weighing accurately approximately" mean?

  Close to, but not exactly, specific mass
• In precipitation conversion, what happens to the precipitate after the precipitation reaction?

  Separated, tested, washed, dried, weighed
• What does a desiccator not do?

  Dry
• What does a desiccator allow hot solids to do?

  Cool without absorbing water
• What do empirical formulae represent?

  Simplest whole number ratio
• What does vacuum filtration provide?

  Faster means of separating
• What funnels can be used during vacuum filtration?

  Buchner, hirsch or sintered glass
• What are the steps to calculate water of crystallisation?

  • Calculate the mass of reactant
  • Calculate n of reactant
  • Calculate mass of water
  • Calculate n of water
  • Work out ratio
• What are the steps to calculate empirical formulae?

  • Calculate n = m / gfm
  • Identify Smallest number of moles
  • Divide by the smallest number
• in gravimetric analysis a substance is converted into another substance of known _____ ______ which can be .....

  chemical composition, readily isolated and purified