Gravimetric analysis Flashcards
Steps of weighing by difference?
- A clean dry weighing boat is weighed empty then the sample is added to it.
- The accurate mass of the weighing boat and its contents is then measured and recorded.
- Sample from the weighing boat is then transferred to the container to be used in the experiment. Gentle tapping on the base of the weighing boat will ensure the bulk of the sample is transferred, but it is unimportant if traces of the sample remain
- Weighing boat and residual material are accurately weighed and the masses recorded.
- The accurate mass of the sample transferred is the difference between the 2 recorded masses.
Weighing accurately approximately?
Measuring a substance to an approximate target mass while recording its exact mass with high precision. This ensures accurate calculations in experiments, even if the initial estimate is not exact.
Heating to a constant mass
- heating a substance
- allowing to cool in a desiccator to prevent absorption of water
- weighing
- repeating the steps of heating, cooling and weighing until no further changes in mass are observed
Gravimetric analysis is used to?
Determine the mass of an element or compound in a substance.
How does gravimetric analysis work?
The substance is converted into another substance of known chemical composition, which can be readily isolated and purified.
The conversion can occur either through precipitation or volatilisation.
Precipitation conversion?
the substance undergoes a precipitation reaction. The precipitate is separated from the filtrate and the filtrate tested to ensure the reaction has gone to completion. The precipitate is washed, dried to constant mass and then weighed.
Volatilisation conversion?
The substance is heated and any volatile products (often water) are evaporated. The substance is heated to constant mass and the final mass recorded
