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# Experiment 16: Gravimetric Analysis for AP Chemistry

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By McGraw-Hill Professional
Updated on Feb 8, 2011

For a quick review on stoichiometry, refer to the following concepts:

### Synopsis

The amount of a substance present in a sample is determined by taking a solution containing that substance and precipitating a compound containing that substance. The precipitate is then dried and weighed. (See the Stoichiometry chapter.)

### Equipment

analytical balance
beaker(s)
crucible and cover
desiccator
drying oven
funnel
Meker burner
support stand
triangle crucible support

### Measurements

1. A sample is weighed and then dissolved.
2. Excess (unmeasured) reactant is added to the solution to form a precipitate.
3. The empty crucible and cover are weighed.
4. The crucible and cover containing the dried precipitate are weighed.

### Calculations

The mass of the precipitate is found as the difference between measurements 3 and 4.

The mass of the dried precipitate is converted into moles by using the molar mass. Through use of a stoichiometric ratio, the moles of precipitate are converted to the moles of the substance of interest. The moles of this substance are converted to its mass using the molar mass.

The mass of the substance of interest divided by the mass of the sample and then multiplied by 100% gives the percent of a substance in the sample.

Common precipitates used include AgCl and BaSO4.

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